Signal/Connection Descriptions
Serial Host Interface (SHI)
MOTOROLA
DSP56007/D
1-11
MISO
SDA
Input or
Output
Input or
Output
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.
I
2
C Serial Data and Acknowledge (SDA)
—In I
2
C mode,
SDA is a Schmitt-trigger input when receiving and an
open-drain output when transmitting. SDA should be
connected to V
CC
through a pull-up resistor. SDA carries
the data for I
2
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).
MOSI
HA0
Input or
Output
Input
Tri-stated
SPI Master-Out-Slave-In (MOSI)
—When the SPI is
configured as a master, MOSI is the master data output
line. The MOSI signal is used in conjunction with the
MISO signal for transmitting and receiving serial data.
MOSI is the slave data input line when the SPI is
configured as a slave. This signal is a Schmitt-trigger
input when configured for the SPI Slave mode.
I
2
C Slave Address 0 (HA0)—
This signal uses a Schmitt-
trigger input when configured for the I
2
C mode. When
configured for I
2
C Slave mode, the HA0 signal is used to
form the slave device address. HA0 is ignored when the
SHI is configured for the I
2
C Master mode.
Note:
This signal is tri-stated during hardware reset,
software reset, or individual reset (no need for
external pull-up in this state).
Table 1-8
Serial Host Interface (SHI) signals (Continued)
Signal Name
Signal
Type
State
during
Reset
Signal Description