Rainbow Electronics AT91CAP9S250A - Manual (Page 861)

861
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
Figure 44-11. Autovalid with DMA
Note: In the illustration above Autovalid validates a bank as full, although this might not be the case, in order to continue processing
data and to send to DMA.
44.4.8.7 Isochronous IN
Isochronous-IN is used to transmit a stream of data whose timing is implied by the delivery rate.
Isochronous transfer provides periodic, continuous communication between host and device.
It guarantees bandwidth and low latencies appropriate for telephony, audio, video, etc.
If the endpoint is not available (TX_PK_RDY = 0), then the device does not answer to the host.
An ERR_FL_ISO interrupt is generated in the UDPHS_EPTSTAx register and once enabled,
then sent to the CPU.
The STALL_SNT command bit is not used for an ISO-IN endpoint.
44.4.8.8 High Bandwidth Isochronous Endpoint Handling: IN Example
For high bandwidth isochronous endpoints, the DMA can be programmed with the number of
transactions (BUFF_LENGTH field in UDPHS_DMACONTROLx) and the system should provide
Bank 0 Bank 1 Bank 0 Bank (usb)
Write write bank 0 write bank 1 write bank 0
Bank 0 Bank (system) Bank 1 Bank 0 Bank 1
Virtual TX_PK_RDY Bank 0
Virtual TX_PK_RDY Bank 1
TX_PK_RDY
(Virtual 0 & Virtual 1)
bank 0 is full bank 1 is full bank 0 is full
IN data 0 IN data 1 IN data 0
Bank 1
Bank 1 Bank 0