MPC823 datasheet(10/74 Pages) MOTOROLA

10 / 74 page

Communication Processor Module

16-388

MPC823 REFERENCE MANUAL

MOTOROLA

16.11.5.1 DISABLING THE ENTIRE SMCx TRANSMITTER. Follow these steps to fully

enable or disable the SMCx transmitter:

1. Issue the STOP TRANSMIT command. This command is recommended when a serial

management controller is transmitting data since it stops transmission smoothly. This

command is not required if a serial management controller is not transmitting, if you

overwrite the TBPTR or if you execute the INIT TX PARAMETERS command.

2. Clear the TEN bit in the SMCMR. This disables the SMCx transmitter and puts it in a

reset state.

3. Modify the SMCx transmit parameters, including the parameter RAM. If you prefer to

switch protocols or restore the SMCx transmit parameters to their initial state, issue

the INIT TX PARAMETERS command.

4. Issue the RESTART TRANSMIT command. You must do this if you did not issue the

INIT TX PARAMETERS command in step 3.

5. Set the TEN bit in the SMCMR. When the R bit is set in the TX buffer descriptor,

transmission begins using the TX buffer descriptor indicated by the TBPTR value.

16.11.5.2 DISABLING PART OF THE SMCx TRANSMITTER. Follow this shorter

sequence if you prefer to reinitialize the transmit parameters to the state they were in after

reset.

1. Clear the TEN bit in the SMCMR.

2. Issue the INIT TX PARAMETERS command and make any additional modifications.

3. Set the TEN bit in the SMCMR.

16.11.5.3 DISABLING THE ENTIRE SMCx RECEIVER. Follow these steps to fully enable

or disable the receiver:

1. Clear the REN bit in the SMCMR. Reception is aborted immediately, which disables

the SMCx receiver and puts it in a reset state.

2. Modify the SMCx receive parameters, including the parameter RAM. If you prefer to

switch protocols or restore the SMCx receive parameters to their initial state, issue the

INIT RX PARAMETERS command.

3. Issue the CLOSE RX BD command. You must do this if you did not issue the INIT RX

PARAMETERS command in step 2.

4. Set the REN bit in the SMCMR. When the E bit is set in the RX buffer descriptor,

reception begins immediately using the RX buffer descriptor indicated by the RBPTR.

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