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Communication Processor Module
PID—Packet ID
This field is set by the USB controller to indicate the type of the packet. It is only valid if the
F bit is set. This field is written by the USB controller after the received data has been placed
into the associated data buffer.
00 = This buffer contains a DATA0 packet.
01 = This buffer contains a DATA1 packet.
10 = This buffer contains a SETUP packet (DATA0).
11 = Reserved.
NO—RX Non Octet Aligned Packet
This bit indicates that a packet containing a number of bits not exactly divisible by eight has
been received. This bit is written by the USB controller after the received data has been
placed into the associated data buffer.
AB—Frame Aborted
This bit indicates that a bit stuff error has occurred during reception. This bit is written by the
USB controller after the received data has been placed into the associated data buffer.
CR—CRC Error
This bit indicates that a frame contains a CRC error. The received CRC bytes are always
written to the receive buffer. This bit is written by the USB controller after the received data
has been placed into the associated data buffer.
OV—Overrun
This bit indicates that a receiver overrun has occurred during reception. This bit is written by
the USB controller after the received data has been placed into the associated data buffer.
DATA LENGTH
This field represents the number of octets that the communication processor module has
written into this buffer descriptor's data buffer. The communication processor module writes
to this field when the buffer descriptor is closed.
Note: The actual amount of memory allocated for this buffer must be equal to the
contents of the MRBLR, plus two CRC bytes that are included in the RX buffer.
The USB device driver may strip out these two bytes before the data is sent to
your application.
RX DATA BUFFER POINTER
This field always points to the first location of the associated data buffer and must be
divisible by four. The buffer may reside in either internal or external memory.
16-368
MPC823e REFERENCE MANUAL
MOTOROLA
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