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USB On-The-Go

(OTG)

Section 27. USB On-The-Go (OTG)

HIGHLIGHTS

This section of the manual contains the following major topics:

27.1 Introduction .................................................................................................................. 27-2

27.2 Control Registers ......................................................................................................... 27-4

27.3 Operation ................................................................................................................... 27-36

27.4 Host Mode Operation................................................................................................. 27-51

27.5 Interrupts.................................................................................................................... 27-59

27.6 I/O Pins ...................................................................................................................... 27-62

27.7 Operation in Debug and Power-Saving Modes.......................................................... 27-64

27.8 Effects of a Reset....................................................................................................... 27-66

27.9 Related Application Notes.......................................................................................... 27-67

PIC32 Family Reference Manual

27.1 INTRODUCTION

The PIC32 USB OTG module includes the following features:

• USB Full-Speed Support for Host and Device

• Low-Speed Host Support

• USB On-The-Go (OTG) Support

• Integrated Signaling Resistors

• Integrated Analog Comparators for VBUS Monitoring

• Integrated USB Transceiver

• Transaction Handshaking Performed by Hardware

• Endpoint Buffering Anywhere in System RAM

• Integrated Bus Master to Access System RAM and Flash

• USB OTG module does not require the PIC32 DMA module for its operation

The USB OTG module contains analog and digital components to provide a USB 2.0 full-speed

and low-speed embedded host, full-speed device, or OTG implementation with a minimum of

external components. This module in Host mode is intended for use as an embedded host and

therefore does not implement a UHCI or OHCI controller.

The USB OTG module consists of the clock generator, the USB voltage comparators, the trans-

ceiver, the Serial Interface Engine (SIE), a dedicated USB Bus Master, pull-up and pull-down

resistors and the register interface. A block diagram of the USB OTG module is presented in

Figure 27-1.

The clock generator provides the 48 MHz clock, which is required for USB full-speed and

low-speed communication. The voltage comparators monitor the voltage on the VBUS pin to

determine the state of the bus. The transceiver provides the analog translation between the USB

bus and the digital logic. The SIE is a state machine that transfers data to and from the endpoint

buffers, and generates the hardware protocol for data transfers. The USB Bus Master transfers

data between the data buffers in RAM and the SIE. The integrated pull-up and pull-down resistors

eliminate the need for external signaling components. The register interface allows the CPU to

configure and communicate with the module.

Note: This family reference manual section is meant to serve as a complement to device

data sheets. Depending on the device variant, this manual section may not apply to

all PIC32 devices.

Please consult the note at the beginning of the “USB On-The-Go (OTG)” chapter

in the current device data sheet to check whether this document supports the device

you are using.

Device data sheets and family reference manual sections are available for

download from the Microchip Worldwide Web site at: http://www.microchip.com

IMPORTANT: The implementation and use of the USB specifications, as well as other

third-party specifications or technologies, may require licensing; including,

but not limited to, USB Implementers Forum, Inc. (also referred to as

USB-IF). The user is fully responsible for investigating and satisfying any

applicable licensing obligations.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

Figure 27-1: PIC32 USB OTG Interface Diagram

Note 1: PB clock is only available on this pin for select EC modes.

2: Pins can be used as digital inputs when USB is not enabled.

3: This bit field is contained in the OSCCON register.

4: This bit field is contained in the OSCTRM register.

5: USB PLL UFIN requirements: 4 MHz ≤ UFIN ≤ 5 MHz.

6: This bit field is contained in the DEVCFG2 register.

7: A 48 MHz clock is required for proper USB operation.

8: Pins can be used as GPIO when the USB OTG module is disabled.

9: Pin is pulled high internally when USB OTG module is enabled.

OSC1

OSC2

Primary Oscillator

8 MHz Typical

FRC

Oscillator

TUN<5:0>(4)

PLL

48 MHz USB Clock(7)

Div x

UPLLEN(6)

(PBOUT)(1)

UFRCEN(3)

(POSC)

FUPLLIDIV(6)

UFIN(5)

Div 2

VUSB

D+(2)

D-(2)

ID(8,9)

VBUS

Transceiver

SIE

VBUSON(8)

Comparators

USB

SRP Charge

SRP Discharge

Registers

and

Control

Interface

Transceiver Power 3.3V

To Clock Generator for Core and Peripherals

Sleep or Idle

Sleep

USBEN

USB Suspend

CPU Clock Not POSC

USB OTG Module

Voltage

System

RAM

USB Suspend

Full-Speed Pull-up

Host Pull-down

Low-Speed Pull-up

Host Pull-down

ID Pull-up

Bus

Master

24xPLL

PIC32 Family Reference Manual

27.2 CONTROL REGISTERS

The USB OTG module includes the following Special Function Registers (SFRs):

•U1OTGIR: USB OTG Interrupt Status Register

This register records changes on the ID, data and VBUS pins, enabling software to determine

which event caused an interrupt. The interrupt bits are cleared by writing a ‘1’ to the corresponding

interrupt.

•U1OTGIE: USB OTG Interrupt Enable Register

This register enables the corresponding interrupt status bits defined in the U1OTGIR register

to generate an interrupt.

•U1OTGSTAT: USB OTG Status Register

This register provides access to the status of the VBUS voltage comparators and the

debounced status of the ID pin.

•U1OTGCON: USB OTG Control Register

This register controls the operation of the VBUS pin, and the pull-up and pull-down resistors.

•U1PWRC: USB Power Control Register

This register controls the power-saving modes, as well as the module enable/disable

control.

•U1IR: USB Interrupt Register

This register contains information on pending interrupts. Once an interrupt bit is set, it can

be cleared by writing a ‘1’ to the corresponding bit.

•U1IE: USB Interrupt Enable Register(1)

The values in this register provide gating of the various interrupt signals onto the USB inter-

rupt signal. These values do not interact with the USB OTG module. Setting any of these

bits enables the corresponding interrupt source in the U1IR register.

•U1EIR: USB Error Interrupt Status Register

This register contains information on pending error interrupt values. Once an interrupt bit is

set, it can be cleared by writing a ‘1’ to the corresponding bit.

•U1EIE: USB Error Interrupt Enable Register(1)

The values in this register provide gating of the various interrupt signals onto the USB

interrupt signal. These values do not interact with the USB OTG module. Setting any of

these bits enables the respective interrupt source in the U1EIR register, if the UERRIE bit

(U1IE<1>) is also set.

•U1STAT: USB Status Register(1)

U1STAT is a 16-deep First In, First Out register (FIFO). It is read-only by the CPU and

read/write by the USB OTG module. U1STAT is only valid when the TRNIF bit (U1IR<3>) is

set.

•U1CON: USB Control Register

This register provides miscellaneous control and information about the module.

•U1ADDR: USB Address Register

U1ADDR is a read/write register from the CPU side and read-only from the USB OTG mod-

ule side. Although the register values affect the settings of the USB OTG module, the

content of the registers does not change during access.

In Device mode, this address defines the USB device address as assigned by the host dur-

ing the SETUP phase. The firmware writes the address in response to the SETUP request.

The address is automatically reset when a USB bus Reset is detected. In Host mode, the

module transmits the address provided in this register with the corresponding token packet.

This allows the USB OTG module to uniquely address the connected device.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

•U1FRML: USB Frame Number Low Register and U1FRMH: USB Frame Number High

U1FRML and U1FRMH are read-only registers. The frame number is formed by concatenat-

ing the two 8-bit registers. The high-order byte is in the U1FRMH register, and the low-order

byte is in U1FRML.

•U1TOK: USB Token Register

U1TOK is a read/write register required when the module operates as a host. It is used to

specify the token type, PID<3:0> (Packet ID), and the endpoint, EP<3:0>, being addressed

by the host processor. Writing to this register triggers a host transaction.

•U1SOF: USB SOF Threshold Register

U1SOF is a read/write register that contains the count bits of the Start of Frame (SOF)

threshold value, and are used in Host mode only.

To prevent colliding a packet data with the SOF token that is sent every 1 ms, the USB OTG

module will not send any new transactions within the last U1SOF byte times. The USB OTG

module will complete any transactions that are in progress. In Host mode, the SOF interrupt

occurs when this threshold is reached, not when the SOF occurs. In Device mode, the inter-

rupt occurs when a SOF is received. Transactions started within the SOF threshold are held

by the USB OTG module until after the SOF token is sent.

•U1BDTP1: USB BDT Register, U1BDTP2: USB BDT PAGE 2 Register, and U1BDTP3:

USB BDT PAGE 3 Register

These registers are read/write registers that define the upper 23 bits of the 32-bit base

address of the Buffer Descriptor Table (BDT) in the system memory. The BDT is forced to

be 512 byte-aligned. This register allows relocation of the BDT in real time.

•U1CNFG1: USB Configuration 1 Register

U1CNFG1 is a read/write register that controls the Debug and Idle behavior of the module.

The register must be preprogrammed prior to enabling the module.

•U1EP0-U1EP15: USB Endpoint Control Registers

These registers control the behavior of the corresponding endpoint.

27.2.1 Associated Registers

Refer to Section 6. “Oscillators” (DS61112) for information on the register bits used to enable

the USB PLL and/or USB FRC clock sources.

Refer to Section 8. “Interrupts” (DS61108) for information on the register bits used to enable

and identify the USB OTG module interrupts.

Refer to Section 32. “Configuration” (DS61124) for information on the configuration bits used

to enable the USB PLL and set the appropriate divisor. This section also describes the bits that

can be used to reclaim the USBID and VBUSON pins if the USB OTG module will only be operated

in a mode that does not require them.

27.2.2 Clearing USB OTG Interrupts

Unlike other device-level interrupts, the USB OTG interrupt status flags are not freely writable in

software. All USB OTG flag bits are implemented as hardware-set-only bits. These bits can only

be cleared in software by writing a ‘1’ to their locations. Writing a ‘0’ to a flag bit has no effect.

Note: Throughout this section, a bit that can only be cleared by writing a ‘1’ to its location

is referred to as “Write ‘ ’ to clear bit”. In register 1descriptions, this function is

indicated by the descriptor ‘K’.

PIC32 Family Reference Manual

27.2.3 Register Summary

All USB OTG registers are summarized in Table 27-1.

Table 27-1: USB OTG Register Summary(1)

Name

Bit

Range

Bit

31/23/15/7

Bit

30/22/14/6

Bit

29/21/13/5

Bit

28/20/12/4

Bit

27/19/11/3

Bit

26/18/10/2

Bit

25/17/9/1

Bit

24/16/8/0

U1OTGIR 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 IDIF T1MSECIF LSTATEIF ACTVIF SESVDIF SESENDIF — VBUSVDIF

U1OTGIE 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 IDIE T1MSECIE LSTATEIE ACTVIE SESVDIE SESENDIE — VBUSVDIE

U1OTGSTAT 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 ID — LSTATE — SESVD SESEND — VBUSVD

U1OTGCON 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 DPPULUP DMPULUP DPPULDWN DMPULDWN VBUSON OTGEN VBUSCHG VBUSDIS

U1PWRC 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 UACTPND — — USLPGRD USBBUSY(2) — USUS-

PEND

USBPWR

U1IR 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 STALLIF ATTACHIF RESUMEIF IDLEIF TRNIF SOFIF UERRIF URSTIF

DETACHIF

U1IE 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 STALLIE ATTACHIE RESUMEIE IDLEIE TRNIE SOFIE UERRIE URSTIE

DETACHIE

U1EIR 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 BTSEF BMXEF DMAEF BTOEF DFN8EF CRC16EF CRC5EF PIDEF

EOFEF

U1EIE 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 BTSEE BMXEE DMAEE BTOEE DFN8EE CRC16EE CRC5EE PIDEE

EOFEE

U1STAT 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 ENDPT<3:0> DIR PPBI — —

Legend: — = unimplemented, read as ‘0’. Address offset values are shown in hexadecimal.

