Datasheet

M68HC12B Family Data Sheet, Rev. 9.1

Freescale Semiconductor 191

Chapter 14

Serial Interface

14.1 Introduction

• The serial interface of the MCU consists of two independent serial input/output (I/O) subsystems:

• Serial communication interface (SCI)

• Serial peripheral interface (SPI)

Each serial pin shares function with the general-purpose port pins of port S. The SCI is an NRZ

(non-return to zero) type system that is compatible with standard RS-232 systems. The SCI system has

a single-wire operation mode which allows the unused pin to be available as general-purpose I/O. The

SPI subsystem, which is compatible with the M68HC11 SPI, includes new features such as SS

output

and bidirectional mode.

Figure 14-1. Serial Interface Block Diagram

SCI

I/O

SPI

DDRS/IOCTLR

PORT S I/O DRIVERS

SERIAL

INTERFACE

PS0

PS1

PS2

PS3

PS4

PS5

PS6

PS7

RxD

TxD

MISO/SISO

MOSI/MOMI

SCK

/SS

I/O