Communication Processor Module
MOTOROLA MPC823e REFERENCE MANUAL 16-417
SMC
COMMUNICATION
16
PROCESSOR MODULE
CLEN—Character Length
This field is programmed with a value between 3 and 15 to obtain 4 to 16 bits per character.
If the character length is less than 8 bits, the MSBs of the byte in buffer memory are not used
on transmit and are written with zeros on receive. On the other hand, if the character length
is more than 8 bits but less than 16 bits, the MSBs of the half-word in buffer memory are not
used on transmit and are written with zeros on receive.
BS—Byte Sequence
This bit controls the sequence of byte transmission if the REVD bit is set for a character
length greater than 8 bits. It must be set to zero to maintain behavior compatibility with the
MC68360 QUICC microprocessor.
0 = Normal mode. This must be selected if the character length is less than
or equal to 8 bits.
1 = Transmit lower address byte first.
REVD—Reverse Data
0 = Normal mode.
1 = Reverse the character bit order. The MSB is transmitted first.
SM—SMCx Mode
00 = GCI or SCIT mode.
01 = Reserved.
10 = UART mode.
11 = Totally transparent mode. This must be selected for SMCx transparent operation.
DM—Diagnostic Mode
00 = Normal mode.
01 = Local loopback mode.
10 = Echo mode.
11 = Reserved.
TEN—SMCx Transmit Enable
0 = SMCx transmitter disabled.
1 = SMCx transmitter enabled.
Note: Erratic behavior will occur if you do not write the values 0 to 2 to CLEN. Larger
character lengths increase the potential performance of the SMCx channel and
lower the performance impact of other channels. For instance, using 16-bit
characters, rather than 8-bit characters is recommended if 16-bit characters are
acceptable in the final application.
Note: Once the TEN bit is cleared, it must not be reenabled for at least
three serial clocks.
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