MC68HC708MP16 Datasheet, PDF (273/398 Pages) Freescale Semiconductor, Inc – Microcontrollers

Serial Peripheral Interface Module (SPI)
13.13 I/O Signals
The SPI module has five I/O pins and shares four of them with a parallel
I/O port.
• MISO — Data received
• MOSI — Data transmitted
• SPSCK — Serial clock
• SS — Slave select
• CGND — Clock ground
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 SPWOM 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.
13.13.1 MISO (Master In/Slave Out)
MISO is one of the two SPI module pins that transmits serial data. In full
duplex operation, the MISO pin of the master SPI module is connected
to the MISO pin of the slave SPI module. The master SPI simultaneously
receives data on its MISO pin and transmits data from its MOSI pin.
Slave output data on the MISO pin is enabled only when the SPI is
configured as a slave. The SPI is configured as a slave when its
SPMSTR bit is logic 0 and its SS pin is at logic 0. To support a multiple-
slave system, a logic 1 on the SS pin puts the MISO pin in a high-
impedance state.
When enabled, the SPI controls data direction of the MISO pin
regardless of the state of the data direction register of the shared I/O
port.
MC68HC708MP16 — Rev. 3.1
Freescale Semiconductor
Serial Peripheral Interface Module (SPI)
Technical Data
273