SH7708 datasheet(402/633 Pages) RENESAS

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13.3.4

Synchronous Operation

In synchronous mode, the SCI transmits and receives data in synchronization with clock pulses.

This mode is suitable for high-speed serial communication.

The SCI transmitter and receiver are independent, so full-duplex communication is possible while

sharing the same clock. The transmitter and receiver are also double-buffered, so continuous

transmitting or receiving is possible by reading or writing data while transmitting or receiving is in

progress.

Figure 13.14 shows the general format in synchronous serial communication.

Bit 0

care

Don’t

care

Don’t

Bit 1

Bit 2

Bit 3

Bit 4

Bit 5

Bit 6

Bit 7

LSB

MSB

Serial clock

Serial data

One unit of communication data (character or frame)

Note:

* High except in continuous transmitting or receiving

Figure 13.14 Data Format in Synchronous Communication

In synchronous serial communication, each data bit is output on the communication line from one

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

clock. In each character, the serial data bits are transmitted in order from the LSB (first) to the

MSB (last). After output of the MSB, the communication line remains in the state of the MSB. In

synchronous mode, the SCI transmits or receives data by synchronizing with the falling edge of

the serial clock.

Communication Format: The data length is fixed at eight bits. No parity bit or multiprocessor bit

can be added.

Clock: An internal clock generated by the on-chip baud rate generator or an external clock input

from the SCK pin can be selected as the SCI transmit/receive clock. The clock source is selected

by the C/

A bit in the serial mode register (SCSMR) and bits CKE1 and CKE0 in the serial control

When the SCI operates on an internal clock, it outputs the clock signal at the SCK pin. Eight clock

pulses are output per transmitted or received character. When the SCI is not transmitting or

receiving, the clock signal remains in the high state. When only receiving, the SCI receives in 2-

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