Serial Control Signal (Sc1) - Motorola DSP56305 User Manual

Enhanced Synchronous Serial Interface (ESSI)
ESSI Data and Control Signals
7.3.5

Serial Control Signal (SC1)

In ESSI0:SC01; In ESSI1: SCI11
The function of this signal is determined by selecting either Synchronous or
Asynchronous mode (see Figure 7-4, Table 7-4, and Figure 7-15). In Asynchronous
mode (such as a single codec with asynchronous transmit and receive), SC1 is the
receiver frame sync I/O. In Synchronous mode, SC1 is used for the transmitter data out
signal of Transmit Shift Register TX2, for the drive enable transmitter 0 signal, or for
serial flag SC1.
When used as SC1, it operates like the previously described SC0. SC0 and SC1 are
independent 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. If SC1 is configured as a serial flag signal, its direction is
determined by the SCD1 bit in the CRB.
When configured as an output, SC1 functionality is determined by control bit OF1 in the
SSISR. The SC1 signal can be used as a serial output flag, the transmitter 0 drive enable
signal, or the receive frame sync signal output. When configured as an input, this signal
can be used as to receive frame sync signals from an external source or it can be used as a
serial input flag. When SC1 is a serial input flag, it controls status bit IF1 in the SSISR.
When this signal is configured as a transmit data signal, it is always an output signal
regardless of the SCD1 bit value. As an output, it is fully synchronized with the other
ESSI transmit data signals (STD and SC0). SC1 may be programmed as a GPIO signal
(P1) when the ESSI SC1 function is not being used.
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