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Communication Processor Module
16.10.1 Features
The following list summarizes the USB slave mode features:
• Supports USB slave mode
• Four independent endpoints support control, bulk, interrupt and isochronous data
transfers
• CRC16 generation and checking
• NRZI encoding/decoding with bit stuffing
• 12 or 1.5Mbps data rate
• Flexible data buffers with multiple buffers per frame
• Automatic retransmission upon transmit error
The following list summarizes the USB host controller features:
• Supports control, bulk, interrupt, and isochronous data transfers
• CRC16 generation and checking
• NRZI encoding/decoding with bit stuffing
• 12 and 1.5Mbps data rates (automatic generation of PRE token and data rate
configuration)
• Flexible data buffers with multiple buffers per frame
• Supports local loopback mode for diagnostics (12Mbps only)
16.10.2 Controller Limitations
The following tasks are not supported by the hardware and must be implemented by
software:
• CRC5 generation for token packets. Since CRC5 is calculated on 11 bits, this must not
impose a large CPU overhead.
• Retransmission after an error and error recovery.
• Generation and transmission of SOF token every 1ms.
• Scheduling the various transfers within frame and between frames.
• The MPC823e USB host controller does not integrate the root hub. An external hub is
required when more than one device is connected to the host.
• The host controller programming model is very similar to the function endpoint
programming model and does not conform to the Open Host Controller Interface
(OHCI). Although Motorola plans to support full host functionality, our implementation
will not be OHCI or UHCI (Universal Host Controller Interface) compatible. Those
standards define the software programming model so that software drivers can be
hardware-independent. Our implementation has a much more simplified software
interface.
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MPC823e REFERENCE MANUAL
MOTOROLA
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