MC908GR8CDWE Datasheet, PDF (233/408 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Freescale Semiconductor, Inc.
Serial Communications Interface (SCI)
Pin Name Conventions
18.4 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 18-1 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.
Table 18-1. Pin Name Conventions
Generic Pin Names:
Full Pin Names:
RxD
PE1/RxD
TxD
PE0/TxD
18.5 Functional Description
Figure 18-1 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 CONFIG2 register ($001E). Source
selection values are shown in Figure 18-1.
MC68HC908GR8 — Rev 4.0
MOTOROLA
Serial Communications Interface (SCI)
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Technical Data
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