SYNCHRONOUS SERIAL INTERFACE (SSI)
6 - 82
PORT C
MOTOROLA
6.4.1.4
Serial 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 de-
scribed 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 config-
ured 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
6.4.1.5
Serial 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 sin-
gle 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 out-
put, 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 re-
ceive frame sync from an external source for continuous clock mode. In the gated clock
mode, external frame sync signals are not used.
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
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Freescale Semiconductor, Inc.
For More Information On This Product,
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