MC68HC908GR8A_07 Datasheet, PDF (133/260 Pages) Freescale Semiconductor, Inc – Microcontrollers

Pin Name Conventions
13.3 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 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 13-3 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 13-3.
13.4.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format illustrated in Figure 13-2.
8-BIT DATA FORMAT
BIT M IN SCC1 CLEAR
PARITY
BIT
NEXT
START
START
BIT BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 BIT 7 ^STOP BIT
BIT
START
9-BIT DATA FORMAT
BIT M IN SCC1 SET
PARITY
BIT
NEXT
START
BIT BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 BIT 7 BIT 8 STOP BIT
BIT
Figure 13-2. SCI Data Formats
MC68HC908GR8A • MC68HC908GR4A Data Sheet, Rev. 5
Freescale Semiconductor
133