Motorola DSP56305 User Manual page 92

Signal/Connection Descriptions
Enhanced Synchronous Serial Interface 1 (ESSI1)
Table 2-12 Enhanced Synchronous Serial Interface 1 (ESSI1) (Continued)
Signal
Type
Name
SCK1 Input/
Output
PD3 Input
or
Output
SRD1 Input/
Output
PD4 Input
or
Output
2-34
State During
Reset Stop
Input Disconnected
Input Disconnected
DSP56305 User's Manual
Signal Description
Serial Clock—SCK1 is a bidirectional
Schmitt-trigger input signal providing the serial
bit rate clock for the ESSI. The SCK1 is a clock
input or output used by both the transmitter
and receiver in Synchronous modes, or by the
transmitter in Asynchronous modes.
Although an external serial clock can be
independent of and asynchronous to the DSP
system clock, it must exceed the minimum clock
cycle time of 6 T (i.e., the system clock
frequency must be at least three times the
external ESSI clock frequency). The ESSI needs
at least three DSP phases inside each half of the
serial clock.
Port D 3—The default configuration following
reset is GPIO input PD3. When configured as
PD3, signal direction is controlled through
PRR1. The signal can be configured as an ESSI
signal SCK1 through PCR1.
This input is 5 V tolerant.
Serial Receive Data—SRD1 receives serial data
and transfers the data to the ESSI receive shift
register. SRD1 is an input when data is being
received.
Port D 4—The default configuration following
reset is GPIO input PD4. When configured as
PD4, signal direction is controlled through
PRR1. The signal can be configured as an ESSI
signal SRD1 through PCR1.
This input is 5 V tolerant.
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