SH7101 Datasheet, PDF (330/486 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

10. Serial Communication Interface (SCI)
10.4 Operation in Asynchronous Mode
Figure 10.2 shows the general format for asynchronous serial communication. One frame consists
of a start bit (low level), followed by data, a parity bit, and finally stop bits (high level). In
asynchronous serial communication, the transmission line is usually held in the mark state (high
level). The SCI monitors the communication line, and when it goes to the space state (low level),
recognizes a start bit and starts serial communication. Inside the SCI, the transmitter and receiver
are independent units, enabling full-duplex communication. Both the transmitter and the receiver
also have a double-buffered structure, so that data can be read or written during transmission or
reception, enabling continuous data transfer.
Idle state
(mark state)
1
LSB
MSB
1
Serial
data
0 D0 D1 D2 D3 D4 D5 D6 D7 0/1 1 1
Start
bit
Transmit/receive data
Parity
bit Stop bit
1 bit
7 or 8 bits
1 bit 1 or 2 bits
or
none
One unit of transfer data (character or frame)
Figure 10.2 Data Format in Asynchronous Communication (Example with 8-Bit Data,
Parity, Two Stop Bits)
10.4.1 Data Transfer Format
Table 10.8 shows the data transfer formats that can be used in asynchronous mode. Any of 12
transfer formats can be selected according to the SMR setting. For details on the multiprocessor
bit, refer to section 10.5, Multiprocessor Communication Function.
Rev.2.00 Sep. 27, 2007 Page 296 of 448
REJ09B0394-0200