Communication Processor Module
16-168
MPC823e REFERENCE MANUAL
MOTOROLA
SCCs
COMMUNICATION
16
PROCESSOR MODULE
TTX—Transparent Transmitter
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 allows you to implement unique applications,
such as configuring an SCCx receiver for HDLC operation and configuring a transmitter for
totally transparent operation. This can be done by setting the MODE field to HDLC, TTX to
1 and TRX to 0.
0 = Normal operation.
1 = The transmitter operates in totally transparent mode, regardless of the protocol
selected for the receiver in the MODE field of the GSMR_L.
CDP—Carrier-Detect Pulse
This bit must be set if a serial communication controller is used in the time-slot assigner.
0 = Normal operation (envelope mode). The CDx
signal must envelope the frame.
Negating CDx
while receiving data causes a CDx lost error.
1 = Pulse mode. Once the CDx
signal is asserted, synchronization has been achieved
and further transitions of CDx
have no effect on reception.
CTSP—CTS Pulse
0 = Normal operation (envelope mode). The CTSx
signal must envelope the frame.
Negating CTSx
while transmitting data causes a CTSx lost error.
1 = Pulse mode. Once the CTSx
signal is asserted, synchronization has been
achieved and further transitions of CTSx
have no effect on transmission.
CDS—Carrier-Detect Sampling
0 = The CDx
signal is assumed to be asynchronous with the data. It is internally
synchronized by a serial communication controller and then data is received.
1 = The CDx
signal is assumed to be synchronous with the data, which speeds up
operation. In this mode, CDx
must transition while the receive clock is in the low
state. As soon as CDx
is low, data is received. This mode is especially useful when
connecting an MPC823e in transparent mode because it allows the RTSx
signal of
one MPC823e to be directly connected to the CDx
signal of another MPC823e.
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 receiver or while transparent operation is on
the transmitter. In other words, if the MODE field is set to Ethernet, then TTX
must equal TRX or erratic operation will occur.
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