Motorola MPC823e Reference Manual page 762

Communication Processor Module
• GRACEFUL STOP TRANSMIT—This command is used to stop transmission
smoothly, rather than abruptly, in much the same way that the regular STOP
TRANSMIT command stops. It stops transmission after the current frame finishes or
immediately if there is no frame being transmitted. A transparent frame is not complete
until a buffer descriptor with the L bit set has its associated buffer completely
transmitted. The GRA bit in the SCCE–Transparent register is set once transmission
stops and then the transmit parameters and their buffer descriptors can be modified.
The TBPTR points to the next TX buffer descriptor in the table. Transmission begins
once the R bit of the next buffer descriptor is set and the RESTART TRANSMIT
command is issued.
• RESTART TRANSMIT—This command reenables the transmission of characters on
the transmit channel. The SCCx Transparent controller expects it after a STOP
TRANSMIT command is issued, after a GRACEFUL STOP TRANSMIT command is
issued, or after a transmitter error occurs. The SCCx Transparent controller resumes
transmission from the current TBPTR in the channel TX buffer descriptor table.
• INIT TX PARAMETERS—This command initializes all transmit parameters in the serial
channel parameter RAM to their reset state. It must only be issued when the transmitter
is disabled. The INIT TX AND RX PARAMS command can also be used to reset the
transmit and receive parameters.
You can program the CPM command register with the following commands to receive data.
See Section 16.2.6.1 CPM Command Register for additional information.
• ENTER HUNT MODE—After the hardware or software is reset and the channel is
enabled in the GSMR_H, the channel is in receive enable mode and uses the first buffer
descriptor in the table. This command is used to force the transparent receiver to stop
receiving the current frame and enter hunt mode where the SCCx Transparent
controller is waiting for the synchronization sequence. After receiving the command, the
current receive buffer is closed. Further data reception uses the next buffer descriptor.
• CLOSE RX BD—This command is used to force a serial communication controller to
close the RX buffer descriptor if it is currently being used and to use the next buffer
descriptor for any subsequently received data. If a serial communication controller is
not in the process of receiving data, no action is taken by this command.
• INIT RX PARAMETERS—This command initializes all the receive parameters in this
serial channel parameter RAM to their reset state and must only be issued when the
receiver is disabled. The INIT TX AND RX PARAMS command can also be used to
reset the receive and transmit parameters.
16-308 MPC823e REFERENCE MANUAL MOTOROLA