mc68hc908mr24 Freescale Semiconductor, Inc, mc68hc908mr24 Datasheet - Page 277

• Manufacturer Part Number: mc68hc908mr24
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

13.12.2 MOSI (Master Out/Slave In)
13.12.3 SPSCK (Serial Clock)
13.12.4 SS (Slave Select)
MC68HC908MR24 — Rev. 4.1
Freescale Semiconductor
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
13.6 Transmission
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
Serial Peripheral Interface Module (SPI)
Formats. Since it is used to indicate the start of a
Serial Peripheral Interface Module (SPI)
Figure
Advance Information
13-12.
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