UPSD3422 datasheet(288/293 Pages) STMICROELECTRONICS

288 / 293 page

Important notes

uPSD34xx

288/293

Workaround

Revision A and B - When a USB reset is detected, the USB SIE's registers must be

initialized appropriately by the firmware. The 3400 USB firmware examples clear USB SIE's

registers if USB reset is detected.

34.4

Data Toggle

Description

The data toggle bit is read only.

Impact On Application

The IN FIFO data toggle bit is controlled exclusively by the USB SIE; therefore, it is not

possible to change the state of the data toggle bit by firmware.

Workaround

Revision A - For cases where the data toggle bit must be reset, such as after a Clear

Feature/Stall request, sending the subsequent data on that endpoint twice results in getting

the data toggle bit back to the state that it should be.

Revision B - A change in silicon was made so that the data toggle bit is reset by disabling

and then enabling the respective endpoint's FIFO.

34.5

USB FIFO Accessibility

Description

The USB FIFO is only accessible by firmware and not by a JTAG debugger.

Impact On Application

Using a JTAG debugger, it is not possible to view the USB FIFO's contents in a memory

dump window.

Workaround

Revision A and B - None identified at this time.

34.6

Erroneous Resend of Data Packet

Description

When a data packet is sent the respective IN FIFO busy bit is not automatically cleared by

the USB SIE. This can cause a data packet to be erroneously resent to the host in response

to an IN PID immediately after the first correct transmission of this data packet.

Impact On Application

Since the Data Toggle in the retransmitted data packet is toggled from when the data was

first sent, the host will treat this packet as valid. If the identified workaround is not

UPSD3422 Datasheet(PDF) 288 Page - STMicroelectronics