Freescale Semiconductor, Inc.
Serial Communications Interface (SCI)
The SCI shares I/O with two of port D’s pins:
Alternate
Pin
function
PD0
PD1
RXD1
TXD1
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.
Transmitter
Internal
phase 2 clock
baud rate
ST4XCK
13-bit counter
clock
÷ 16
Reset
EQ
Sync
13-bit compare
÷ 2
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
MC68HC11P2 — Rev 1.0
Serial Communications Interface (SCI)
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