TUSB8044AI datasheet(18/63 Pages) TI1

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TUSB8044A

SLLSF92 – FEBRUARY 2019

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8.3.3.1 SET REPORT (Output)

Report length includes overhead bytes (1 byte of opcode, 1 byte of device address and 2 bytes of data length)

and must match the number of bytes sent in the data stage or the request will be stalled.

•

1-byte opcode

–

8'b0000xy01 read I2C

–

8'b0000xy10 write I2C with stop

–

8'b0000xy11 write I2C without stop (use to set sub-address prior to read)

–

Bit 2 (y) when set will force 100 kHz I2C.

–

Bit 3 (x) when set will disable EP1. When EP1 is disabled, EP1 will always NAK and EP0 should be used

for Get Report.

•

1-byte I2C slave (7-bit) address

•

2-byte I2C transaction data length

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"length" bytes of Data for a write, but none for a read.

Set Report status stage reports only the status of the receipt and validity of the request, not the status of the I2C

transaction. As long as the fields construct a valid request, the status stage will be Acked by a null packet.

Otherwise, it will be STALLed. For example, if the report_length does not match the amount of data sent before

the status stage or the wLength does not match the number of bytes of data sent in the data stage, the status

stage will be STALLed.

Software shall ensure properly formatted commands and data responses. The sum of the start address and

wLength shall be less than the total size of the address range of the target device in a properly formatted

command. Hardware shall wrap any data addresses above FFFFh and shall discard any data transmitted greater

than wLength and return STALL. A STALL will also be returned if opcode is 00h.

The I2C master that performs the I2C reads and writes initiated through USB HID interface supports clock

stretching. It operates at 400 kHz by default, but can be configured for 100 kHz through eFuse or register or by

opcode.

If the TUSB8044A is suspended (L2) by the USB host, the USB HID interface must enter suspend, but the I2C

master shall remain active while attempting to complete an active I2C write request. An active I2C read request

may be aborted if the TUSB8044A enters USB suspend state. Per the USB specification, the USB host should

not suspend the HID interface while an I2C read or write is still in progress. The USB HID interface shall refuse

requests to enter USB 2.0 sleep mode (L1) while an I2C read or write is in progress.

8.3.3.2 GET REPORT (Feature)

This HID Report will always return a 2-byte constant (0x82FF) which can be used to identify compatible HID

devices even if the customer changes the VID/PID.

8.3.3.3 GET REPORT (Input)

A report length of one reports the status byte only. To receive a report with data, the report length must be the

length of the data, plus one byte for status and two bytes for the length field.

•

1-byte Status

–

0 Success

–

1 Fail — timeout (35 ms)

–

2 Fail — Address nak

–

3 Fail — data nak

•

2-byte length

•

"length" bytes of Data for a read, but not for a write.

A Get Report (input) request is required for both read and write. The interrupt and control endpoint will NAK until

the I2C transaction is complete, so that it can report length, data for a read, and final status.

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