Motorola MPC8260 User Manual

26-10

MOTOROLA

This shorter sequence reinitializes receive parameters to their state after reset. 

1. Clear SMCMR[REN].
2. Issue an 

INIT

 

RX

 

PARAMETERS

 command and make any additional changes.

3. Set SMCMR[REN].

To switch the protocol that the SMC is executing without resetting the board or affecting
any other SMC, use one command and follow these steps:

1. Clear SMCMR[REN] and SMCMR[TEN].
2. Issue an 

INIT

 

TX

 

AND

 

RX

 

PARAMETERS

 

COMMAND

 to initialize transmit and receive 

parameters. Make any additional SMCMR changes. 

3. Set SMCMR[REN, TEN]. The SMC is now enabled with the new protocol.

When SMCMR[TEN, REN] are cleared, the SMC consumes little power.

Follow these steps to handle an interrupt in the SMC:

1. Once an interrupt occurs, read SMCE to identify the interrupt source. The SMCE 

bits are usually cleared at this time.

2. Process the TxBD to reuse it if SMCE[TXB] is set. Extract data from the RxBD if 

SMCE[RXB] is set. To send another buffer, set TxBD[R].

3. Execute the rÞ instruction.

SMCs generally offer less functionality and performance in UART mode than do SCCs,
which makes them more suitable for simpler debug/monitor ports instead of full-featured
UARTs. SMCs do not support the following features in UART mode.

¥

RTS, CTS, and CD signals

¥

Receive and transmit sections clocked at different rates

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Fractional stop bits

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Built-in multidrop modes

¥

Freeze mode for implementing flow control

¥

Isochronous operation (1

´ clock)

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Interrupts on special control character reception

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Ability to transmit data on demand using the TODR

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SCCS register to determine idle status of the receive signal

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Other features for the SCCs as described in the GSMR