Motorola MPC823e Reference Manual page 679

R—Ready
0 = The data buffer associated with this buffer descriptor is not ready to be transmitted.
You are free to manipulate this buffer descriptor or its associated data buffer. The
communication processor module clears this bit after the buffer is transmitted or
after an error condition is encountered.
1 = The data buffer, which you must prepare for transmission, has not been
transmitted yet or is currently being transmitted. You cannot write any fields of this
buffer descriptor once this bit is set.
Bits 1 and 9–14—Reserved
These bits are reserved and must be set to 0.
W—Wrap (Final Buffer Descriptor in Table)
0 = This is not the last buffer descriptor in the TX buffer descriptor table.
1 = This is the last buffer descriptor in the TX buffer descriptor table. After this buffer
has been used, the communication processor module will transmit data from the
first buffer descriptor that TBASE points to in the table. The number of TX buffer
descriptors in this table are programmable and determined only by the W bit and
overall space constraints of the dual-port RAM.
I—Interrupt
0 = No interrupt is generated after this buffer is serviced.
1 = The TX bit in the SCCE–UART register is set when this buffer is serviced by the
communication processor module, which can cause an interrupt.
CR—Clear-to-Send Report
This bit allows you to have no delay between buffers transmitted in SCCx UART mode or a
more accurate CTSx lost error report and three bits of idle between buffers.
0 = The buffer following this buffer is transmitted with no delay (assuming it is ready),
but the CT bit may not be set in the correct TX buffer descriptor or may not be set
at all in a CTSx lost condition. Asynchronous flow control, however, continues to
function normally.
1 = Normal CTSx lost error reporting and three bits of idle occur between back-to-back
buffers.
A—Address
This bit is only valid in multidrop mode. Either automatic or manual.
0 = This buffer only contains data.
1 = Set by the core, this bit indicates that this buffer contains address characters. All
of the buffer data is transmitted as address characters.
MOTOROLA MPC823e REFERENCE MANUAL
Communication Processor Module
16-225