Note 1: Not all registers may have associated SET, CLR, INV registers. Refer to the specific device data sheet for details.

2: This bit is not available on all devices. Refer to the specific device data sheet for details.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U1CON 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 JSTATE SE0 PKTDIS USBRST HOSTEN RESUME PPBRST USBEN

TOKBUSY SOFEN

U1ADDR 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 LSPDEN DEVADDR<6:0>

U1BDTP1 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 BDTPTRL<15:9> —

U1FRML 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 FRML<7:0>

U1FRMH 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — — — FRMH<2:0>

U1TOK 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 PID<3:0> EP<3:0>

U1SOF 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 CNT<7:0>

U1BDTP2 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 BDTPTRH<23:16>

U1BDTP3 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 BDTPTRU<31:24>

U1CNFG1 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 UTEYE UOEMON USBFRZ USBSIDL — — — UASUSPND(2)

U1EP0 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 LSPD RETRYDIS — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP1 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

Table 27-1: USB OTG Register Summary(1) (Continued)

Name

Bit

Range

Bit

31/23/15/7

Bit

30/22/14/6

Bit

29/21/13/5

Bit

28/20/12/4

Bit

27/19/11/3

Bit

26/18/10/2

Bit

25/17/9/1

Bit

24/16/8/0

Legend: — = unimplemented, read as ‘0’. Address offset values are shown in hexadecimal.

Note 1: Not all registers may have associated SET, CLR, INV registers. Refer to the specific device data sheet for details.

2: This bit is not available on all devices. Refer to the specific device data sheet for details.

PIC32 Family Reference Manual

U1EP2 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP3 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP4 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP5 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP6 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP7 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP8 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP9 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP10 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP11 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP12 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP13 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

Table 27-1: USB OTG Register Summary(1) (Continued)

Name

Bit

Range

Bit

31/23/15/7

Bit

30/22/14/6

Bit

29/21/13/5

Bit

28/20/12/4

Bit

27/19/11/3

Bit

26/18/10/2

Bit

25/17/9/1

Bit

24/16/8/0

Legend: — = unimplemented, read as ‘0’. Address offset values are shown in hexadecimal.

Note 1: Not all registers may have associated SET, CLR, INV registers. Refer to the specific device data sheet for details.

2: This bit is not available on all devices. Refer to the specific device data sheet for details.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U1EP14 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

U1EP15 31:24 — — — — — — — —

23:16 — — — — — — — —

15:8 — — — — — — — —

7:0 — — — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

Table 27-1: USB OTG Register Summary(1) (Continued)

Name

Bit

Range

Bit

31/23/15/7

Bit

30/22/14/6

Bit

29/21/13/5

Bit

28/20/12/4

Bit

27/19/11/3

Bit

26/18/10/2

Bit

25/17/9/1

Bit

24/16/8/0

Legend: — = unimplemented, read as ‘0’. Address offset values are shown in hexadecimal.

Note 1: Not all registers may have associated SET, CLR, INV registers. Refer to the specific device data sheet for details.

2: This bit is not available on all devices. Refer to the specific device data sheet for details.

PIC32 Family Reference Manual

27.2.4 Register Definitions

This section provides a detailed description of each USB OTG register.

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 15 bit 8

R/K-0 R/K-0 R/K-0 R/K-0 R/K-0 R/K-0 U-0 R/K-0

IDIF T1MSECIF LSTATEIF ACTVIF SESVDIF SESENDIF — VBUSVDIF

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit K = Write ‘1’ to clear -n = Bit Value at POR: (‘0’, ‘1’, x = unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 IDIF: ID State Change Indicator bit

Write a ‘1’ to this bit to clear the interrupt.

1 = Change in ID state detected

0 = No change in ID state detected

bit 6 T1MSECIF: 1 Millisecond Timer bit

Write a ‘1’ to this bit to clear the interrupt.

1 = 1 millisecond timer has expired

0 = 1 millisecond timer has not expired

bit 5 LSTATEIF: Line State Stable Indicator bit

Write a ‘1’ to this bit to clear the interrupt.

1 = USB line state has been stable for 1 ms, but different from last time

0 = USB line state has not been stable for 1 ms

bit 4 ACTVIF: Bus Activity Indicator bit

Write a ‘1’ to this bit to clear the interrupt.

1 = Activity on the D+, D-, ID or VBUS pins has caused the device to wake-up

0 = Activity has not been detected

bit 3 SESVDIF: Session Valid Change Indicator bit

Write a ‘1’ to this bit to clear the interrupt.

1 = VBUS voltage has dropped below the session end level

0 = VBUS voltage has not dropped below the session end level

bit 2 SESENDIF: B-Device VBUS Change Indicator bit

Write a ‘1’ to this bit to clear the interrupt.

1 = A change on the session end input was detected

0 = No change on the session end input was detected

bit 1 Unimplemented: Read as ‘0’

bit 0 VBUSVDIF: A-Device VBUS Change Indicator bit

Write a ‘1’ to this bit to clear the interrupt.

1 = Change on the session valid input detected

0 = No change on the session valid input detected

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 U-0 R/W-0

IDIE T1MSECIE LSTATEIE ACTVIE SESVDIE SESENDIE — VBUSVDIE

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 IDIE: ID Interrupt Enable bit

1 = ID interrupt enabled

0 = ID interrupt disabled

bit 6 T1MSECIE: 1 Millisecond Timer Interrupt Enable bit

1 = 1 millisecond timer interrupt enabled

0 = 1 millisecond timer interrupt disabled

bit 5 LSTATEIE: Line State Interrupt Enable bit

1 = Line state interrupt enabled

0 = Line state interrupt disabled

bit 4 ACTVIE: Bus Activity Interrupt Enable bit

1 = ACTIVITY interrupt enabled

0 = ACTIVITY interrupt disabled

bit 3 SESVDIE: Session Valid Interrupt Enable bit

1 = Session valid interrupt enabled

0 = Session valid interrupt disabled

bit 2 SESENDIE: B-Session End Interrupt Enable bit

1 = B-session end interrupt enabled

0 = B-session end interrupt disabled

bit 1 Unimplemented: Read as ‘0’

bit 0 VBUSVDIE: A-VBUS Valid Interrupt Enable bit

1 = A-VBUS valid interrupt enabled

0 = A-VBUS valid interrupt disabled

PIC32 Family Reference Manual

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 15 bit 8

R-0 U-0 R-0 U-0 R-0 R-0 U-0 R-0

ID — LSTATE — SESVD SESEND — VBUSVD

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 ID: ID Pin State Indicator bit

1 = No cable is attached or a type B cable has been plugged into the USB receptacle

0 = A “type A” OTG cable has been plugged into the USB receptacle

bit 6 Unimplemented: Read as ‘0’

bit 5 LSTATE: Line State Stable Indicator bit

1 = USB line state (U1CON<SE0> and U1CON<JSTATE>) has been stable for the previous 1 ms

0 = USB line state (U1CON<SE0> and U1CON<JSTATE>) has not been stable for the previous 1 ms

bit 4 Unimplemented: Read as ‘0’

bit 3 SESVD: Session Valid Indicator bit

1 = VBUS voltage is above Session Valid on the A or B device

0 = VBUS voltage is below Session Valid on the A or B device

bit 2 SESEND: B-Session End Indicator bit

1 = VBUS voltage is below Session Valid on the B device

0 = VBUS voltage is above Session Valid on the B device

bit 1 Unimplemented: Read as ‘0’

bit 0 VBUSVD: A-VBUS Valid Indicator bit

1 = VBUS voltage is above Session Valid on the A device

0 = VBUS voltage is below Session Valid on the A device

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

DPPULUP DMPULUP DPPULDWN DMPULDWN VBUSON OTGEN VBUSCHG VBUSDIS

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 DPPULUP: D+ Pull-Up Enable bit

1 = D+ data line pull-up resistor is enabled

0 = D+ data line pull-up resistor is disabled

bit 6 DMPULUP: D- Pull-Up Enable bit

1 = D- data line pull-up resistor is enabled

0 = D- data line pull-up resistor is disabled

bit 5 DPPULDWN: D+ Pull-Down Enable bit

1 = D+ data line pull-down resistor is enabled

0 = D+ data line pull-down resistor is disabled

bit 4 DMPULDWN: D- Pull-Down Enable bit

1 = D- data line pull-down resistor is enabled

0 = D- data line pull-down resistor is disabled

bit 3 VBUSON: VBUS Power-on bit

1 = VBUS line is powered

0 = VBUS line is not powered

bit 2 OTGEN: OTG Functionality Enable bit

1 = DPPULUP, DMPULUP, DPPULDWN and DMPULDWN bits are under software control

0 = DPPULUP, DMPULUP, DPPULDWN and DMPULDWN bits are under USB hardware control

bit 1 VBUSCHG: VBUS Charge Enable bit

1 = VBUS line is charged through a pull-up resistor

0 = VBUS line is not charged through a resistor

bit 0 VBUSDIS: VBUS Discharge Enable bit

1 = VBUS line is discharged through a pull-down resistor

0 = VBUS line is not discharged through a resistor

PIC32 Family Reference Manual

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 15 bit 8

HS, HC-x U-0 U-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0

UACTPND — — USLPGRD USBBUSY(1) — USUSPEND USBPWR

bit 7 bit 0

Legend:

HC = Cleared by hardware HS = Set by hardware

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 UACTPND: USB Activity Pending bit

1 = USB bus activity has been detected; but an interrupt is pending, it has not been generated yet

0 = An interrupt is not pending

bit 6-5 Unimplemented: Read as ‘0’

bit 4 USLPGRD: USB Sleep Entry Guard bit

1 = Sleep entry is blocked if USB bus activity is detected or if a notification is pending

0 = USB OTG module does not block Sleep entry

bit 3 USBBUSY: USB OTG module Busy bit(1)

1 = USB OTG module is active or disabled, but not ready to be enabled

0 = USB OTG module is not active and is ready to be enabled

Note : When USBPWR = 0 1 and USBBUSY = , status from all other registers is invalid and writes

to all USB OTG module registers produce undefined results.

bit 2 Unimplemented: Read as ‘0’

bit 1 USUSPEND: USB Suspend Mode bit

1 = USB OTG module is placed in Suspend mode

(The 48 MHz USB clock will be gated off. The transceiver is placed in a low-power state.)

0 = USB OTG module operates normally

bit 0 USBPWR: USB Operation Enable bit

1 = USB OTG module is turned on

0 = USB OTG module is disabled

(Outputs held inactive, device pins not used by USB, analog features are shut down to reduce

power consumption.)

