ST STM32F412

RM0402 Rev 6 1093/1163
RM0402 USB on-the-go full-speed (OTG_FS)
1122
Figure 350. Isochronous IN transactions
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
MSv36021V1
HostApplication AHB
write
_
tx
_
fifo
(
ch_1
)
init_re
g(
ch_1
)
write_tx_
f
i
f
o
(
ch_1
)
ch_2
Periodic Request
Queue
Assume that this queue
can hold 4 entries.
1
5
MPS
2
3
3
4
6
3
init_reg
(
ch_1
)
write_tx_
f
i
f
o
(
ch_1
)
init_reg
(
ch_1
)
5
4
Even
(micro)
frame
Odd
(micro)
frame
DeviceUSB
7
9
6
set_ch_en
(ch_2)
init_reg(ch_2)
read_rx_sts
read_rx_fifo
read_rx_sts
set_ch_en
(ch_2)
init_reg(ch_2)
1
2
RxFLvl interrupt
RxFLvl interrupt
XferCompl interrupt
XferCompl interrupt
OUT
IN
IN
OUT
ch_2
ch_1
ch 1
8
ch_1
ch 1
1
M
P
S
1
M
P
S
1
M
P
S
1
XferCompl interrupt
DATA0
MPS
DATA0
MPS
DATA0
DATA0