Datasheet

Section 17 Serial Communication Interface with FIFO (SCIF)

Rev. 2.00 Sep. 28, 2009 Page 515 of 994

REJ09B0452-0200

17.4.2 Operation in Asynchronous Communication

Figure 17.2 illustrates the typical format for asynchronous serial communication. One frame

consists of a start bit (low level), followed by transmit/receive data (LSB-first: from the least

significant bit), a parity bit, and a stop bit (high level). In asynchronous serial communication, the

transmission line is usually held high in the mark state (high level). The SCIF monitors the

transmission line, and when it detects the space state (low level), recognizes a start bit and starts

serial communication. Inside the SCIF, the transmitter and receiver are independent units,

enabling full-duplex communication. Both of the transmitter and receiver also have a 16-stage

FIFO buffered structure so that data can be read or written during transmission or reception,

enabling continuous data transmission and reception.

Serial data

D0 D1 D2 D3 D4 D5 D6 D7 0/1

Idle state (mark state)

Transmit/receive data

Stop bit

1, 1.5,

2 bits

1 bit

none

5, 6, 7, or 8 bits

Start

bit

Parity

bit

One unit of transfer data (character or frame)

Figure 17.2 Data Format in Serial Transmission/Reception

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