Note 1: This bit is not available on all devices. Refer to the specific device data sheet for details.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R/K-0 R/K-0 R/K-0 R/K-0 R/K-0 R/K-0 R/K-0 R/K-0

STALLIF ATTACHIF(1) RESUMEIF(2) IDLEIF TRNIF(3) SOFIF UERRIF(4) URSTIF(5)

DETACHIF(6)

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit K = Write ‘1’ to clear -n = Bit Value at POR: (0, 1, x = unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 STALLIF: STALL Handshake Interrupt bit

Write a ‘1’ to this bit to clear the interrupt.

1 = In Host mode a STALL handshake was received during the handshake phase of the transaction

In Device mode a STALL handshake was transmitted during the handshake phase of the transaction.

0 = STALL handshake has not been sent

bit 6 ATTACHIF: Peripheral Attach Interrupt bit(1)

Write a ‘1’ to this bit to clear the interrupt.

1 = Peripheral attachment was detected by the USB OTG module

0 = Peripheral attachment was not detected

bit 5 RESUMEIF: Resume Interrupt bit

(2)

Write a ‘1’ to this bit to clear the interrupt.

1 = K-State is observed on the D+ or D- pin for 2.5 µs

0 = K-State is not observed

bit 4 IDLEIF: Idle Detect Interrupt bit

Write a ‘1’ to this bit to clear the interrupt.

1 = Idle condition detected (constant Idle state of 3 ms or more)

0 = No Idle condition detected

Note 1: This bit is valid only if the HOSTEN bit is set (see Register 27-11), there is no activity on the USB for

2.5 µs, and the current bus state is not SE0.

2: When not in Suspend mode, this interrupt should be disabled.

3: Clearing this bit will cause the STAT FIFO to advance.

4: Only error conditions enabled through the U1EIE register will set this bit.

5: Device mode.

6: Host mode.

PIC32 Family Reference Manual

bit 3 TRNIF: Token Processing Complete Interrupt bit(3)

Write a ‘1’ to this bit to clear the interrupt.

1 = Processing of current token is complete; a read of the U1STAT register will provide endpoint

information

0 = Processing of current token not complete

bit 2 SOFIF: SOF Token Interrupt bit

Write a ‘1’ to this bit to clear the interrupt.

1 = SOF token received by the peripheral or the SOF threshold reached by the host

0 = SOF token was not received nor threshold reached

bit 1 UERRIF: USB Error Condition Interrupt bit(4)

Write a ‘1’ to this bit to clear the interrupt.

1 = Unmasked error condition has occurred

0 = Unmasked error condition has not occurred

bit 0 URSTIF: USB Reset Interrupt bit (Device mode)(5)

1 = Valid USB Reset has occurred

0 = No USB Reset has occurred

DETACHIF: USB Detach Interrupt bit (Host mode)(6)

1 = Peripheral detachment was detected by the USB OTG module

0 = Peripheral detachment was not detected

Note 1: This bit is valid only if the HOSTEN bit is set (see Register 27-11), there is no activity on the USB for

2.5 µs, and the current bus state is not SE0.

2: When not in Suspend mode, this interrupt should be disabled.

3: Clearing this bit will cause the STAT FIFO to advance.

4: Only error conditions enabled through the U1EIE register will set this bit.

5: Device mode.

6: Host mode.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

STALLIE ATTACHIE RESUMEIE IDLEIE TRNIE SOFIE UERRIE URSTIE(2)

DETACHIE(3)

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 STALLIE: STALL Handshake Interrupt Enable bit

1 = STALL interrupt enabled

0 = STALL interrupt disabled

bit 6 ATTACHIE: ATTACH Interrupt Enable bit

1 = ATTACH interrupt enabled

0 = ATTACH interrupt disabled

bit 5 RESUMEIE: RESUME Interrupt Enable bit

1 = RESUME interrupt enabled

0 = RESUME interrupt disabled

bit 4 IDLEIE: Idle Detect Interrupt Enable bit

1 = Idle interrupt enabled

0 = Idle interrupt disabled

bit 3 TRNIE: Token Processing Complete Interrupt Enable bit

1 = TRNIF interrupt enabled

0 = TRNIF interrupt disabled

bit 2 SOFIE: SOF Token Interrupt Enable bit

1 = SOFIF interrupt enabled

0 = SOFIF interrupt disabled

bit 1 UERRIE: USB Error Interrupt Enable bit

1 = USB Error interrupt enabled

0 = USB Error interrupt disabled

Note 1: For an interrupt to propagate to the USBIF bit (IFS1<25>), the UERRIE bit (U1IE<1>) must be set.

2: Device mode.

3: Host mode.

PIC32 Family Reference Manual

bit 0 URSTIE: USB Reset Interrupt Enable bit(2)

1 = URSTIF interrupt enabled

0 = URSTIF interrupt disabled

DETACHIE: USB Detach Interrupt Enable bit(3)

1 = DATTCHIF interrupt enabled

0 = DATTCHIF interrupt disabled

(1) (Continued)

Note 1: For an interrupt to propagate to the USBIF bit (IFS1<25>), the UERRIE bit (U1IE<1>) must be set.

2: Device mode.

3: Host mode.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R/K-0 R/K-0 R/K-0 R/K-0 R/K-0 R/K-0 R/K-0 R/K-0

BTSEF BMXEF DMAEF(1) BTOEF(2) DFN8EF CRC16EF CRC5EF(3,4)

PIDEF

EOFEF(5)

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit K = Write ‘1’ to clear -n = Bit Value at POR: (‘0’, ‘1’, x = unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 BTSEF: Bit Stuff Error Flag bit

Write a ‘1’ to this bit to clear the interrupt.

1 = Packet rejected due to bit stuff error

0 = Packet accepted

bit 6 BMXEF: Bus Matrix Error Flag bit

Write a ‘1’ to this bit to clear the interrupt.

1 = The base address, of the BDT, or the address of an individual buffer pointed to by a BDT entry,

is invalid.

0 = No address error

bit 5 DMAEF: DMA Error Flag bit(1)

Write a ‘1’ to this bit to clear the interrupt.

1 = USB DMA error condition detected

0 = No DMA error

Note 1: This type of error occurs when the module’s request for the DMA bus is not granted in time to service the

module’s demand for memory, resulting in an overflow or underflow condition, and/or the allocated buffer

size is not sufficient to store the received data packet causing it to be truncated.

2: This type of error occurs when more than 16-bit-times of Idle from the previous End-of-Packet (EOP)

has elapsed.

3: This type of error occurs when the module is transmitting or receiving data and the SOF counter has

reached zero.

4: Device mode.

5: Host mode.

PIC32 Family Reference Manual

bit 4 BTOEF: Bus Turnaround Time-Out Error Flag bit(2)

Write a ‘1’ to this bit to clear the interrupt.

1 = Bus turnaround time-out has occurred

0 = No bus turnaround time-out

bit 3 DFN8EF: Data Field Size Error Flag bit

Write a ‘1’ to this bit to clear the interrupt.

1 = Data field received is not an integral number of bytes

0 = Data field received is an integral number of bytes

bit 2 CRC16EF: CRC16 Failure Flag bit

Write a ‘1’ to this bit to clear the interrupt.

1 = Data packet rejected due to CRC16 error

0 = Data packet accepted

bit 1 CRC5EF: CRC5 Host Error Flag bit(3,4)

Write a ‘1’ to this bit to clear the interrupt.

1 = Token packet rejected due to CRC5 error

0 = Token packet accepted

EOFEF: EOF Error Flag bit(5)

1 = EOF error condition detected

0 = No EOF error condition

bit 0 PIDEF: PID Check Failure Flag bit

1 = PID check failed

0 = PID check passed

Note 1: This type of error occurs when the module’s request for the DMA bus is not granted in time to service the

module’s demand for memory, resulting in an overflow or underflow condition, and/or the allocated buffer

size is not sufficient to store the received data packet causing it to be truncated.

2: This type of error occurs when more than 16-bit-times of Idle from the previous End-of-Packet (EOP)

has elapsed.

3: This type of error occurs when the module is transmitting or receiving data and the SOF counter has

reached zero.

4: Device mode.

5: Host mode.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

BTSEE BMXEE DMAEE BTOEE DFN8EE CRC16EE CRC5EE(2)

PIDEE

EOFEE(3)

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 BTSEE: Bit Stuff Error Interrupt Enable bit

1 = BTSEF interrupt enabled

0 = BTSEF interrupt disabled

bit 6 BMXEE: Bus Matrix Error Interrupt Enable bit

1 = BMXEF interrupt enabled

0 = BMXEF interrupt disabled

bit 5 DMAEE: DMA Error Interrupt Enable bit

1 = DMAEF interrupt enabled

0 = DMAEF interrupt disabled

bit 4 BTOEE: Bus Turnaround Time-out Error Interrupt Enable bit

1 = BTOEF interrupt enabled

0 = BTOEF interrupt disabled

bit 3 DFN8EE: Data Field Size Error Interrupt Enable bit

1 = DFN8EF interrupt enabled

0 = DFN8EF interrupt disabled

bit 2 CRC16EE: CRC16 Failure Interrupt Enable bit

1 = CRC16EF interrupt enabled

0 = CRC16EF interrupt disabled

Note 1: For an interrupt to propagate USBIF bit (IFS1<25>), the UERRIE bit (U1IE<1>) must be set.

2: Device mode.

3: Host mode.

PIC32 Family Reference Manual

bit 1 CRC5EE: CRC5 Host Error Interrupt Enable bit(2)

1 = CRC5EF interrupt enabled

0 = CRC5EF interrupt disabled

EOFEE: EOF Error Interrupt Enable bit(3)

1 = EOF interrupt enabled

0 = EOF interrupt disabled

bit 0 PIDEE: PID Check Failure Interrupt Enable bit

1 = PIDEF interrupt enabled

0 = PIDEF interrupt disabled

Note 1: For an interrupt to propagate USBIF bit (IFS1<25>), the UERRIE bit (U1IE<1>) must be set.

2: Device mode.

3: Host mode.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R-x R-x R-x R-x R-x R-x U-0 U-0

ENDPT<3:0> DIR PPBI — —

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7-4 ENDPT<3:0>: Encoded Number of Last Endpoint Activity bits

(Represents the number of the BDT, updated by the last USB transfer.)

1111 = Endpoint 15

1110 = Endpoint 14

•

0001 = Endpoint 1

0000 = Endpoint 0

bit 3 DIR: Last BD Direction Indicator bit

1 = Last transaction was a transmit transfer (TX)

0 = Last transaction was a receive transfer (RX)

bit 2 PPBI: Ping-Pong BD Pointer Indicator bit

1 = The last transaction was to the ODD BD bank

0 = The last transaction was to the EVEN BD bank

bit 1-0 Unimplemented: Read as ‘0’

Note 1: The U1STAT register is a window into a 4 byte FIFO maintained by the USB OTG module. U1STAT value

is only valid when the TRNIF bit (U1IR<3>) is active. Clearing the TRNIF bit (U1IR<3>) advances the

FIFO. Data in register is invalid when the TRNIF bit (U1IR<3>) = 0.

