Serial Communications Interface (SCI)
The SCI shares I/O with two of port D’s pins:
Alternate
function
RXD1
TXD1
Pin
PD0
PD1
The SCI transmit and receive functions are enabled by TE and RE
respectively, in SCCR2.
The SCI features enabled on this MCU include: 13-bit modulus
prescaler; idle line detect; receiver-active flag; transmitter and receiver
hardware parity. A block diagram of the enhanced baud rate generator
is shown in
Figure 5-1.
See
Table 5-1
for example baud rate control
values.
Internal
phase 2 clock
Reset
13-bit compare
EQ
ST4XCK
13-bit counter
Transmitter
baud rate
clock
÷
16
÷
2
Sync
Receiver
baud rate
clock
SCBDH/L:
SCI baud control
Figure 5-1. SCI baud rate generator circuit diagram
5.3 Data format
The serial data format requires the following conditions:
•
•
•
An idle-line condition before transmission or reception of a
message.
A start bit, logic zero, transmitted or received, that indicates the
start of each character.
Data that is transmitted and received least significant bit (LSB)
first.
Technical Data
88
Serial Communications Interface (SCI)
MC68HC11P2 — Rev 1.0
MOTOROLA
MOTOROLA [ MOTOROLA, INC ]
