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Communication Processor Module
16.11.6.6 SMCx UART COMMANDS. You can program the CPM command register
(CPCR) with the following commands to transmit data.
• STOP TRANSMIT—This command disables the transmission of characters on the
transmit channel. If the SMCx UART controller receives this command while
transmitting a message, it stops transmitting. The SMCx UART controller finishes
transmitting any data that has already been transferred to its FIFO and shift register and
then stops transmitting data. The TBPTR is not advanced when this command is
issued. The SMCx UART controller transmits a programmable number of break
sequences and then transmits idles. The number of break sequences, which can be
zero, must be written to the BRKCR entry before this command is issued to the SMCx
UART controller.
• RESTART TRANSMIT—This command enables characters to be transmitted on the
transmit channel. The SMCx UART controller expects it after disabling the channel in
its SMCMR and after issuing the STOP TRANSMIT command. The SMCx UART
controller resumes transmission from the current TBPTR in the channel's transmit
buffer descriptor table.
• INIT TX PARAMETERS—This command initializes all the transmit parameters in this
serial channel's parameter RAM to their reset state and 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 CPCR with the following commands to receive data.
• ENTER HUNT MODE—This command cannot be used for an SMCx UART channel.
Issue the CLOSE RX BD command instead.
• CLOSE RX BD—This command is used to force a serial management controller to
close the current receive buffer descriptor if it is currently being used and to use the next
buffer descriptor in the list for any subsequently received data. If a serial management
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. This command 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.
16.11.6.7 SENDING A BREAK. A break is an all-zeros character without stop bits and it is
sent by issuing the STOP TRANSMIT command. The SMCx UART controller finishes
transmitting any outstanding data and then sends a character with consecutive zeros. The
number of zero bits in this character is the sum of the character length, plus the number of
start, parity, and stop bits. The SMCx UART controller transmits a programmable number of
break characters according to the BRKCR entry and then reverts to idle or sends data if the
RESTART TRANSMIT command was issued before completion. When the break is
completed, the transmitter sends at least one idle character before transmitting any data to
guarantee recognition of a valid start bit.
16-396
MPC823e REFERENCE MANUAL
MOTOROLA
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