Operation In Asynchronous Mode - Renesas H8S/2100 Series Hardware Manual

6-bit single-chip microcomputer

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Operation in Asynchronous Mode

Figure 14.2 shows the general format for asynchronous serial communication. One frame consists

of a start bit (low level), followed by transmit/receive 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 transmission 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 and reception.

Figure 14.2 Data Format in Asynchronous Communication

Transmit/receive data

One unit of transfer data (character or frame)

(Example with 8-Bit Data, Parity, Two Stop Bits)

Section 14 Serial Communication Interface (SCI)

Rev. 1.00 May 09, 2008 Page 383 of 954

(mark state)

REJ09B0462-0100