Figure 350. Isochronous In Transactions - ST STM32F412 Reference Manual

RM0402
1
init_reg(ch_2)
1
2
set_ch_en
(ch_2)
2
6
6
read_rx_sts
read_rx_fifo
read_rx_sts
7
init_reg(ch_2)
9
set_ch_en
(ch_2)
1. The grayed elements are not relevant in the context of this figure.
•
Selecting the queue depth
Choose the periodic and non-periodic request queue depths carefully to match the
number of periodic/non-periodic endpoints accessed.
The non-periodic request queue depth affects the performance of non-periodic

Figure 350. Isochronous IN transactions

Application AHB
init_reg(ch_1)
write_tx_fifo
(ch_1)
MPS
init_reg(ch_1)
write_tx_fifo
(ch_1)
MPS
MPS
init_reg(ch_1)
write_tx_fifo
(ch_1)
MPS
RM0402 Rev 6
USB on-the-go full-speed (OTG_FS)
Host
3 3
1
ch_1 ch 1
ch_2
3
5
1
5
1
ch 1 ch_1
8
ch_2
1
USB
Periodic Request
Queue
Assume that this queue
can hold 4 entries.
4
DATA0
MPS
4
DATA0
DATA0
MPS
DATA0
Device
Odd
(micro)
frame
Even
(micro)
frame
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