
Serial Communications Interface (SCI)
Pin Name Conventions
MC68HC08AS32A — Rev. 1
Data Sheet
MOTOROLA
Serial Communications Interface (SCI)
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13.3 Pin Name Conventions
The generic names of the SCI I/O pins are:
RxD (receive data)
TxD (transmit data)
SCI I/O (input/output) lines are implemented by sharing parallel I/O port pins. The
full name of an SCI input or output reflects the name of the shared port pin.
Table 13-1
shows the full names and the generic names of the SCI I/O pins.
The generic pin names appear in the text of this section.
13.4 Functional Description
Figure 13-3
shows the structure of the SCI module. The SCI allows full-duplex,
asynchronous, NRZ serial communication among the MCU and remote devices,
including other MCUs. The transmitter and receiver of the SCI operate
independently, although they use the same baud rate generator. During normal
operation, the CPU monitors the status of the SCI, writes the data to be
transmitted, and processes received data.
The baud rate clock source for the SCI can be selected via the configuration bit,
SCIBDSRC, of the MOR2 register ($001E). Source selection values are shown in
Figure 13-3
.
13.4.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format illustrated
in
Figure 13-2
.
Figure 13-2. SCI Data Formats
Table 13-1. Pin Name Conventions
Generic Pin Names:
RxD
TxD
Full Pin Names:
PTE1/RxD
PTE0/TxD
BIT 5
START
BIT
BIT 0
BIT 1
NEXT
START
BIT
STOP
BIT
8-BIT DATA FORMAT
BIT M IN SCC1 CLEAR
START
BIT
BIT 0
NEXT
START
BIT
STOP
BIT
9-BIT DATA FORMAT
BIT M IN SCC1 SET
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 2
BIT 3
BIT 4
BIT 6
BIT 7
PARITY
BIT
PARITY
BIT
F
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