MC68HC08AZ16 Datasheet, PDF (236/527 Pages) Motorola, Inc – HCMOS Microcontroller Unit

MOSI (Master
out/Slave in)
Serial Peripheral Interface Module (SPI)
I/O Signals
MOSI is one of the two SPI module pins that transmits serial data. In full
duplex operation, the MOSI pin of the master SPI module is connected
to the MOSI pin of the slave SPI module. The master SPI simultaneously
transmits data from its MOSI pin and receives data on its MISO pin.
When enabled, the SPI controls data direction of the MOSI pin
regardless of the state of the data direction register of the shared I/O
port.
SPSCK (serial
clock)
The serial clock synchronizes data transmission between master and
slave devices. In a master MCU, the SPSCK pin is the clock output. In a
slave MCU, the SPSCK pin is the clock input. In full duplex operation,
the master and slave MCUs exchange a byte of data in eight serial clock
cycles.
When enabled, the SPI controls data direction of the SPSCK pin
regardless of the state of the data direction register of the shared I/O
port.
SS (slave select)
The SS pin has various functions depending on the current state of the
SPI. For an SPI configured as a slave, the SS is used to select a slave.
For CPHA = ’0’, the SS is used to define the start of a transmission. See
Transmission formats on page 217. Since it is used to indicate the start
of a transmission, the SS must be toggled high and low between each
byte transmitted for the CPHA = ‘0’ format. However, it can remain low
throughout the transmission for the CPHA = ‘1’ format. See Figure 12.
MISO/MOSI
MASTER SS
SLAVE SS
(CPHA =’0’)
SLAVE SS
(CPHA = ’1’)
BYTE 1
BYTE 2
BYTE 3
Figure 12. CPHA/SS timing
27-spi
MOTOROLA
Serial Peripheral Interface Module (SPI)
MC68HC08AZ32
235