Operation In Asynchronous Mode - Renesas RZ/A Series User Manual

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RZ/A1L Group, RZ/A1LU Group, RZ/A1LC Group

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 in this module are independent, so full duplex communication is possible. The

transmitter and receiver are 16-stage FIFO buffered, so data can be written and read while transmitting and receiving are

in progress, enabling continuous transmitting and receiving.

Figure 14.2 shows the general format of asynchronous serial communication.

In asynchronous serial communication, the communication line is normally held in the mark (high) state. This module

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, this module synchronizes at the falling edge of the start bit. This module samples

each data bit on the eighth or fourth pulse of a clock with a frequency 16 or 8 times the bit rate; receive data is latched at

the center of each bit.

Example of Data Format in Asynchronous Communication

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

R01UH0437EJ0600 Rev.6.00

Jan 29, 2021

Transmit/receive data

One unit of transfer data (character or frame)

14. Serial Communication Interface with FIFO

Idle state (mark state)

Rz/a1 series Rz/a1lu series Rz/a1lc series