Motorola DSP56301 - Manual (Page 202)

ESSI Data and Control Signals
7 -4 DSP56301 User’s Manual
7.2.4 Serial Control Signal (SC0)
ESSI0: SC00; ESSI1: SC10
To determine the function of the SC0 signal, select either Synchronous or Asynchronous
mode, according to Table 7-2. In Asynchronous mode, this signal is used for the receive
clock I/O. In Synchronous mode, this signal is the transmitter data out signal for transmit shift
register TX1 or for serial flag I/O. A typical application of serial flag I/O would be multiple
device selection for addressing in codec systems.
If SC0 is configured as a serial flag signal or receive clock signal, its direction is determined
by the Serial Control Direction 0 (SCD0) bit in ESSI Control Register B (CRB). When
configured as an output,
SC0 functions as the serial Output Flag 0 (OF0) or as a receive shift
register clock output. If SC0 is used as the serial Output Flag 0, its value is determined by the
value of the serial Output Flag 0 (OF0) bit in the CRB. If SC0 is an input, it functions as either
serial Input Flag 0 or a receive shift register clock input. As serial Input Flag 0, SC0 controls
the state of the 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 can be programmed as a GPIO signal ( P0 ) when the ESSI SC0 function is not in
use.
Note: The ESSI can operate with more than one active transmitter only in Synchronous
mode.
7.2.5 Serial Control Signal (SC1)
ESSI0:SC01; ESSI1: SCI11
To determine the function of SC1 , select either Synchronous or Asynchronous mode,
according to Table 7-2. In Asynchronous mode (as for a single codec with asynchronous
transmit and receive),
SC1 is the receiver frame sync I/O. In Synchronous mode, SC1 is the
transmitter data out signal of transmit shift register TX2, for the transmitter 0 drive-enabled
signal, or for serial flag I/O. As serial flag I/O,
SC1 operates like SC0 . SC0 and SC1are
independent flags but can be used together for multiple serial device selection; they can be
unencoded to select up to two CODECs or decoded externally to select up to four CODECs. If
SC1 is configured as a serial flag or receive frame sync signal, the Serial Control Direction 1
CRB[SCD1] bit determines its direction.