PIC32 Family Reference Manual

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R-x R-x R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

JSTATE SE0 PKTDIS(4)

USBRST HOSTEN(2) RESUME(3) PPBRST USBEN(4)

TOKBUSY(1,5) SOFEN(5)

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 JSTATE: Live Differential Receiver JSTATE flag bit

1 = JSTATE detected on the USB

0 = No JSTATE detected

bit 6 SE0: Live Single-Ended Zero flag bit

1 = Single Ended Zero detected on the USB

0 = No Single Ended Zero detected

bit 5 PKTDIS: Packet Transfer Disable bit(4)

1 = Token and packet processing disabled (set upon SETUP token received)

0 = Token and packet processing enabled

TOKBUSY: Token Busy Indicator bit(1,5)

1 = Token being executed by the USB OTG module

0 = No token being executed

bit 4 USBRST: Module Reset bit(5)

1 = USB reset generated

0 = USB reset terminated

Note 1: Software is required to check this bit before issuing another token command to the U1TOK register, see

2: All host control logic is reset any time that the value of this bit is toggled.

3: Software must set RESUME for 10 ms if the part is a function, or for 25 ms if the part is a host, and then

clear it to enable remote wake-up. In Host mode, the USB OTG module will append a low-speed EOP to

the RESUME signaling when this bit is cleared.

4: Device mode.

5: Host mode.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

bit 3 HOSTEN: Host Mode Enable bit(2)

1 = USB host capability enabled

0 = USB host capability disabled

bit 2 RESUME: RESUME Signaling Enable bit(3)

1 = RESUME signaling activated

0 = RESUME signaling disabled

bit 1 PPBRST: Ping-Pong Buffers Reset bit

1 = Reset all Even/Odd buffer pointers to the EVEN BD banks

0 = Even/Odd buffer pointers not being Reset

bit 0 USBEN: USB OTG Module Enable bit(4)

1 = USB OTG module and supporting circuitry enabled

0 = USB OTG module and supporting circuitry disabled

SOFEN: SOF Enable bit(5)

1 = SOF token sent every 1 ms

0 = SOF token disabled

Note 1: Software is required to check this bit before issuing another token command to the U1TOK register, see

2: All host control logic is reset any time that the value of this bit is toggled.

3: Software must set RESUME for 10 ms if the part is a function, or for 25 ms if the part is a host, and then

clear it to enable remote wake-up. In Host mode, the USB OTG module will append a low-speed EOP to

the RESUME signaling when this bit is cleared.

4: Device mode.

5: Host mode.

PIC32 Family Reference Manual

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

LSPDEN DEVADDR<6:0>

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 LSPDEN: Low-Speed Enable Indicator bit

1 = Next token command to be executed at low-speed

0 = Next token command to be executed at full-speed

bit 6-0 DEVADDR<6:0>: 7-bit USB Device Address bits

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R-0 R-0 R-0 R-0 R-0 R-0 R-0 R-0

FRML<7:0>

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7-0 FRML<7:0>: The 11-bit Frame Number Lower bits

The register bits are updated with the current frame number whenever a SOF TOKEN is received.

PIC32 Family Reference Manual

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 15 bit 8

U-0 U-0 U-0 U-0 U-0 R-0 R-0 R-0

— — — — — FRMH<2:0>

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-3 Unimplemented: Read as ‘0’

bit 2-0 FRMH<2:0>: The Upper 3 bits of the Frame Number bits

The register bits are updated with the current frame number whenever a SOF TOKEN is received.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

PID<3:0>(1) EP<3:0>

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7-4 PID<3:0>: Token Type Indicator bits(1)

0001 = OUT (TX) token type transaction

1001 = IN (RX) token type transaction

1101 = SETUP (TX) token type transaction

Note: All other values are reserved and must not be used.

bit 3-0 EP<3:0>: Token Command Endpoint Address bits

The four bit value must specify a valid endpoint.

Note 1: All other values are reserved and must not be used.

PIC32 Family Reference Manual

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

CNT<7:0>

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7-0 CNT<7:0>: SOF Threshold Value bits

Typical values of the threshold are:

0100 1010 = 64-byte packet

0010 1010 = 32-byte packet

0001 1010 = 16-byte packet

0001 0010 = 8-byte packet

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 U-0

BDTPTRL<15:9> —

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7-1 BDTPTRL<15:9>: BDT Base Address Low bits

This 7-bit value provides address bits 15 through 9 of the BDT base address, which defines the BDT’s

starting location in the system memory.

The 32-bit BDT base address is 512 byte aligned.

bit 0 Unimplemented: Read as ‘0’

PIC32 Family Reference Manual

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

————————

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

BDTPTRH<23:16>

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7-0 BDTPTRH<23:16>: BDT Base Address High bits

This 8-bit value provides address bits 23 through 16 of the BDT base address, which defines the BDT’s

starting location in the system memory.

The 32-bit BDT base address is 512 byte aligned.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

BDTPTRU<31:24>

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7-0 BDTPTRU<31:24>: BDT Base Address Upper bits

This 8-bit value provides address bits 31 through 24 of the BDT base address, which defines the BDT’s

starting location in the system memory.

The 32-bit BDT base address is 512 byte aligned.

PIC32 Family Reference Manual

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

——————— —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

——————— —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

——————— —

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 U-0 U-0 U-0 R/W-0

UTEYE UOEMON USBFRZ USBSIDL — — — UASUSPND(1)

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 UTEYE: USB Eye-Pattern Test Enable bit

1 = Eye-Pattern Test enabled

0 = Eye-Pattern Test disabled

bit 6 UOEMON: USB OE Monitor Enable bit

1 = OE signal active; it indicates intervals during which the D+/D- lines are driving

0 = OE signal inactive

bit 5 USBFRZ: Freeze in Debug Mode bit

1 = When emulator is in Debug mode, module freezes operation

0 = When emulator is in Debug mode, module continues operation

bit 4 USBSIDL: Stop in Idle Mode bit

1 = Discontinue module operation when device enters Idle mode

0 = Continue module operation in Idle mode

bit 3-1 Unimplemented: Read as ‘0’

bit 0 UASUSPND: Automatic Suspend Enable bit(1)

1 = USB OTG module automatically suspends upon entry to Sleep mode. See the USUSPEND bit

(U1PWRC<1>) in Register 27-5.

0 = USB OTG module does not automatically suspend upon entry to Sleep mode. Software must use

the USUSPEND bit (U1PWRC<1>) to suspend the module, including the USB 48 MHz clock

Note 1: This bit is not available on all devices. Refer to the specific device data sheet for details.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 31 bit 24

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 23 bit 16

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

LSPD RETRYDIS — EPCONDIS EPRXEN EPTXEN EPSTALL EPHSHK

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit P = Programmable bit r = Reserved bit

U = Unimplemented bit -n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-8 Unimplemented: Read as ‘0’

bit 7 LSPD: Low-Speed Direct Connection Enable bit (Host mode and U1EP0 only)

1 = Direct connection to a low-speed device enabled

0 = Direct connection to a low-speed device disabled; hub required with PRE_PID

bit 6 RETRYDIS: Retry Disable bit (Host mode and U1EP0 only)

1 = Retry NAK’d transactions disabled

0 = Retry NAK’d transactions enabled; retry done in hardware

bit 5 Unimplemented: Read as ‘0’

bit 4 EPCONDIS: Bidirectional Endpoint Control bit

If EPTXEN = 1 1 and EPRXEN = :

1 = Disable Endpoint n from Control transfers; only TX and RX transfers allowed

0 = Enable Endpoint n for Control (SETUP) transfers; TX and RX transfers also allowed

Otherwise, this bit is ignored.

bit 3 EPRXEN: Endpoint Receive Enable bit

1 = Endpoint n receive enabled

0 = Endpoint n receive disabled

bit 2 EPTXEN: Endpoint Transmit Enable bit

1 = Endpoint n transmit enabled

0 = Endpoint n transmit disabled

bit 1 EPSTALL: Endpoint Stall Status bit

1 = Endpoint n was stalled

0 = Endpoint n was not stalled

bit 0 EPHSHK: Endpoint Handshake Enable bit

1 = Endpoint Handshake enabled

0 = Endpoint Handshake disabled (typically used for isochronous endpoints)

PIC32 Family Reference Manual

27.3 OPERATION

This section contains a brief overview of USB operation, followed by USB OTG module

implementation specifics, and module initialization requirements.

27.3.1 USB 2.0 Operation Overview

USB is an asynchronous serial interface with a tiered star configuration. USB is implemented as

a master/slave configuration. On a given bus, there can be multiple (up to 127) slaves (devices),

but there is only one master (host).

27.3.2 Modes of Operation

The following USB implementation modes are described in this overview:

• Host mode

- USB Standard Host mode: The USB implementation that is typically used for a

personal computer

- Embedded Host mode: The USB implementation that is typically used for a

microcontroller

• Device mode – the USB implementation that is typically used for a peripheral such as a

thumb drive, keyboard or mouse

• OTG Dual Role mode – the USB implementation in which an application may dynamically

switch its role as either host or device

27.3.2.1 HOST MODE

The host is the master in a USB system and is responsible for identifying all devices connected

to it (enumeration), initiating all transfers, allocating bus bandwidth and supplying power to any

bus-powered USB devices connected directly to it.

27.3.2.1.1 USB Standard Host

In USB Standard Host mode, the following features and requirements are relevant:

• Large variety of devices are supported

• Supports all USB transfer types

• USB hubs are supported (allows connection of multiple devices simultaneously)

• Device drivers can be updated to support new devices

• Type ‘A’ receptacle is used for each port

• Each port must be able to deliver a minimum of 100 mA for a configured or unconfigured

device, and optionally, up to 500 mA for a configured device

• Full-speed and low-speed protocols must be supported (high-speed can be supported)

27.3.2.1.2 Embedded Host

In Embedded Host mode, the following features and requirements are relevant:

• Only supports a specific list of devices, referred to as a Targeted Peripheral List (TPL)

• Only required to support those transfer types that are required by devices in the TPL

• USB hub support is optional

• Device drivers are not required to be updatable

• Type ‘A’ receptacle is used for each port

• Only those speeds required by devices in the TPL must be supported

• Each port must be able to deliver a minimum of 100 mA for a configured or unconfigured

device, and optionally, up to 500 mA for a configured device

Note: A good understanding of USB can be gained from documents that are available on

the USB implementers web site. In particular, refer to “Universal Serial Bus

Specification, Revision 2.0” (http://www.usb.org/developers/docs).

Note: High-speed mode is not supported by the USB OTG module.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

27.3.2.2 DEVICE MODE

USB devices accept commands and data from the host and respond to requests for data. USB

devices perform peripheral functions, e.g., a mouse or other I/O, or data storage.

The following characteristics generally describe a USB device:

• Functionality may be class-specific or vendor-specific

• Draws 100 mA or less from the bus before configuration

• Can draw up to 500 mA from the bus after successful negotiation with the host

• Can support low-speed, full-speed, or high-speed protocol (high-speed support requires

implementation of full-speed protocol to enumerate)

• Supports control and data transfers as required for implementation

• Optionally supports Session Request Protocol (SRP)

• Can be bus-powered or self-powered

27.3.2.3 OTG DUAL ROLE MODE

An OTG dual role device supports both USB host and device functionality. OTG dual role devices

use a micro-AB receptacle. This allows a micro-A or a micro-B plug to be attached. Both the

micro-A and micro-B plugs have an additional pin, the ID pin, to signify which plug type was con-

nected. The plug type connected to the receptacle determines the default role of the host or

device. An OTG device will perform the role of a host when a micro-A plug is detected. When a

micro-B plug is detected, the role of a USB device is performed.

