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Communication Processor Module
MOTOROLA
MPC823 USER’S MANUAL
16-219
SCC2
COMMUNICATION
16
PROCESSOR
MODULE
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 should 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 choose between either no delay between buffers transmitted in SCC2
UART mode, or a more accurate CTS 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 CTS lost condition. Asynchronous flow control, however, continues to
function normally.
1 = Normal CTS 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.