R5F72115D160FPV datasheet(725/1228 Pages) RENESAS

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Section 15 Serial Communication Interface with FIFO (SCIF)

Rev. 2.00 May. 08, 2008 Page 701 of 1200

REJ09B0344-0200

15.4.2

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.

The transmitting and receiving sections of the SCIF are independent, so full duplex

communication is possible. The transmitter and receiver are 16-byte FIFO buffered, so data can be

written and read while transmitting and receiving are in progress, enabling continuous transmitting

and receiving.

Figure 15.2 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 character consists of a start bit (low), data (LSB

first), parity bit (high or low), and stop bit (high), in that order.

When receiving in asynchronous mode, the SCIF synchronizes at the falling edge of the start bit.

The SCIF samples each data bit on the eighth pulse of a clock with a frequency 16 times* the bit

rate. Receive data is latched at the center of each bit.

0/1

(LSB)

(MSB)

Start

bit

Idle state (mark state)

Stop bit

Transmit/receive data

Serial

data

Parity

bit

1 bit

1 or 2 bits

7 or 8 bits

1 bit

none

One unit of transfer data (character or frame)

Figure 15.2 Example of Data Format in Asynchronous Communication

(8-Bit Data with Parity and Two Stop Bits)

Note: * This is an example when ABCS = 0 in SCSEMR. When ABCS = 1, a frequency of 8

times the bit rate becomes the basic clock, and receive data is sampled at the fourth

rising edge of the basic clock.

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