MC68HC908GP32_08 Datasheet, PDF (132/266 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Serial Communications Interface Module (SCI)
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.
Table 13-1. Pin Name Conventions
Generic Pin Names:
Full Pin Names:
RxD
PTE1/RxD
TxD
PTE0/TxD
13.4 Functional Description
Figure 13-1 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 13-1.
MC68HC908GP32 Data Sheet, Rev. 10
132
Freescale Semiconductor