MC68HC908GR4MP datasheet(162/286 Pages) FREESCALE

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Serial Communications Interface (SCI)

MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7

162

Freescale Semiconductor

18.3 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 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 chapter.

18.4 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).

Table 18-1. Pin Name Conventions

Generic Pin Names:

RxD

TxD

Full Pin Names:

PE1/RxD

PE0/TxD

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