Isochronous Transfers In Device Mode; Table 219. Bulk Double-Buffering Memory Buffers Usage (Host Mode) - ST STM32G0 1 Series Reference Manual

RM0444
Endpoint
type
Transmit
(OUT)
Receive
(IN)
1. Endpoint in NAK Status.
37.5.5

Isochronous transfers in Device mode

The USB standard supports full speed peripherals requiring a fixed and accurate data
production/consume frequency, defining this kind of traffic as 'isochronous'. Typical
examples of this data are: audio samples, compressed video streams, and in general any
sort of sampled data having strict requirements for the accuracy of delivered frequency.
When an endpoint is defined to be 'isochronous' during the enumeration phase, the host
allocates in the frame the required bandwidth and delivers exactly one IN or OUT packet
each frame, depending on endpoint direction. To limit the bandwidth requirements, no re-
transmission of failed transactions is possible for isochronous traffic; this leads to the fact
that an isochronous transaction does not have a handshake phase and no ACK packet is
expected or sent after the data packet. For the same reason, isochronous transfers do not
support data toggle sequencing and always use DATA0 PID to start any data packet.
Universal serial bus full-speed host/device interface (USB)

Table 219. Bulk double-buffering memory buffers usage (Host mode)

DTOG SW_BUF
0 1 (ADDRn_TX_0 / COUNTn_TX_0)
Buffer description table locations.
1 0 (ADDRn_TX_0 / COUNTn_TX_0)
Buffer description table locations
0 0
1 1
0 1
Buffer description table locations.
1 0
Buffer description table locations
0 0
1 1
Packet buffer used by
USB peripheral
USB_CHEP_TXRXBD_0
USB_CHEP_RXTXBD_0
(1)
None
(1)
None
USB_CHEP_RXTXBD_0
(ADDRn_RX_0 /
COUNTn_RX_0)
USB_CHEP_TXRXBD_0
(ADDRn_RX_0 /
COUNTn_RX_0)
(1)
None
(1)
None
RM0444 Rev 5
Packet buffer used by
Application Software
USB_CHEP_RXTXBD_0
(ADDRn_TX_1 / COUNTn_TX_1)
Buffer description table locations
USB_CHEP_TXRXBD_0
(ADDRn_TX_0 / COUNTn_TX_0)
Buffer description table locations.
USB_CHEP_TXRXBD_0
(ADDRn_TX_0 / COUNTn_TX_0)
Buffer description table locations.
USB_CHEP_RXTXBD_0
(ADDRn_TX_0 / COUNTn_TX_0)
Buffer description table locations.
USB_CHEP_TXRXBD_0
(ADDRn_RX_0 /
COUNTn_RX_0)
Buffer description table locations.
USB_CHEP_RXTXBD_0
(ADDRn_RX_0 /
COUNTn_RX_0)
Buffer description table locations.
USB_CHEP_RXTXBD_0
(ADDRn_RX_0 /
COUNTn_RX_0)
Buffer description table locations.
USB_CHEP_TXRXBD_0
(ADDRn_RX_0 /
COUNTn_RX_0)
Buffer description table locations.
1277/1390
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