Motorola MPC823e Reference Manual page 797

DATA LENGTH
This field represents the number of octets the communication processor module writes into
this buffer descriptor data buffer. It is written by the communication processor module once
the buffer is closed. When this buffer descriptor is the last buffer descriptor in the frame, the
DATA LENGTH contains the total number of frame octets (including four bytes for CRC).
Note: The actual amount of memory allocated for this buffer must be greater than or
equal to the contents of the MRBLR.
RX DATA BUFFER POINTER
This field always points to the first location of the associated data buffer, can reside in
internal or external memory, and must be divisible by four.
16.9.23.3 SCCx ETHERNET TRANSMIT BUFFER DESCRIPTOR. Data is sent to the
SCCx Ethernet controller for transmission on an SCCx channel by arranging it in buffers
referenced by the channel's transmit (TX) buffer descriptor table. Using the buffer
descriptors, the SCCx Ethernet controller confirms transmission or indicates error conditions
so that the core knows the buffers have been serviced.
0 1 2
R PAD W
OFFSET + 0
OFFSET + 2
OFFSET + 4
OFFSET + 6
NOTE: You are only responsible for initializing the items in bold.
Note: The communication processor module sets all the status bits in this buffer
descriptor, but you must clear them before submitting the buffer descriptor to the
communication processor module.
R—Ready
0 = The data buffer associated with this buffer descriptor is not ready for transmission
and you are free to manipulate this buffer descriptor or its associated data buffer.
The communication processor module clears this bit after the buffer has been
transmitted or after an error condition is encountered.
1 = The data buffer, which you have prepared for transmission, has not been
transmitted or is currently being transmitted. You cannot write any fields of this
buffer descriptor once this bit is set.
MOTOROLA
3 4 5 6 7
I L TC DEF HB LC
DATA LENGTH
TX DATA BUFFER POINTER
MPC823e REFERENCE MANUAL
Communication Processor Module
8 9 10 11 12
RL RC
13 14 15
UN CSL
16-343