7733 datasheet(252/940 Pages) RENESAS

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SERIAL I/O

7733 Group User’s Manual

8–49

8.4 Clock asynchronous serial I/O (UART) mode

8.4.3 Method of transmission

Figure 8.4.3 shows an initial setting example for related registers when transmitting.

The difference derived by selection of transfer data length (7 bits, 8 bits, or 9 bits) is only that data is

transmitted in different lengths. When a 7/8-bit data length is selected, set the transmit data in the low-

order byte of the UARTi transmission buffer register; when a 9-bit data length is selected, set the transmit

data in the low-order byte and bit 0 of the high-order byte.

Transmission is started when the following conditions ( to ) are satisfied:

Transmit enable state (transmit enable bit = “1”)

Transmit data is present in the UARTi transmission buffer register (transmission buffer empty flag = “0”)

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The CTSi pin’s input is at “L” level (when the CTS function is selected)

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Note: When the CTS function is not selected or in UART2, this condition is ignored.

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By connecting the RTSi pin (receiver side) and CTSi pin (transmitter side), the timing of transmission and

that of reception can be matched (UART0, UART1). For details, refer to section “8.4.6 Receive operation.”

When using interrupts, settings for enabling interrupts are required. For details, refer to chapter “4. Interrupts.”

Figure 8.4.4 shows how to write data after transmission is started and Figure 8.4.5 shows how to detect

the transmit completion.

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