TUSB3410 datasheet(83/92 Pages) TI

83 / 92 page

11–13

11.9 Bootcode Programming Consideration

11.9.1 USB Requests

For each USB request, the bootcode follows the steps below to ensure proper operation of the hardware.

Determine the direction of the request by checking the MSB of the bmRequestType field and set the

USBCTL_DIR bit accordingly.

Decode the command

If another setup is pending, then return. Otherwise, serve the request.

Check again, if another setup is pending then go to step 2.

Clear the interrupt source and then the VECINT register.

Exit the interrupt routine.

11.9.1.1 USB Requests

The USB request consist of three types of transfers. They are control-read-with-data-stage, control-write-

without-data-stage, and control-write-with-data-stage transfer. In each transfer, arrows indicate interrupts generated

after receiving the setup packet, in or out token.

Figure 11–1 and Figure 11–2 show the USB data flow and how the hardware and firmware respond to the USB

requests. Table 11–9 and Table 11–10 lists the bootcode reposes to the standard USB requests.

Setup (0)

IN(1)

IN(0)

IN(0/1)

OUT(1)

INT

Packets

Setup Stage

Data Stage

StatusStage

1.Hardware generates interrupt

to MCU.

2.Hardware sets NAK on both

endpoints.

3.Set DIR bit in USBCTL to

indicate the data directory.

3.Decode the setup packet

4.If another setup packet

arrives, abandon this one.

5.Executes appropriate routines.

a) Clear NAK bit in OUT

endpoint.

b) Copy data to IN endpoint

buffer and set byte count.

1.Hardware generates interrupt to

MCU.

2.Copy data to IN buffer.

3.Clear the NAK bit.

4.If all data has been sent out,

stall input endpoint.

1.Hardware does NOT generate

interrupt to MCU.

Figure 11–1. Control Read Transfer

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