UPSD3422 datasheet(289/293 Pages) STMICROELECTRONICS

289 / 293 page

uPSD34xx

Important notes

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implemented then this extra and unexpected data packet would result in a communication

breakdown.

Workaround

Revision A and B - In the USB ISR, when an INx (x = the endpoint number of the IN FIFO)

interrupt is detected, the IN FIFOs respective busy bit should be unconditionally cleared.

The uPSD3400 USB firmware implements this workaround.

34.7

IN FIFO Pairing Operation

Description

When FIFO pairing is used on IN endpoints, an erroneous resend of a data packet may

occur. See the "Erroneous Resend of Data Packet" note as it also applies when IN FIFO

pairing is used.

Impact On Application

See the "Erroneous Resend of Data Packet" note as the impact is the same when IN FIFO

pairing is used.

Workaround

Revision A and B - See the "Erroneous Resend of Data Packet" note as the workaround is

the same when IN FIFO pairing is used.

34.8

OUT FIFO Pairing Operation

Description

When data packets are received from the host and FIFO pairing is used, the paired FIFOs

may get out of order.

Impact On Application

The received data packets are read out of order compared to the way they were sent from

the host. If the workaround is not implemented, the out of order packets would result in a

communication breakdown.

Workaround

Revision A and B - In the USB ISR, when an OUTx (x = the endpoint number of the OUT

FIFO) interrupt is detected, the OUT FIFOs respective busy bit should be unconditionally

cleared. The uPSD3400 USB firmware implements this workaround.

34.9

Missing ACK to host retransmission of SETUP packet

Description

If a host does not properly receive the ACK (due to noise) from the uPSD3400 in response

to a SETUP packet, it will resend the SETUP packet but the uPSD3400 will not respond with

UPSD3422 Datasheet(PDF) 289 Page - STMicroelectronics