MC68HC908GR8 Datasheet, PDF (162/286 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Serial Communications Interface (SCI)
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.
Table 18-1. Pin Name Conventions
Generic Pin Names:
Full Pin Names:
RxD
PE1/RxD
TxD
PE0/TxD
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).
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
162
Freescale Semiconductor