MC68HC812A4 Datasheet, PDF (229/342 Pages) Motorola, Inc – 16-bit device composed of standard on-chip peripheral modules connected by an intermodule bus. Modules include

Serial Communications Interface Module (SCI)
Functional Description
14.6 Functional Description
The SCI allows full-duplex, asynchronous, NRZ serial communication
between the MCU and remote devices, including other MCUs. The SCI
transmitter and receiver operate independently, although they use the
same baud rate generator. The CPU monitors the status of the SCI,
writes the data to be transmitted, and processes received data.
14.6.1 Data Format
The SCI uses the standard NRZ mark/space data format illustrated in
Figure 14-3.
Advance Information
MOTOROLA
START
BIT BIT 0
BIT 1
BIT 2
8-BIT DATA FORMAT
BIT M IN SCCR1 CLEAR
PARITY
OR DATA
BIT
BIT 3 BIT 4 BIT 5 BIT 6 BIT 7 STOP
BIT
NEXT
START
BIT
9-BIT DATA FORMAT
PARITY
BIT M IN SCCR1 SET
OR DATA
BIT
NEXT
START
START
BIT BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 BIT 7 BIT 8 STOP BIT
BIT
Figure 14-3. SCI Data Formats
Each data character is contained in a frame that includes a start bit, eight
or nine data bits, and a stop bit. Clearing the M bit in SCI control register
1 configures the SCI for 8-bit data characters. A frame with eight data
bits has a total of 10 bits. Setting the M bit configures the SCI for 9-bit
data characters. A frame with nine data bits has a total of 11 bits.
Table 14-1. Example 8-Bit Data Formats
Start Bit Data Bits Address Bit Parity Bit Stop Bit
1
8
0
0
1
1
7
0
2
1
7
0
1
1
1
7
1⁽¹⁾
1
1. The address bit identifies the frame as an address character. See 14.6.4.6
Receiver Wakeup.
Serial Communications Interface Module (SCI)
MC68HC812A4 — Rev. 3.0
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