Analog Devices ADSP-SC58 Series Hardware Reference Manual page 1429

At least one USB packet always is sent. The number of further USB packets sent in the same micro-frame depends
on the amount of data loaded into the FIFO. The USB_EP[n]_TXCSR_P.TXPKTRDY bit is cleared and an in-
terrupt is generated only when all the packets have been sent. Each USB packet is sent in response to an IN token.
If, at the end of a micro-frame, the USB controller has not received enough IN tokens to send all the USB packets,
the remaining data is flushed from the FIFO. (For example, one of the IN tokens received is corrupt). The
USB_EP[n]_TXCSR_P.TXPKTRDY bit is cleared and the USB_EP[n]_TXCSR_P.INCOMPTX bit is set to
indicate that not all of the data loaded into the FIFO transmitted.
High-Bandwidth Isochronous or Interrupt OUT Endpoints
In high-speed mode, isochronous receive endpoints can receive up to three USB packets in any micro-frame. The
reception occurs with a payload of up to 1024 bytes in each packet, corresponding to a data transfer rate of up to
3072 bytes per micro-frame. Similarly, the USB controller can receive high-bandwidth interrupt transactions in host
mode, but there is no support for high-bandwidth interrupt transactions in peripheral mode.
The High-Bandwidth OUT Endpoints figure shows an overview of high-bandwidth OUT endpoints.
The USB controller supports this rate by automatically combining all the USB packets received during a micro-
frame into a single packet of up to 3 normal packets within the receive FIFO. From the software viewpoint in the
processor core, the High Bandwidth IN Endpoints figure describes the operation for single or double packet buffer-
ing (as appropriate). One exception is that the USB_EP[n]_RXCSR_P.RXPKTRDY bit always must be cleared
manually (for example by the processor core) because the auto-clear function does not operate with high-bandwidth
isochronous transfers.
The maximum number of USB packets that can be received in any micro-frame and the maximum payload of these
packets are configured as follows:
• Use the USB_EP[n]_RXMAXP.MAXPAY bits to set the maximum payload in any USB packet
• Use the USB_EP[n]_RXMAXP.MULTM1 bits to set the maximum number of these packets that can be re-
ceived in a micro-frame (2 or 3)
ADSP-SC58x/ADSP-2158x SHARC+ Processor Hardware Reference
Peripheral Mode
27–17