Motorola MPC8260 - Manual (Page 705)

MOTOROLA Chapter 26. Serial Management Controllers (SMCs) 26-9
Part IV. Communications Processor Module
26.2.4 Disabling SMCs On-the-Fly
An SMC can be disabled and reenabled later by ensuring that buffers are closed properly
and new data is transferred to or from a new buffer. Such a sequence is required if the
parameters to be changed are not dynamic. If the register or bit description states that
dynamic changes are allowed, the sequences need not be followed and the register or bits
may be changed immediately.
Note that the SMC does not have to be fully disabled for parameter RAM to be modiÞed.
Table 26-2 describes when parameter RAM values can be modiÞed. To disable all SCCs,
SMCs, the SPI, and the I
2
C, use the CPCR to reset the CPM with a single command.
26.2.4.1 SMC Transmitter Full Sequence
Follow these steps to fully enable or disable the SMC transmitter:
1. If the SMC is sending data, issue a STOP TRANSMIT command to stop transmission
smoothly. If the SMC is not sending, if TBPTR is overwritten, or if an INIT TX
PARAMETERS command is executed, this command is not required.
2. Clear SMCMR[TEN] to disable the SMC transmitter and put it in reset state.
3. Update SMC transmit parameters, including the parameter RAM. To switch
protocols or reinitialize parameters, issue an INIT TX PARAMETERS command.
4. Issue a RESTART TRANSMIT if an INIT TX PARAMETERS was issued in step 3.
5. Set SMCMR[TEN]. Transmission now begins using the TxBD that the TBPTR
value pointed to as soon as the R bit is set in the TxBD.
26.2.4.2 SMC Transmitter Shortcut Sequence
This shorter sequence reinitializes transmit parameters to the state they had after reset.
1. Clear SMCMR[TEN].
2. Issue an
INIT TX PARAMETERS command and make any additional changes.
3. Set SMCMR[TEN].
26.2.4.3 SMC Receiver Full Sequence
Follow these steps to fully enable or disable the receiver:
1. Clear SMCMR[REN]. Reception is aborted immediately, which disables the SMC
receiver and puts it in a reset state.
2. Modify SMC receive parameters, including parameter RAM. To switch protocols or
reinitialize SMC receive parameters, issue an INIT RX PARAMETERS command.
3. Issue a CLOSE RXBD command if INIT RX PARAMETERS was not issued in step 2.
4. Set SMCMR[REN]. Reception immediately uses the RxBD that RBPTR pointed to
if E is set in the RxBD.