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Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SYNCHRONOUS SERIAL INTERFACE (SSI)

6.4.1.4Serial Control Pin (SC0)

The function of this pin is determined solely on the selection of either synchronous or asynchronous mode (see Table 6-5 and Table 6-6). For asynchronous mode, this pin will be used for the receive clock I/O. For synchronous mode, this pin is used for serial flag I/O. A typical application of flag I/O would be multiple device selection for addressing in codec systems. The direction of this pin is determined by the SCD0 bit in the CRB as described in Table 6-7. When configured as an output, this pin will be either serial output flag 0, based on control bit OF0 in CRB, or a receive shift register clock output. When configured as an input, this pin may be used either as serial input flag 0, which will control status bit IF0 in the SSISR, or as a receive shift register clock input.

Table 6-7 SSI Operation: Flag 0 and Rx Clock

 

 

 

 

 

 

 

SYN

GCK

SCD0

Operation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Synchronous

Continuous

Input

Flag 0 Input

 

 

 

 

 

 

 

 

Synchronous

Continuous

Output

Flag 0 Output

 

 

 

 

 

 

 

 

Synchronous

Gated

Input

Flag 0 Input

 

 

 

 

 

 

 

 

Synchronous

Gated

Output

Flag 0 Output

 

 

 

 

 

 

 

 

Asynchronous

Continuous

Input

Rx Clock – External

 

 

 

 

 

 

 

 

Asynchronous

Continuous

Output

Rx Clock – Internal

 

 

 

 

 

 

 

 

Asynchronous

Gated

Input

Rx Clock – External

 

 

 

 

 

 

 

 

Asynchronous

Gated

Output

Rx Clock – Internal

 

 

 

 

 

 

 

 

 

 

 

 

 

6.4.1.5Serial Control Pin (SC1)

The function of this pin is determined solely on the selection of either synchronous or asynchronous mode (see Table 6-5 and Table 6-8). In asynchronous mode (such as a single codec with asynchronous transmit and receive), this pin is the receiver frame sync I/O.

For synchronous mode with continuous clock, this pin is serial flag SC1 and operates like the previously described SC0. SC0 and SC1 are independent serial I/O flags but may be used together for multiple serial device selection. SC0 and SC1 can be used unencoded to select up to two codecs or may be decoded externally to select up to four codecs. The direction of this pin is determined by the SCD1 bit in the CRB. When configured as an output, this pin will be either a serial output flag, based on control bit OF1, or it will make the receive frame sync signal available. When configured as an input, this pin may be used as a serial input flag, which will control status bit IF1 in the SSI status register, or as a receive frame sync from an external source for continuous clock mode. In the gated clock mode, external frame sync signals are not used.

6 - 82 PORT C MOTOROLA

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