MC908JB16DWE Datasheet, PDF (210/332 Pages) Freescale Semiconductor, Inc – Microcontrollers

Serial Communications Interface
12.4 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 12-1 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 12-1. Pin Name Conventions
Generic Pin Names:
RxD
Full Pin Names:
PTC1/RxD
TxD
PTC0/TxD
12.5 Functional Description
Figure 12-1 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 is the OSCDCLK from the
oscillator circuit, which is two times the crystal clock, OSCXCLK.
Technical Data
210
Serial Communications Interface Module (SCI)
MC68HC908JB16 — Rev. 1.1
Freescale Semiconductor