Communication Processor Module
MOTOROLA
MPC823e REFERENCE MANUAL
16-167
SCCs
COMMUNICATION
16
PROCESSOR MODULE
TCRC—Transparent CRC (Totally Transparent Mode Only)
This field selects the type of frame checking that is provided on the transparent channels of
a serial communication controller (either the receiver, transmitter, or both, as defined by the
TTX and TRX bits). Although this configuration selects a frame check type, the actual
decision to send the frame check is made in the TX buffer descriptor. Thus, it is not required
to send a frame check in transparent mode. If a frame check is not used, you can simply
ignore the frame check errors that are generated on the receiver.
00 = 16-bit CCITT CRC (HDLC). (X16 + X12 + X5 + 1).
01 = CRC16. (X16 + X15 + X2 + 1).
10 = 32-bit CCITT CRC (Ethernet, HDLC, and High-Speed IrDA).
(X32 + X26 + X23 + X22 + X16 + X12 + X11 + X10 + X8 + X7 + X5 + X4 + X2 +
X1 +1). Also called CRC32.
11 = Reserved.
REVD—Reverse Data (Transparent Mode Only)
0 = Normal operation.
1 = When set, this bit causes the totally transparent channels on the serial
communication controller (either the receiver, transmitter, or both) to reverse the
bit order and transmit the MSB of each octet first.
TRX—Transparent Receiver
The serial communication controllers offer totally transparent operation. However, to
increase flexibility, totally transparent operation is not configured with the MODE field of the
GSMR_L, but with the TTX and TRX bits. This gives you the opportunity to implement
unique applications, such as configuring an SCCx transmitter for UART operation and
configuring the receiver for totally transparent operation. This can be done by setting the
MODE field to UART, TTX to 0, and TRX to 1.
0 = Normal operation.
1 = The receiver operates in totally transparent mode, regardless of the protocol
selected for the transmitter in the MODE field of the GSMR_L.
Note:
Full-duplex transparent operation for a serial communication controller is
obtained by setting the TTX and TRX bits. The serial communication controllers
cannot operate with Ethernet on the transmitter or while transparent operation is
on the receiver. In other words, if the MODE field is set for Ethernet, then TTX
must equal TRX or erratic operation will occur.
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