Motorola DSP56305 User Manual page 267

Enhanced Synchronous Serial Interface (ESSI)
ESSI Data and Control Signals
If SC0 is an output, this signal can be configured as either serial output flag 0 or a
Receive Shift Register clock output. If SC0 is an input, this signal may be used either as
serial input flag 0 or as a Receive Shift Register clock input. If SC0 is used as serial input
flag 0, it controls the state of serial Input Flag 0 (IF0) bit in the ESSI Status Register
(SSISR).
When SC0 is configured as a transmit data signal, it is always an output signal regardless
of the SCD0 bit value. SC0 is fully synchronized with the other transmit data signals
(STD and SC1).
SC0 may be programmed as a GPIO signal (P0) when the ESSI SC0 function is not being
used.
Note: The ESSI can operate with more than one active transmitter only in
Synchronous mode.
MOTOROLA DSP56305 User's Manual 7-9