When an OTG device is directly connected to another OTG device using an OTG cable (micro-A

to micro-B), Host Negotiation Protocol (HNP) can be used to swap the roles of host and device

between the two without disconnecting and reconnecting the cable. To differentiate between the

two OTG devices, the term “A-device” refers to the device connected to the micro-A plug and

“B-device” refers to the device connected to the micro-B plug.

27.3.2.3.1 A-Device, the Default Host

In OTG dual role, operating as a host, the following features and requirements describe an

A-device:

• Supports the devices on the TPL (class support is not allowed)

• Required to support those transaction types that are required by devices in the TPL

• USB hub support is optional

• Device drivers are not required to be updatable

• A single micro-AB receptacle is used

• Full-speed protocol must be supported (high-speed and/or low-speed protocol can be

supported)

• USB port must be able to deliver a minimum of 8 mA for a configured or unconfigured

device, and optionally, up to 500 mA for a configured device

• Supports HNP; the host can switch roles to become a device

• Supports at least one form of SRP

• A-device supplies VBUS power when the bus is powered, even if the roles are swapped

using HNP

PIC32 Family Reference Manual

27.3.2.3.2 B-Device, the Default Device

In OTG dual role, operating as a USB device, the following features and requirements describe

a B-Device:

• Class- or vendor-specific functionality

• Draws 8 mA or less before configuration

• Is typically self-powered, due to low-current requirements, but can draw up to 500 mA after

successful negotiation with the host

• A single micro-AB receptacle is used

• Must support full-speed protocol (support of low-speed and/or high-speed protocol is

optional

• Supports control transfers, and supports data transfers as they are required for

implementation

• Supports both forms of SRP – VBUS pulsing and data-line pulsing

• Supports HNP

• B-device does not supply VBUS power, even if the roles are swapped using HNP

27.3.3 Protocol

USB communication requires the use of specific protocols. The following subsections provide an

overview of communication via USB.

27.3.3.1 BUS TRANSFERS

Communication on the USB bus occurs through transfers between a host and a device. Each

transfer type has unique features. An embedded or OTG host can implement only the control and

the data transfer(s) it will use.

The following four transfer types are possible on the bus:

• Control

Control transfer is used to identify a device during enumeration and to control it during oper-

ation. A percentage of the USB bandwidth is ensured to be available to control transfers. The

data is verified by a cyclic redundancy check (CRC) and reception by the target is verified.

• Interrupt

Interrupt transfer is a scheduled transfer of data in which the host allocates time slots for the

transfers as required by the device’s configuration. This time slot allocation results in the

device being polled in a periodic manner. The data is verified by a CRC and reception by the

target is acknowledged.

• Isochronous

Isochronous transfer is a scheduled transfer of data in which the host allocates time slots for

the transactions as required by the device’s configuration. Reception of the data is not

acknowledged, but the data integrity is verified by the device using a CRC. This transfer type

is typically used for audio and video.

• Bulk

Bulk transfer is used to move large amounts of data where the time of the transaction is not

ensured. Time for this type of transfer is allocated from time that has not been allocated to

the other three transfer types. The data is verified by a CRC and reception is acknowledged.

The following transfer speeds are defined in “Universal Serial Bus Specification, Revision 2.0”:

• 480 Mbps – high-speed

• 12 Mbps – full-speed

• 1.5 Mbps – low-speed

Note: Dual-role devices that do not support full OTG functionality are possible using

multiple USB receptacles; however, there may be special requirements if these

devices are to be made USB-compliant. Refer to the USB IF (implementers forum)

for details.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

The USB OTG module supports full-speed operation in Host and Device modes, and supports

low-speed operation in Host mode.

Information contrasting the timeliness, data integrity, data size and speed of each transfer, or

transaction, type is shown in Table 27-2.

27.3.3.2 BANDWIDTH ALLOCATION

Control transfers, or transactions, are guaranteed to be at least 10% of the available bandwidth

within a given frame. The remainder is available for allocation to Interrupt and Isochronous trans-

fers. Bulk transfers are allocated from any bandwidth not allocated to control, interrupt or isochro-

nous transfers. Bulk transfers are not assured bandwidth. However, in practice, they have the

greatest bandwidth since frames are rarely completely allocated.

27.3.3.3 ENDPOINTS AND USB DESCRIPTORS

All data transferred on the bus is sent or received through endpoints. USB supports devices with

up to 16 endpoints. Each endpoint can have transmit (TX) and/or receive (RX) functionality. Each

endpoint uses one transaction type. Endpoint 0 is the default control transfer endpoint.

27.3.4 Physical Bus Interface

27.3.4.1 BUS SPEED SELECTION

The USB specification defines full-speed operation as 12 Mbps and low-speed operation as 1.5

Mbps. A data line pull-up resistor is used to identify a device as full-speed or low-speed. For

full-speed operation, the D+ line is pulled up; for low-speed operation, the D- line is pulled up.

27.3.4.2 VBUS CONTROL

VBUS is the 5V USB power supplied by the host, or a hub, to operate bus-powered devices. The

need for VBUS BUS control depends on the role of the application. If V power must be enabled and

disabled, the control must be managed by firmware.

The following list describes the VBUS operation:

• Standard host typically supplies power to the bus at all times

• Host may switch off VBUS to save power

• USB device never powers the bus – VBUS pulsing may be supported as part of the SRP

• OTG A-device supplies power to the bus, and typically turns off VBUS to conserve power

• OTG B-device can pulse VBUS for SRP

Table 27-2: Transaction Types (Full-Speed Operation)

Transaction Type Timeliness Ensured Data Integrity Ensured Maximum Packet

Size

Maximum

Throughput(1)

Control Yes Yes 64 0.83 /s

Interrupt Yes Yes 64 1.22 /s

Isochronous Yes No 1023 1.28 /s

Bulk No Yes 64 1.22 /s

Note 1: These numbers reflect the theoretical maximum data throughput, including protocol overhead, on an other-

wise empty bus. The bit stuffing overhead required by the Non-Return to Zero Inverted (NRZI) encoding is

not included in the calculations.

Note: The PIC32 device does not supply the VBUS power. Refer to the specific device data

sheet for VBUS electrical parameters.

PIC32 Family Reference Manual

27.3.5 PIC32 USB OTG Implementation Specifics

This section details how the USB specification requirements are implemented in the PIC32 USB

OTG module.

27.3.5.1 BUS SPEED

The PIC32 USB OTG module supports the following speeds:

• Full-speed operation as a host and a device

• Low-speed operation as a host

27.3.5.2 ENDPOINTS AND DESCRIPTORS

All USB endpoints are implemented as buffers in RAM. The CPU and USB OTG module have

access to the buffers. To arbitrate access to these buffers between the USB OTG module and

CPU, a semaphore flag system is used. Each endpoint can be configured for TX and/or RX, and

each has an ODD and an EVEN buffer, resulting in up to four buffers per endpoint.

Use of the Buffer Descriptor Table (BDT) allows the buffers to be located anywhere in RAM, and

provides status flags and control bits. The BDT contains the address of each endpoint data buf-

fer, as well as information about each buffer (see Figure 27-2 Figure 27-3, and Figure 27-4).

Each BDT entry is called a Buffer Descriptor (BD) and is 8 bytes long. Four descriptor entries are

used for each endpoint. All endpoints, ranging from endpoint 0 to the highest endpoint in use,

must have four descriptor entries. Even if all of the buffers for an endpoint are not used, four

descriptor entries are required for each endpoint.

The USB OTG module calculates a buffer’s location in memory using the BDT Pointer registers.

The base of the BDT is held in registers U1BDTP1 through U1BDTP3. The address of the

desired buffer is found by using the endpoint number, the type (RX/TX) and the ODD/EVEN bit

to index into the BDT. The address held by this entry is the address of the desired data buffer.

See 27.3.5.3 “Buffer Management”.

Each of the 16 endpoints owns two descriptor pairs: two for packets to transmit, and two for pack-

ets received. Each pair manages two buffers, an EVEN and an ODD, requiring a maximum of 64

descriptors (16*2*2).

Having EVEN and ODD buffers for each direction allows the CPU to access data in one buffer

while the USB OTG module transfers data to or from the other buffer. The USB OTG module

alternates between buffers, clearing the UOWN bit in the buffer descriptor automatically when

the transaction for that buffer is complete. The use of alternating buffers maximizes data through-

put by allowing CPU data access in parallel with data transfer. This technique is referred to as

ping-pong buffering. Figure 27-5 illustrates how the endpoints are mapped in the BDT.

27.3.5.2.1 Endpoint Control

Each endpoint is controlled by an Endpoint Control register, U1EPn, that configures the transfer

direction, the handshake, and the stalling properties of the endpoint. The Endpoint Control

27.3.5.2.2 Host Endpoints

The host performs all transactions through a single endpoint (Endpoint 0). All other endpoints

should be disabled and other endpoint buffers are not be used.

27.3.5.2.3 Device Endpoints

Endpoint 0 must be implemented for a USB device to be enumerated and controlled. Devices

typically implement additional endpoints to transfer data.

Note: The contents of the U1BDTP1-U1BDTP3 registers provide the upper 23 bits of the

32-bit address; therefore, the BDT must be aligned to a 512 byte boundary (see

Figure 27-2). This address must be the physical (not virtual) memory address.

Note: In Host mode, Endpoint 0 has additional bits for auto-retry and hub support.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

27.3.5.3 BUFFER MANAGEMENT

The buffers are shared between the CPU and the USB OTG module, and are implemented in

system memory. So, a simple semaphore mechanism is used to distinguish current ownership of

the BD, and associated buffers, in memory. This semaphore mechanism is implemented by the

UOWN bit in each BD.

The USB OTG module clears the UOWN bit automatically when the transaction for that buffer is

complete. When the UOWN bit is clear, the descriptor is owned by the CPU – which may modify

the descriptor and buffer as necessary.

Software must configure the BDT entry for the next transaction, then set the UOWN bit to return

control to the USB OTG module.

A BD is only valid if the corresponding endpoint has been enabled in the U1EPn register. The

BDT is implemented in data memory, and the BDs are not modified when the USB OTG module

is reset. Initialize the BDs prior to enabling them through the U1EPn. At a minimum, the UOWN

bits must be cleared prior to being enabled.

In Host mode, BDT initialization is required before the U1TOK register is written, which triggers

a transfer.

Figure 27-2: BDT Address Generation

BDTBA<22:0> ENDPOINT<3:0> DIR PPBI FIELD

31:9 8:5 4 3 2:0

bit 31-9 BDTBA<22:0>: BDT Base Address bits

The 23-bit value is made up of the contents of the U1BDTP3, U1BDTP2 and U1BDTP1 registers.

bit 8-5 ENDPOINT<3:0>: Transfer Endpoint Number bits

1111 = Endpoint 15

1110 = Endpoint 14

•

0001 = Endpoint 1

0000 = Endpoint 0

bit 4 DIR: Transfer Direction bit

1 = Transmit: SETUP/OUT for host, IN for function

0 = Receive: IN for host, SETUP/OUT for function

bit 3 PPBI: Ping-Pong Pointer bit

1 = ODD buffer

0 = EVEN buffer

bit 2-0 Manipulated by the USB OTG module

Used to access fields within the BD.

