beautypg.com

4 serial control signal (sc0), 5 serial control signal (sc1), Serial control signal (sc0) -4 – Motorola DSP56301 User Manual

Page 202: Serial control signal (sc1) -4

background image

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.