MC68HC708XL36 FREESCALE [Freescale Semiconductor, Inc], MC68HC708XL36 Datasheet - Page 226

• Manufacturer Part Number: MC68HC708XL36
• Description: HCMOS Microcontroller Unit
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

SPI
MOSI (Master
Out/Slave In)
SPSCK (Serial
Clock)
SS (Slave Select)
MC68HC708XL36
226
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.
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.
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
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 between transmissions for the CPHA = 1 format. See
When an SPI is configured as a slave, the SS pin is always configured
as an input. It cannot be used as a general-purpose I/O regardless of the
MASTER SS
MISO/MOSI
(CPHA = 0)
(CPHA = 1)
SLAVE SS
SLAVE SS
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
BYTE 1
Figure 13. CPHA/SS Timing
SPI
on page 208.) Since it is used to indicate the
BYTE 2
BYTE 3
Figure
MOTOROLA
13.
26-spi_c