MC68HC05C8A Datasheet, PDF (59/116 Pages) Motorola, Inc – Microcontrollers

Chapter 10
Serial Peripheral Interface (SPI)
10.1 Introduction
The serial peripheral interface (SPI) is an interface built into the MC68HC05 microcontroller unit (MCU)
which allows several MC68HC05 MCUs or MC68HC05 MCU plus peripheral devices to be interconnected
within a single printed circuit board. In an SPI, separate wires are required for data and clock. In the SPI
format, the clock is not included in the data stream and must be furnished as a separate signal. An SPI
system may be configured in a system containing one master MCU and several slave MCUs or in a
system in which an MCU is capble of being a master or a slave.
10.2 Features
Features include:
• Full duplex, 4-wire synchronous transfers
• Master or slave operation
• Bus frequency divided by 2 (maximum) master bit frequency
• Bus frequency (maximum) slave bit frequency
• Four programmable master bit rates
• Programmable clock polarity and phase
• End-of-transmission interrupt flag
• Write collision flag protection
• Master-master mode fault protection capability
10.3 SPI Signal Description
The four basic signals (MOSI, MISO, SCK, and SS) are described in this subsection. Each signal function
is described for both the master and slave mode.
10.3.1 Master In Slave Out (MISO)
The MISO line is configured as an input in a master device and as an output in a slave device. It is one
of the two lines that transfer serial data in one direction, with the most significant bit sent first. The MISO
line of a slave device is placed in the high-impedance state if the slave is not selected.
10.3.2 Master Out Slave In (MOSI)
The MOSI line is configured as an output in a master device and as an input in a slave device. It is one
of the two lines that transfer serial data in one direction with the most significant bit sent first.
MC68HC05C8A • MC68HCL05C8A • MC68HSC05C8A Data Sheet, Rev. 5.1
Freescale Semiconductor
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