RM0090: Reference manual - STMicroelectronics

RM0090 USB on-the-go full-speed (OTG_FS)
● Isochronous OUT transactions
A typical isochronous OUT operation is shown in Figure 371. The assumptions are:
– The application is attempting to send one packet every frame (up to 1 maximum
packet size), starting with an odd frame. (transfer size = 1 024 bytes).
– The periodic transmit FIFO can hold one packet (1 KB).
– Periodic request queue depth = 4.
The sequence of operations is as follows:
a) Initialize and enable channel 1. The application must set the ODDFRM bit in
OTG_FS_HCCHAR1.
b) Write the first packet for channel 1.
c) Along with the last Word write of each packet, the OTG_FS host writes an entry to
the periodic request queue.
d) The OTG_FS host attempts to send the OUT token in the next frame (odd).
e) The OTG_FS host generates the XFRC interrupt as soon as the last packet is
transmitted successfully.
f) In response to the XFRC interrupt, reinitialize the channel for the next transfer.
g) Handling non-ACK responses
Doc ID 018909 Rev 3 1124/1416