SYNCHRONOUS SERIAL INTERFACE (SSI)
MOTOROLA
PORT C
6 - 83
Table 6-8 SSI Operation: Flag 1 and Rx Frame Sync
6.4.1.6
Serial Control Pin (SC2)
This pin is used for frame sync I/O (see Table 6-5 and Table 6-9). SC2 is the frame sync for
both the transmitter and receiver in synchronous mode and for the transmitter only in asyn-
chronous mode. The direction of this pin is determined by the SCD2 bit in CRB. When config-
ured as an output, this pin is the internally generated frame sync signal. When configured as
an input, this pin receives an external frame sync signal for the transmitter (and the receiver
in synchronous operation). In the gated clock mode, external frame sync signals are not used.
Table 6-9 SSI Operation: Tx and Rx Frame Sync
6.4.2
SSI Programming Model
The SSI can be viewed as two control registers, one status register, a transmit register, a
receive register, and special-purpose time slot register. These registers are illustrated in
Figure 6-44 and Figure 6-45. The following paragraphs give detailed descriptions and op-
erations of each of the bits in the SSI registers. The SSI registers are not prefaced with
an “S” (for serial) as are the SCI registers.
SYN
GCK
SCD1
Operation
Synchronous
Continuous
Input
Flag 1 Input
Synchronous
Continuous
Output
Flag 1 Output
Synchronous
Gated
Input
Flag 1 Input
Synchronous
Gated
Output
Flag 1 Output
Asynchronous
Continuous
Input
RX Frame Sync – External
Asynchronous
Continuous
Output
RX Frame Sync – Internal
Asynchronous
Gated
Input
–
Asynchronous
Gated
Output
RX Frame Sync – Internal
SYN
GCK
SCD2
Operation
Synchronous
Continuous
Input
TX and RX Frame Sync
Synchronous
Continuous
Output
TX and RX Frame Sync
Synchronous
Gated
Input
–
Synchronous
Gated
Output
TX and RX Frame Sync
Asynchronous
Continuous
Input
TX Frame Sync – External
Asynchronous
Continuous
Output
TX Frame Sync – Internal
Asynchronous
Gated
Input
–
Asynchronous
Gated
Output
TX Frame Sync – Internal
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Freescale Semiconductor, Inc.
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