PIC32 Family Reference Manual

27.3.5.3.4 Buffer Descriptor Format

The buffer descriptor is used in the following formats:

• Control

• Status

Buffer descriptor control format, in which software writes the descriptor and hands it to hardware,

is shown in Figure 27-3.

Figure 27-3: USB Buffer Descriptor Control Format: Software to Hardware

Address Offset +0

31 26 25 16 15 8 7 6 5 4 3 2 1 0

—BYTE_COUNT<9:0> —

UOWN

DATA0/1

KEEP

NINC

DTS

BSTALL

—

Address Offset +4

31 0

BUFFER_ADDRESS<31:0>(1)

Address Offset +0

bit 31-26 Reserved

bit 25-16 BYTE_COUNT<9:0>: Byte Count bits

Byte count represents the number of bytes to be transmitted or the maximum number of bytes to be

received during a transfer.

bit 15-8 Reserved

bit 7 UOWN: USB Own bit

1 = USB OTG module owns the BD and its corresponding buffer

CPU must not modify the BD or the buffer.

0 = CPU owns the BD and its corresponding buffer

USB OTG module ignores all other fields in the BD.

USBFRZ is writable in Debug Exception mode only, it is forced to ‘ ’ in normal mode.0

Note: This bit can be programmed by either the CPU or the USB OTG module, and it must be initialized

by the user to the desired value prior to enabling the USB endpoint.

bit 6 DATA0/1: Data Toggle Packet bit

1 = Transmit a Data 1 packet or Check received PID = DATA1, if DTS = 1

0 = Transmit a Data 0 packet or Check received PID = DATA0, if DTS = 1

bit 5 KEEP: BD Keep Enable bit

1 = USB will keep the BD indefinitely once UOWN is set

U1STAT FIFO will not be updated and TRNIF bit will not be set at the end of each transaction.

0 = USB will hand back the BD once a token has been processed

bit 4 NINC: DMA Address Increment Disable bit

1 = DMA address increment disabled

0 = DMA address increment enabled

bit 3 DTS: Data Toggle Synchronization Enable bit

1 = Data Toggle Synchronization is enabled – data packets with incorrect sync value will be ignored

0 = No Data Toggle Synchronization is performed

Note: Expected value of DATA PID (DATA0/DATA1) specified in the DATA0/1 field.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

bit 2 BSTALL: Buffer Stall Enable bit

1 = Buffer STALL enabled

STALL handshake issued if a token is received that would use the BD in the given location (UOWN bit

remains set, BD value is unchanged).

Corresponding EPSTALL bit will get set on any STALL handshake.

0 = Buffer STALL disabled

bit 1-0 Reserved

Address Offset +4

bit 31-0 BUFFER_ADDRESS<31:0>: Buffer Address bits(1)

Starting point address of the endpoint packet data buffer.

Note 1: The individual buffer addresses in the BDT must be physical memory addresses.

PIC32 Family Reference Manual

Buffer descriptor status format, in which hardware writes the descriptor and hands it back to

software, is shown in Figure 27-4.

Figure 27-4: USB Buffer Descriptor Status Format: Hardware to Software

Address Offset +0

31 26 25 16 15 8 7 6 5 4 3 2 1 0

—BYTE_COUNT<9:0> —

UOWN

DATA0/1

PID<3:0> —

Address Offset +4

31 0

BUFFER_ADDRESS<31:0>

Address Offset +0

bit 31-26 Reserved

bit 25-16 BYTE_COUNT<9:0>: Byte Count bits

Byte count reflects the actual number of bytes received or transmitted.

bit 15-8 Reserved

bit 7 UOWN: USB Own bit

1 = USB OTG module owns the BD and its corresponding buffer

CPU must not modify the BD or the buffer.

0 = CPU owns the BD and its corresponding buffer

Note: This bit can be programmed by either the CPU or the USB OTG module, and it must be initialized

by the user to the desired value prior to enabling the USB endpoint.

bit 6 DATA0/1: Data Toggle Packet bit

1 = Data 1 packet received

0 = Data 0 packet received

Note: This bit is unchanged when a packet is transmitted.

bit 5-2 PID<3:0>: Packet Identifier bits

The current token PID when a transfer completes.

The values written back are the token PID values from the USB specification: 0x1 for an OUT token, 0x9 for

an IN token or 0xd for a SETUP token.

In Host mode, this field is used to report the last returned PID or a transfer status indication.

The possible values returned are: 0x3 DATA0, 0xb DATA1, 0x2 ACK, 0xe STALL, 0xa NAK, 0x0 Bus

Time-out and 0xf Data Error.

bit 1-0 Reserved

Address Offset +4

bit 31-0 BUFFER_ADDRESS<31:0>: Buffer Address bits

Starting point address of the endpoint packet data buffer.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

Figure 27-5: Buffer Management Overview

27.3.5.4 BUFFER DESCRIPTOR CONFIGURATION

The UOWN, DTS and BSTALL bits in each BDT entry control the data transfer for the associated

buffer and endpoint.

Setting the DTS bit enables the USB OTG module to perform data toggle synchronization. When

DTS is enabled: if a packet arrives with an incorrect DTS, it will be ignored, the buffer remains

unchanged, and the packet will be NAK’d (Negatively Acknowledged).

Setting the BSTALL bit causes the USB to issue a STALL handshake if a token is received by the

SIE that would use the BD in this location – the corresponding EPSTALL bit is set and a STALLIF

interrupt is generated. When the BSTALL bit is set, the BD is not consumed by the USB OTG

module (the UOWN bit remains set and the rest of the BD values are unchanged). If a SETUP

token is sent to the stalled endpoint, the module automatically clears the corresponding BSTALL

bit.

The byte count represents the total number of bytes that are transmitted or received. Valid byte

counts range from 0 to 1023. For all endpoint transfers, the byte count is updated by the USB

OTG module, with the actual number of bytes transmitted or received, after the transfer is com-

pleted. If number of bytes received exceeds the corresponding byte count value written by the

firmware, the overflow bit is set and the data is truncated to fit the size of the buffer (as given in

the BDT).

U1BDTP<1:3>

Pointer

BDT

located in RAM(1)

EP0 RX EVEN Descriptor

EP0 RX ODD Descriptor

EP0 TX EVEN Descriptor

EP0 TX ODD Descriptor

EP1 RX EVEN Descriptor

EP1 RX ODD Descriptor

EP1 TX EVEN Descriptor

EP1 TX ODD Descriptor

EP2 RX EVEN Descriptor

EP2 RX ODD Descriptor

EP2 TX EVEN Descriptor

EP2 TX ODD Descriptor

...

EP15 TX ODD Descriptor

Transfer Buffers

Located in

RAM or Flash(2)

EP0 RX EVEN Buffer

EP0 RX ODD Buffer

EP0 TX EVEN Buffer

EP0 TX ODD Buffer

EP1 RX EVEN Buffer

EP1 RX ODD Buffer

EP1 TX EVEN Buffer

EP1 TX ODD Buffer

EP2 RX EVEN Buffer

EP2 RX ODD Buffer

EP2 TX EVEN Buffer

EP2 TX ODD Buffer

...

EP15 TX ODD Buffer

Note 1: 512-byte aligned.

2: Data to be transmitted may be located in Flash memory.

Buffers receiving data must be located in RAM.

PIC32 Family Reference Manual

27.3.6 Hardware Interface

27.3.6.1 POWER SUPPLY REQUIREMENTS

Power supply requirements for USB implementation vary with the type of application, and are

outlined below.

• Device:

Operation as a device requires a power supply for the PIC32 and the USB transceiver, see

Figure 27-6 for an overview of USB implementation as a device.

• Embedded Host:

Operation as a host requires a power supply for the PIC32, the USB transceiver, and a 5V

nominal supply for the USB VBUS. The power supply must be able to deliver 100 mA, or up

to 500 mA, depending on the requirements of the devices in the TPL. The application dic-

tates whether the VBUS power supply can be disabled or disconnected from the bus by the

PIC32 application. Figure 27-7 illustrates an overview of USB implementation as a host.

• OTG Dual Role:

Operation as an OTG dual role requires a power supply for the PIC32, the USB transceiver,

and a switchable 5V nominal supply for the USB VBUS. An overview of USB implementation

as OTG is presented in Figure 27-8.

When acting as an A-device, power must be supplied to VBUS. The power supply must be

able to deliver 8 mA, 100 mA or up to 500 mA, depending on the requirements of the

devices in the TPL.

When acting as a B-device, power must not be supplied to VBUS. VBUS pulsing can be

performed by the USB OTG module or by a capable power supply.

27.3.6.2 VBUS REGULATOR INTERFACE

The VBUSON output can be used to control an off-chip 5V VBUS regulator. The VBUSON pin is

controlled by the VBUSON bit (U1OTGCON<3>). VBUSON appears in Figure 27-7 and

Figure 27-8.

Figure 27-6: Overview of USB Implementation as a Device

VUSB

D+

D-

VBUS

USB OTG

USB Type ‘B’

Connector

3.3V

0.1 µF

(1)

Note 1: See Section 7.3 “Physical Layer” in “Universal Serial Bus Specification, Revision 2.0” for the VBUS capacitance value in

a device implementation.

Module

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

Figure 27-7: Overview of USB Implementation as a Host

VUSB

D+

D-

VBUS

USB OTG

External Power

USB Type ‘A’

Connector

VBUSON

3.3V

0.1 µF

(1)

Note 1: See Section 7.3 “Physical Layer” in “Universal Serial Bus Specification, Revision 2.0” for the VBUS capacitance value in

a host implementation.

Module

PIC32 Family Reference Manual

Figure 27-8: Overview of USB Implementation for OTG (Dual Role)

VUSB

D+

D-

VBUS

USB OTG

External Power

VBUSON

SRP Source

SRP Discharge

3.3V

USB Type

Micro ‘AB’

Connector

0.1 µF

(1)

Note 1: See Section 7.3 “Physical Layer” and Section 5. “Electrical Requirements” in “Universal Serial Bus Specification,

Revision 2.0” for the VBUS capacitance value in an OTG implementation.

Module

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

27.3.7 Module Initialization

This section describes the steps that must be taken to properly initialize the USB OTG module.

27.3.7.1 ENABLING THE USB HARDWARE

In order to use the USB peripheral, software must set the USBPWR bit (U1PWRC<0>) to ‘1’. This

may be done in start-up boot sequence.

USBPWR is used to initiate the following actions:

• Start the USB clock

• Allow the USB interrupt to be activated

• Select USB as the owner of the necessary I/O pins

• Enable the USB transceiver

• Enable the USB comparators

The USB OTG module and internal registers are reset when USBPWR is cleared. Consequently,

the appropriate initialization process must be performed whenever the USB OTG module is

enabled, as described in the following subsections. Otherwise, any configuration packet sent to

the USB OTG module will be NAK’d, by hardware, until the module is configured.

27.3.7.2 INITIALIZING THE BDT

All descriptors for a given endpoint and direction must be initialized prior to enabling the endpoint

(for that direction). After a reset, all endpoints are disabled and start with the EVEN buffer for

transmit and receive directions.

