mcf5272 Freescale Semiconductor, Inc, mcf5272 Datasheet - Page 291

• Manufacturer Part Number: mcf5272
• Description: Mcf5272 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

MOTOROLA
12.4.4.1.1 IN Endpoints
The following example demonstrates how to transmit a transfer on an IN endpoint:
12.4.4.1.2 OUT Endpoints
The following example demonstrates how to handle a received transfer on an OUT
endpoint:
12.4.4.2 Isochronous Endpoints
The data flow for isochronous endpoints must be handled differently than the data flow for
non-isochronous endpoints. Data on isochronous endpoints is generally streaming data.
Therefore, there is no concept of transfers and EOT. In addition, isochronous endpoints
differ from other endpoint types in two distinct ways. Isochronous endpoints support packet
sizes up to 1023 bytes and isochronous packets are never resent. In order to support the
large packet sizes, the FIFO size can be less than two times the packet size and the EPDPn
registers are updated in real-time, not just at the end of a packet as with other endpoint
types. If the packet size is larger than the FIFO size, the FIFO level interrupt must be used.
1. Wait until the last transfer is complete (an EOT interrupt has occurred).
2. Write data to the FIFO to fill it.
3. Wait for EOP interrupt or poll EOP bit.
4. Read EPnDP to determine the number of bytes that can be written to the FIFO.
5. Write data to the FIFO to fill it or until all of the data for the transfer has been
6. Repeat steps 5–7 until all of the data for the transfer has been written to the FIFO.
7. Clear EPnCTL[IN_DONE].
8. Wait for the EOT interrupt or poll the EOT bit. The user can now begin processing
1. Wait for the EOP interrupt or poll the EOP bit.
2. Read EPnDP to determine number of bytes in the FIFO.
3. Read the indicated number of bytes of data from the FIFO into a buffer.
4. Repeat steps 1–3 until EOT is set.
5. When EOT is set, the transfer is complete. While EOT is set, the FIFO is locked and
6. Read EPnDP to determine the number of bytes in the FIFO if any for the last transfer.
7. Read the indicated number of bytes of data from the FIFO into a buffer.
8. The user can now process the received transfer.
Normally, only one packet should be written unless the software does not service the
EOP immediately.
written.
the next transfer.
any packets sent for the next transfer cause a NAK response.
The EOT bit can be cleared once this register has been read.
Chapter 12. Universal Serial Bus (USB)
Software Architecture and Application Notes
12-31