Operation In Asynchronous Mode; Serial Data Transfer Format - Renesas RX100 Series User Manual

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Operation in Asynchronous Mode

Figure 23.4 shows the general format for asynchronous serial communications.

One frame consists of a start bit (low level), transmit/receive data, a parity bit, and stop bits (high level).

In asynchronous serial communications, the communications line is usually held in the mark state (high level).

The SCI monitors the communications line. When the SCI detects a low, it regards that as a start bit and starts serial

communication.

Inside the SCI, the transmitter and receiver are independent units, enabling full-duplex communications. 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 transmission and reception.

Data Format in Asynchronous Serial Communications

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

Table 23.27 lists the serial data transfer formats that can be used in asynchronous mode.

Any of 18 transfer formats can be selected according to the SMR and SCMR setting. For details of multi-processor

function, refer to section 23.4, Multi-Processor Communications Function .

R01UH0822EJ0100 Rev.1.00

Jul 31, 2019

Transmit/receive data

One unit of transfer data (character or frame)

23. Serial Communications Interface (SCIg, SCIh)

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(mark state)