Transmit descriptors must be written with the UOWN bit cleared to ‘0’ (owned by software). All

other transmit descriptor setup may be performed anytime prior to setting the UOWN bit to ‘1’.

Receive descriptors must be fully initialized to receive data. This means that memory must be

reserved for received packet data. The pointer to that memory (Physical Address), and the size

reserved in bytes, must be written to the descriptor. The receive descriptor UOWN bit should be

initialized to ‘1’ (owned by Hardware). The DTS and STALL bits should also be configured

appropriately.

If a transaction is received and the descriptor’s UOWN bit is ‘0’ (owned by software), the USB

OTG module returns a NAK handshake to the host. Usually, this causes the host to retry the

transaction.

27.3.7.3 USB ENABLE/MODE BITS

USB mode of operation is controlled by the following enable bits: OTGEN (U1OTGCON<2>),

HOSTEN (U1CON<3>) and USBEN/SOFEN (U1CON<0>).

•OTGEN: Selects whether the PIC32 is to act as an OTG part (OTGEN = 1) or not. OTG

devices support SRP and HNP in hardware with Firmware management and have direct

control over the data-line pull-up and pull-down resistors.

•HOSTEN: Controls whether the part is acting in the role of USB Host (HOSTEN = 1) or

USB Device (HOSTEN = 0). Note that this role may change dynamically in an OTG

application.

•USBEN/SOFEN: Controls the connection to USB by enabling the D+ pull-up resistor when

the USB OTG module is not configured as a host.

If the USB OTG module is configured as a host, SOFEN controls whether the host is active

on the USB link and sends SOF tokens every 1 ms.

Note: If the USB OTG module was previously active and was quickly disabled and

re-enabled, there is a chance that the module may still be finishing the previous bus

activity. In this situation, the firmware should wait for the USBBUSY bit

(U1PWRC<3>) to become cleared before attempting to configure and enable the

module. Please note that this feature is not available in all devices. Refer to the

specific device data sheet for details.

Note: The other USB OTG module control registers should be properly initialized before

enabling USB via these bits.

PIC32 Family Reference Manual

27.3.8 Device Operation

All communication on the USB is initiated by the host. Therefore, in device mode, when USB is

enabled USBEN = 1 (U1CON<0>), endpoint 0 must be ready to receive control transfers. Initial-

ization of the remaining endpoints, descriptors and buffers can be delayed until the host selects

a configuration for the device. Refer to Chapter 9 of “Universal Serial Bus Specification,

Revision 2.0” for more information on this subject.

The following steps are performed to respond to a USB transaction:

1. Software pre-initializes the appropriate BDs, and sets the UOWN bits to ‘1’ to be ready for

a transaction.

2. Hardware receives a TOKEN PID (IN, OUT, SETUP) from the USB host, and checks the

appropriate BD.

3. If the transaction will be transmitted (IN), the module reads packet data from data memory.

4. Hardware receives a DATA PID (DATA0/1), and sends or receives the packet data.

5. If a transaction is received (SETUP, OUT), the module writes packet data to data memory.

6. The module issues, or waits for, a handshake PID (ACK, NAK, STALL), unless the endpoint

is setup as an isochronous endpoint (EPHSHK bit UEPMx<0> is cleared).

7. The module updates the BD, and writes the UOWN bit to ‘0’ (SW owned).

8. The module updates the U1STAT register, and sets the TRNIF interrupt.

9. Software reads the U1STAT register, and determines the endpoint and direction for the

transaction.

10. Software reads the appropriate BD, completes all necessary processing, and clears the

TRNIF interrupt.

27.3.8.1 RECEIVING AN IN TOKEN IN DEVICE MODE

Perform the following steps when an IN token is received in Device mode:

1. Attach to a USB host and enumerate as described in Chapter 9 of “Universal Serial Bus

Specification, Revision 2.0”.

2. Populate the data buffer with the data to send to the host.

3. In the appropriate (EVEN or ODD) transmit buffer descriptor for the desired endpoint:

a) Set up the control bit fields with the correct data toggle (DATA0/1) value and the byte

count of the data buffer.

b) Set up the address bit field with the starting address of the data buffer.

c) Set the UOWN bit field to ‘1’.

4. When the USB OTG module receives an IN token, it automatically transmits the data in

the buffer. Upon completion, the module updates the status bit fields, and sets the transfer

complete interrupt bit, TRNIF(U1IR<3>).

27.3.8.2 RECEIVING AN OUT TOKEN IN DEVICE MODE

Perform the following steps when an OUT token is received in Device mode:

1. Attach to a USB host and enumerate as described in Chapter 9 of “Universal Serial Bus

Specification, Revision 2.0”.

2. Create a data buffer with the amount of data you are expecting from the host.

3. In the appropriate (EVEN or ODD) transmit buffer descriptor for the desired endpoint:

a) Set up the control bit fields with the correct data toggle (DATA0/1) value and the byte

count of the data buffer.

b) Set up the address bit field with the starting address of the data buffer.

c) Set the UOWN bit of the control bit field to ‘1’.

4. When the USB OTG module receives an OUT token, it will automatically transfer the data

the host sent into the buffer. Upon completion, the module updates the status bit fields,

and sets the transfer complete interrupt bit, TRNIF(U1IR<3>).

Note: For transmitted (IN) transactions (host reading data from the device), the read data

must be ready when the Host begins USB signaling. Otherwise, the USB OTG

module will send a NAK handshake if UOWN is ‘0’.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

27.4 HOST MODE OPERATION

In Host mode, only endpoint 0 is used (all other endpoints should be disabled). Since the host

initiates all transfers, the BD does not require immediate initialization. However, the BDs must be

configured before a transfer is initiated – which is done by writing to the U1TOK register.

The following sections de mode tasks. In Host mode, USBscribe how to perform common Host

transfers are invoked explicitly by the host software. The host software is responsible for initiating

the setup, data, and status stages of all control transfers. The acknowledge (ACK or NAK) is gen-

erated automatically by the hardware, based on the CRC. Host software is also responsible for

scheduling packets so that they do not violate USB protocol. All transfers are performed using

the Endpoint 0 Control register (U1EP0) and BDs.

27.4.1 Configuring the SOF Threshold

The module counts down the number of bits that could be transmitted within the current USB

full-speed frame. Since 12,000 bits can be transmitted during the 1 ms frame time, a counter (not

visible to software) is loaded with the value ‘12,000’ at the start of each frame. The counter

decrements once for each bit time in the frame. When the counter reaches zero, the next frame’s

SOF packet is transmitted, see Figure 27-9.

The SOF threshold register (U1SOF) is used to ensure that no new tokens are started too close

to the end of a frame. This prevents a conflict with the next frame’s SOF packet. When the coun-

ter reaches the threshold value of the U1SOF register (the value in the U1SOF register is in terms

of bytes), no new tokens are started until after the SOF has been transmitted. Thus, the USB

OTG module attempts to ensure that the USB link is idle when the SOF token needs to be

transmitted.

This implies that the value programmed into the U1SOF register must reserve enough time to

ensure the completion of the worst-case transaction. Typically, the worst-case transaction is an

IN token followed by a maximum-sized data packet from the target, followed by the response

from the host. If the host is targeting a low-speed device that is bridging through a full-speed hub,

the transaction will also include the special PRE token packets.

Figure 27-9: Allocation of Bits for a Full-Speed Frame

Table 27-3 and Table 27-4 show examples of calculating worst-case bit times.

SOF SOF

U1SOF * 8

bit times

0 ms 1 ms (12,000 bit times)

Note: Drawing is not to scale.

SOF Threshold

1 Full-Speed Frame

Note 1: While the U1SOF register value is described in terms of bytes, these examples

show the result in terms of bits.

2: In Table 27-4, the IN, DATA and HANDSHAKE packets are transmitted at

low-speed (8 times slower than full-speed).

3: These calculations do not take the possibility that the packet data needs to be

bit-stuffed for NRZI encoding into account.

PIC32 Family Reference Manual

Table 27-3: Example of SOF Threshold Calculation: Full-Speed

Packet Fields Bits

IN SYNC, PID, ADDR, ENDP, CRC5, EOP 35

Turnaround(1) — 8

DATA SYNC, PID, DATA(2), CRC16, EOP 547

Turnaround — 2

HANDSHAKE SYNC, PID, EOP 19

Inter-packet — 2

Total 613

Note 1: Inter-packet delay of 2. An additional 5.5 bit times of latency is added to represent a worst-case

propagation delay through 5 hubs.

2: Using 64 bytes maximum packet size for this example calculation.

Table 27-4: Example of SOF Threshold Calculation: Low-Speed Via Hub

Packet Fields Bits FS Bits

PRE SYNC, PID 16 16

Hub setup — 4 4

IN SYNC, PID, ADDR, ENDP, CRC5, EOP 35 280

Turnaround(1) — 8 8

DATA SYNC, PID, DATA(2), CRC16, EOP 99 792

Turnaround — 2 2

PRE SYNC, PID 16 16

HANDSHAKE SYNC, PID, EOP 19 152

Inter-packet — 2 2

Total 1272

Note 1: Inter-packet delay of 2. An additional 5.5 bit times of latency is added to represent a worst-case

propagation delay through 5 hubs.

2: Packets limited to 8 bytes maximum in Low-Speed mode.

Note: Refer to Section 5.11.3 “Calculating Bus Transaction Times” in “Universal Serial Bus Specification,

Revision 2.0” for details on calculating bus transaction time.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

27.4.2 Enabling Host Mode and Discovering a Connected Device

To enable Host mode, perform the following steps:

1. Enable Host mode, the HOSTEN bit (U1CON<3>) = 1.

This enables the D+ and D- pull-down resistors, and disables the D+ and D- pull-up

resistors. To reduce noise on the bus, disable the SOF packet generation by writing the

SOF enable bit to ‘0’, the SOFEN bit (U1CON<0>) = 0.

2. Enable the device attach interrupt, the ATTACHIE bit (U1IE<6> = 1).

3. Wait for the device attach interrupt, the ATTACHIF bit (U1IR<6>).

This is signaled by the USB device changing the state of D+ or D- from ‘0’ to ‘1’ (SE0 to

JSTATE). After it occurs, wait for the device power to stabilize (10 ms is minimum, 100 ms

is recommended).

4. Check the state of the JSTATE and SE0 bits in the control register U1CON.

If the JSTATE bit (U1CON<7>) is ‘0’, the connecting device is low-speed; otherwise, the

device is full-speed.

5. If the connecting device is low-speed, set the low-speed enable bit in the address register,

the LSPDEN bit (U1ADDR<7>= 1), and the low-speed bit in the Endpoint 0 Control

6. Reset the USB device by sending the Reset signaling for at least 50 ms (USBRST bit

(U1CON<4>) = 1). After 50 ms, terminate the Reset (USBRST bit (U1CON<4>) = 0).

7. Enable SOF packet generation to keep the connected device from going into Suspend

(SOFEN bit (U1CON<0>) = 1).

8. Wait 10 ms for the device to recover from Reset.

9. Perform enumeration as described in Chapter 9 of “Universal Serial Bus Specification,

Revision 2.0”.

