H8S2245 datasheet(495/818 Pages) RENESAS

495 / 818 page

Section 12 Serial Communication Interface (SCI)

Rev.3.00 Mar. 26, 2007 Page 453 of 772

REJ09B0355-0300

12.3.4

Operation in Clocked Synchronous Mode

In clocked synchronous mode, data is transmitted or received in synchronization with clock

pulses, making it suitable for high-speed serial communication.

Inside the SCI, the transmitter and receiver are independent units, enabling full-duplex

communication by use of a common clock. 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.

Figure 12.14 shows the general format for clocked synchronous serial communication.

Don't care

One unit of transfer data (character or frame)

Bit 0

Serial

data

Serial

clock

Bit 1

Bit 3

Bit 4

Bit 5

LSB

MSB

Bit 2

Bit 6

Bit 7

Note: * High except in continuous transfer

Figure 12.14 Data Format in Synchronous Communication

In clocked synchronous serial communication, data on the transmission line is output from one

falling edge of the serial clock to the next. Data confirmation is guaranteed at the rising edge of

the serial clock.

In clocked serial communication, one character consists of data output starting with the LSB and

ending with the MSB. After the MSB is output, the transmission line holds the MSB state.

In clocked synchronous mode, the SCI receives data in synchronization with the rising edge of the

serial clock.

Data Transfer Format

A fixed 8-bit data format is used.

No parity or multiprocessor bits are added.

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