SH7713 datasheet(601/904 Pages) RENESAS

601 / 904 page

Section 16 Serial Communication Interface with FIFO (SCIF)

Rev.1.50 Aug. 30, 2006 Page 561 of 860

REJ09B0288-0150

16.4.2

Serial Operation in Asynchronous Mode

In asynchronous mode, each transmitted or received character begins with a start bit and ends with

a stop bit. Serial communication is synchronized one character at a time. Figure 16.2 shows the

general format of asynchronous serial communication.

In asynchronous serial communication, the communication line is normally held in the mark

(high) state. The SCIF monitors the line and starts serial communication when the line goes to the

space (low) state, indicating a start bit. One serial communication character consists of a start bit

(low), data (LSB first), parity bit (high/low), and stop bit (high), in this order. In asynchronous

mode, the SCIF synchronizes at the falling edge of the start bit during reception. The SCIF

samples each data bit on the eighth pulse of a clock with a frequency 16 times the bit rate.

Therefore, communication data is latched at the center of each bit.

0/1

Start

bit

Parity

bit

Stop bit

1 bit

7 bits or 8 bits

1 bit or

no bit

1 bit or

2 bits

One unit of communication data (character or frame)

Idle state (mark state)

Transmit/Receive data

Serial

data

Figure 16.2 Data Format in Asynchronous Communication

(Example of 8-Bit Data with Parity and 2 Stop Bits)

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