MC68HC812A4 Datasheet, PDF (279/342 Pages) Motorola, Inc – 16-bit device composed of standard on-chip peripheral modules connected by an intermodule bus. Modules include

Serial Peripheral Interface (SPI)
External Pins
15.8 External Pins
The SPI module has four I/O pins:
• MISO — Master data in, slave data out
• MOSI — Master data out, slave data in
• SCK — Serial clock
• SS — Slave select
The SPI has limited inter-integrated circuit (I²C) capability (requiring
software support) as a master in a single-master environment. To
communicate with I²C peripherals, MOSI becomes an open-drain output
when the SWOM bit in the SPI control register is set. In I²C
communication, the MOSI and MISO pins are connected to a
bidirectional pin from the I²C peripheral and through a pullup resistor to
V_DD.
15.8.1 MISO (Master In, Slave Out)
In a master SPI, MISO is the data input. In a slave SPI, MISO is the data
output.
In a slave SPI, the MISO output pin is enabled only when its SS pin is at
logic 0. To support a multiple-slave system, a logic 1 on the SS pin of a
slave puts the MISO pin in a high-impedance state.
15.8.2 MOSI (Master Out, Slave In)
In a master SPI, MOSI is the data output. In a slave SPI, MOSI is the
data input.
15.8.3 SCK (Serial Clock)
The serial clock synchronizes data transmission between master and
slave devices. In a master SPI, the SCK pin is the clock output to the
slave. In a slave MCU, the SCK pin is the clock input from the master.
Advance Information
MOTOROLA
Serial Peripheral Interface (SPI)
MC68HC812A4 — Rev. 3.0
279