27.4.2.1 HOST TRANSACTIONS

When acting as a host, a transaction consists of the following:

1. Software configures the appropriate BD, and sets the UOWN bit to ‘1’ (HW owned).

2. Software checks the state of the TOKBUSY bi fy that any previoust (U1CON<5>) to veri

transaction has completed.

3. Software writes the address of the target device in the U1ADDR register.

4. Software writes the endpoint number and the desired TOKEN PID (IN, OUT or SETUP) to

the U1TOK register.

5. Hardware reads the BD to determine the appropriate action, and to obtain the pointer to

data memory.

6. Hardware issues the correct TOKEN PID (IN, OUT, SETUP) on the USB link.

7. If the transaction is a transmit transaction (OUT, SETUP), the USB OTG module reads the

packet data out of data memory. Then the module follows with the desired DATA PID

(DATA0/DATA1) and packet data.

8. If the transaction is a receive transaction (IN), the USB OTG module waits to receive the

DATA PID and packet data. Hardware writes the packet data to memory.

9. Hardware issues or waits for a Handshake PID (ACK, NAK or STALL), unless the endpoint

is set up as an Isochronous Endpoint (EPHSHK bit (U1EPx<0>) is cleared).

10. Hardware updates the BD, and writes the UOWN bit to ‘0’ (SW owned).

11. Hardware updates the U1STAT register, and sets the TRNIF bit (U1IR<3>) interrupt.

12. Hardware reads the next BD (EVEN or ODD) to see whether it is owned by the USB OTG

module. If it is, hardware begins the next transaction.

13. Software should read the U1STAT register, and then clear the TRNIF interrupt.

If Software does not set the UOWN bit to ‘1’ in the appropriate BD prior to writing the U1TOK

PIC32 Family Reference Manual

27.4.3 Completing a Control Transaction to a Connected Device

Complete all of the following steps to discover a connected device:

1. Set up the Endpoint Control register for bidirectional control transfers,

U1EP0<4:0> = 0x0D.

2. Place an 8-byte device setup packet in the appropriate memory buffer. See Chapter 9 of

“Universal Serial Bus Specification, Revision 2.0” for information on the device framework

command set.

3. Initialize the current (EVEN or ODD) TX EP0 BD to transfer the 8-byte device framework

command (for example, a GET DEVICE DESCRIPTOR command).

a) Set the BD control offset 0 to 0x8008 (UOWN bit set, byte count of 8).

b) Set the BD data buffer address (BD0ADR) to the starting address of the 8-byte

memory buffer containing the command, if it is not already initialized.

4. Set the USB address of the target device in the address register U1ADDR<6:0>. After a

USB bus Reset, the device USB address will be zero. After enumeration, it must be set to

another value, between 1 and 127, by the host software.

5. Write the token register with a SETUP command to Endpoint 0, the target device’s default

control pipe (U1TOK = 0xD0). This will initiate a SETUP token on the bus followed by a

data packet. The device handshake will be returned in the PID field of BD status after the

packets complete. When the module updates BD status, a transfer done interrupt will be

asserted (U1IR<TRNIF>). This completes the setup stage of the setup transfer as

described in Chapter 9 of the USB specification.

6. To initiate the data stage of the setup transaction (for example, get the data for the GET

DEVICE DESCRIPTOR command), set up a buffer in memory to store the received data.

7. Initialize the current (EVEN or ODD) RX or TX (RX for IN, TX for OUT) EP0 BD to transfer

the data.

a) Set the BD control UOWN bit to ‘1’, data toggle (DTS) to DATA1 and byte count to the

length of the data buffer.

b) Set the BD data buffer address (BD0ADR) to the starting address of the data buffer

if it is not already initialized.

8. Write the Token register with the appropriate IN or OUT token to Endpoint 0 (the target

device’s default control pipe), for example, an IN token for a GET DEVICE DESCRIPTOR

command (U1TOK = 0x90). This will initiate an IN token on the bus followed by a data

packet from the device to the host. When the data packet completes, the BD status is written

and a transfer done interrupt will be asserted (TRNIF bit (U1IR<3>)). For control transfers

with a single packet data phase, this completes the data phase of the setup transaction. If

more data needs to be transferred, return to step 6.

9. To initiate the status stage of the setup transaction, set up a buffer in memory to receive

or send the zero length status phase data packet.

10. Initialize the current (EVEN or ODD) TX EP0 BD to transfer the status data.

a) Set the BD control to 0x8000 (UOWN bit to ‘1’, data toggle (DTS) to DATA0 and byte

count to ‘0’).

b) Set the BDT buffer address field to the start address of the data buffer.

11. Write the Token register with the appropriate IN or OUT token to Endpoint 0, (the target

device’s default control pipe) for example, an OUT token for a GET DEVICE DESCRIPTOR

command (U1TOK = 0x10). This will initiate a token on the bus, followed by a zero length

data packet from the host to the device. When the data packet completes, the BD is

updated with the handshake from the device, and a transfer done interrupt (TRNIF bit

(U1IR<3>)) will be asserted . This completes the status phase of the setup transaction.

Note: Some devices can only effectively respond to one transaction per frame.

Section 27. USB On-The-Go (OTG)

USB On-The-Go

(OTG)

27.4.4 Data Transfer with a Target Device

Complete all of the following steps to discover and configure a connected device.

1. Write the EP0 Control register (U1EPn) to enable transmit and receive transfers as appro-

priate with handshaking enabled (unless isochronous transfers are to be used). If the tar-

get device is a low-speed device, also set the Low-Speed Enable bit, the LSPD bit

(U1EPn<7>). If you want the hardware to automatically retry indefinitely if the target

device asserts a NAK on the transfer, clear the Retry Disable bit, RETRYDIS (U1EPn<6>).

2. Set up the current Buffer Descriptor (EVEN or ODD) in the appropriate direction to transfer

the desired number of bytes.

3. Set the address of the target device in the address register (U1ADDR<6:0>).

4. Write the Token register (U1TOK) with an IN or OUT token as appropriate for the desired

endpoint. This triggers the module’s transmit state machines to begin transmitting the

token and the data.

5. Wait for the transfer done interrupt (TRNIF bit (U1IR<3>)). This will indicate that the BD

has been released back to the microprocessor and the transfer has completed. If the retry

disable bit is set, the handshake (ACK, NAK, STALL or ERROR (0xf)) will be returned in

the BD PID field. If a stall interrupt occurs, then the pending packet must be dequeued and

the error condition in the target device cleared. If a detach interrupt occurs (SE0 for more

than 2.5 μs), then the target has detached (DETACHIF bit (U1IR<0>)).

6. Once the transfer done interrupt (TRNIF bit (U1IR<3>)) occurs, the BD can be examined

and the next data packet queued by returning to step 2.

27.4.4.1 USB LINK STATES

Three possible link states are described in the following subsections:

• Reset

• Idle and Suspend

• Resume Signaling

27.4.4.1.1 Reset

As a host, software is required to drive Reset signaling. It may do this by setting the USBRST bit

(U1CON<4>). As per the USB specification, the host must drive the Reset for at least 50 ms. (This

does not have to be continuous Reset signaling. Refer to “Universal Serial Bus Specification, Revi-

sion 2.0” for more information.) Following Reset, the host must not initiate any downstream traffic

for another 10 ms.

As a device, the USB OTG module will assert the URSTIF bit (U1IR<0>) interrupt when it has

detected Reset signaling for 2.5 μs. Software must perform any Reset initialization processing at

this time. This includes setting the Address register to 0x00 and enabling Endpoint 0. The

URSTIF interrupt will not be set again until the Reset signaling has gone away and then has been

detected again for 2.5 μs.

Note: Use of automatic indefinite retries can lead to a deadlock condition if the device

never responds.

Note: USB speed, transceiver and pull-ups should only be configured during the module

setup phase. It is not recommended to change these settings while the module is

enabled.

PIC32 Family Reference Manual

27.4.4.1.2 Idle and Suspend

The Idle state of the USB is a constant J state. When the USB has been Idle for 3 ms, a device

should go into Suspend state. During active operation, the USB host will send a SOF token every

1 ms, preventing a device from going into Suspend state.

Once the USB link is in the Suspend state, a USB host or device must drive resume signaling

prior to initiating any bus activity. (The USB link may also be disconnected).

As a USB host, software should consider the link in Suspend state as soon as software clears

the SOFEN bit (U1CON<0>).

As a USB device, hardware will set the IDLEIF bit (U1IR<4>) interrupt when it detects a constant

Idle on the bus for 3 ms. Software should consider the link in Suspend state when the IDLEIF

interrupt is set.

When a Suspend condition has been detected, the software may wish to place the USB hard-

ware in a Suspend mode by setting the USUSPEND bit (U1PWRC<1>). The hardware Suspend

mode gates the USB OTG module’s 48 MHz clock and places the USB transceiver in a

Low-Power mode.

Additionally, the user may put the PIC32 into Sleep mode while the link is suspended.

27.4.4.1.3 Driving Resume Signaling

If software wants to wake the USB from Suspend state, it may do so by setting the RESUME bit

(U1CON<2>). This will cause the hardware to generate the proper resume signaling (including

finishing with a low-speed EOP if in host mode).

A USB device should not drive resume signaling unless the Idle state has persisted for at least

5 ms. The USB host also must have enabled the function for remote wake-up.

Software must set RESUME for 1-15 ms if a USB device, or greater than 20 ms if a USB host,

then clear it to enable remote wake-up. For more information on RESUME signaling, see

Section 7.1.7.7, 11.9, and 11.4.4 in “Universal Serial Bus Specification, Revision 2.0”.

Writing RESUME will automatically clear the special hardware Suspend (low-power) state.

If the part is acting as a USB host, software should, at minimum, set the SOFEN bit (U1CON<0>)

after driving its resume signaling. Otherwise, the USB link would return right back to the Suspend

state after 3 ms of inactivity. Also, software must not initiate any downstream traffic for 10 ms

following the end of resume signaling.

27.4.4.1.4 Receiving Resume Signaling

When the USB logic detects resume signaling on the USB bus for 2.5 μs, hardware will set the

resume interrupt bit, RESUMEIF (U1IR<5>).

A device receiving resume signaling must prepare itself to receive normal USB activity. A host

receiving resume signaling must immediately start driving resume signaling of its own. The

special hardware Suspend (low-power) state is automatically cleared upon receiving any activity

on the USB link.

Reception of any activity on the USB link (this may be due to resume signaling or a link discon-

nect) while the PIC32 is in Sleep mode will cause the ACTVIF bit (U1OTGIR<4>) interrupt to be

set. This will cause wake-up from Sleep.

27.4.4.2 SRP SUPPORT

SRP support is not required by non-OTG applications. SRP may only be initiated at full-speed.

Refer to the On-The-Go Supplement specification for more information regarding SRP.

An OTG A-device or embedded host may decide to power-down the VBUS supply when it is not

using the USB link. Software may do this by clearing the VBUSON bit (U1OTGCON<3>). When

the VBUS supply is powered down, the A-device is said to have ended a USB session.

Note: When the A-device powers down the VBUS supply, the B-device must disconnect its

pull-up resistor.

Product specificaties

Merk:	Microchip
Categorie:	Niet gecategoriseerd
Model:	PIC32MX250F128D

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