Motorola DSP56009 User Manual page 53

Table 2-8 Serial Host Interface (SHI) signals (Continued)
Signal
Signal Name
Type
MISO Input or
Output
SDA Input or
Output
MOTOROLA
State
during
Reset
Tri-stated SPI Master-In-Slave-Out (MISO)— When the SPI
is configured as a master, MISO is the master data
input line. The MISO signal is used in conjunction
with the MOSI signal for transmitting and
receiving serial data. This signal is a
Schmitt-trigger input when configured for the SPI
Master mode, an output when configured for the
SPI Slave mode, and tri-stated if configured for the
SPI Slave mode when SS is deasserted.
2
I C Serial Data and Acknowledge (SDA)—In I
mode, SDA is a Schmitt-trigger input when
receiving and an open-drain output when
transmitting. SDA should be connected to V
through a pull-up resistor. SDA carries the data for
2
I C transactions. The data in SDA must be stable
during the high period of SCL. The data in SDA is
only allowed to change when SCL is low. When
the bus is free, SDA is high. The SDA line is only
allowed to change during the time SCL is high in
the case of Start and Stop events. A high-to-low
transition of the SDA line while SCL is high is an
unique situation, and is defined as the Start event.
A low-to-high transition of SDA while SCL is high
is an unique situation, and is defined as the Stop
event.
Note: This line is tri-stated during hardware reset,
software reset, or individual reset (no need for
external pull-up in this state).
DSP56009 User's Manual
Signal Descriptions
Serial Host Interface (SHI)
Signal Description
2
C
CC
2-15