MPC823 datasheet(15/74 Pages) MOTOROLA

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Communication Processor Module

MOTOROLA

MPC823 REFERENCE MANUAL

16-393

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.

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