Motorola MPC8260 User Manual

26-20

MOTOROLA

9. Write MAX_IDL with 0x0000 in the SMC UART-speciÞc parameter RAM to 

disable the MAX_IDL functionality for this example.

10. Clear BRKLN and BRKEC in the SMC UART-speciÞc parameter RAM. 

11. Set BRKCR to 0x0001; if a 

STOP

 

TRANSMIT

 

COMMAND

 is issued, one break 

character is sent.

12. Initialize the RxBD. Assume the Rx data buffer is at 0x0000_1000 in main memory. 

Write 0xB000 to RxBD[Status and Control], 0x0000 to RxBD[Data Length] (not 
required), and 0x0000_1000 to RxBD[Buffer Pointer].

13. Assuming the Tx data buffer is at 0x0000_2000 in main memory and contains Þve 

8-bit characters, write 0xB000 to TxBD[Status and Control], 0x0005 to TxBD[Data 
Length], and 0x0000_2000 to TxBD[Buffer Pointer].

14. Write 0xFF to the SMCE1 register to clear any previous events.

15. Write 0x57 to the SMCM1 register to enable all possible SMC1 interrupts.

16. Write 0x0000_1000 to the SIU interrupt mask register low (SIMR_L) so the SMC1 

can generate a system interrupt. Write 0xFFFF_FFFF to the SIU interrupt pending 
register low (SIPNR_L) to clear events.

17. Write 0x4820 to SMCMR to conÞgure normal operation (not loopback), 8-bit 

characters, no parity, 1 stop bit. The transmitter and receiver are not yet enabled.

18. Write 0x4823 to SMCMR to enable the SMC transmitter and receiver. This 

additional write ensures that the TEN and REN bits are enabled last.

After 5 bytes are sent, the TxBD is closed. The receive buffer closes after receiving 16
bytes. Subsequent data causes a busy (out-of-buffers) condition since only one RxBD is
ready.

Compared to the SCC in transparent mode, the SMCs generally offer less functionality,
which helps them provide simpler functions and slower speeds. Transparent mode is
selected by programming SMCMR[SM] to 0b10. Section 26.2.1, ÒSMC Mode Registers
(SMCMR1/SMCMR2)Ó describes other protocol-speciÞc bits in the SMCMR. The SMC in
transparent mode does not support the following features:

¥

Independent transmit and receive clocks, unless connected to a TDM channel of an 
SIx

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CRC generation and checking

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Full RTS, CTS, and CD signals (supports only one SMSYN signal) 

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Ability to transmit data on demand using the TODR

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Receiver/transmitter in transparent mode while executing another protocol

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4-, 8-, or 16-bit SYNC recognition

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Internal DPLL support