MC68HC(7)05H12
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Rev. 1.0
General Release Specification
MOTOROLA
Serial Communications Interface (SCI)
125
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General Release Specification — MC68HC(7)05H12
Section 11. Serial Communications Interface (SCI)
11.1 Contents
11.2
11.3
11.4
11.4.1
11.4.2
11.5
11.6
11.7
11.8
11.8.1
11.8.2
11.8.3
11.8.4
11.8.5
11.9
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .130
Receiver Wake-up Operation . . . . . . . . . . . . . . . . . . . . . . . . .130
Idle Line Wake-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131
Address Mark Wake-up. . . . . . . . . . . . . . . . . . . . . . . . . . .131
Receive Data (RDI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132
Start Bit Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132
Transmit Data (TDO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135
Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135
Serial Communications Data Register (SCDAT). . . . . . . .135
Serial Communications Control Register 1 (SCCR1) . . . .136
Serial Communications Control Register 2 (SCCR2) . . . .137
Serial Communications Status Register (SCSR) . . . . . . .138
Baud Rate Register (BAUD) . . . . . . . . . . . . . . . . . . . . . . .140
SCI During WAIT Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142
11.2 Introduction
The SCI is a full-duplex UART-type asynchronous system, using
standard non return-to-zero (NRZ) format (one start bit, eight or nine
data bits, and a stop bit). An on-chip baud-rate generator derives
standard baud-rate frequencies from the MCU oscillator. Both the
transmitter and the receiver are double buffered; thus, back-to-back
characters can be handled easily, even if the central processing unit
(CPU) is delayed in responding to the completion of an individual
character. The SCI transmitter and receiver are functionally independent
but use the same format and baud rate.