32186 datasheet(580/1032 Pages) RENESAS

580 / 1032 page

SERIAL INTERFACE

12-32

32185/32186 Group Hardware Manual

Rev.1.10 REJ09B0235-0110 May 15, 07

12.3.3 Starting CSIO Transmission

The serial interface starts a transmit operation when all of the following conditions are met after being

initialized.

(1) Transmit conditions when CSIO mode internal clock is selected

• The SIO Transmit Control Register transmit enable bit is set to "1."

• Transmit data (8-16 bits) is written to the lower byte of the SIO Transmit Buffer Register (transmit buffer

empty bit = "0") (Note 1) (Note 2)

(2) Transmit conditions when CSIO mode external clock is selected

• The SIO Transmit Control Register transmit enable bit is set to "1."

• Transmit data is written to the lower byte of the SIO Transmit Buffer Register (transmit buffer empty bit =

"0") (Note 1)

• A falling edge of transmit clock on the SCLKI pin is detected.

When transmission starts, the serial interface sends data following the procedure described below.

• Transfer the content of the SIO Transmit Buffer Register to the SIO Transmit Shift Register.

• Set the transmit buffer empty bit to "1" (Note 3).

• Start sending data synchronously with the shift clock.

Note 1: While the transmit enable bit is cleared to "0," writes to the Transmit Buffer Register are

ignored. Always set the transmit enable bit to "1" before writing to the Transmit Buffer

the SIO Transmit Buffer Register.

Note 2: When the internal clock is selected, a write to the lower byte of the Transmit Buffer

Note 3: A transmit interrupt request can be generated for reasons that the transmit buffer is empty or

transmission has finished. Also, a DMA transfer request can be generated when the transmit

buffer is empty. No DMA transfer requests can be generated for reasons that transmission has

finished.

12.3.4 Successive CSIO Transmission

Once data has been transferred from the transmit buffer register to the transmit shift register, the next data

can be written to the transmit buffer register even when the serial interface has not finished sending the

previous data. If the next data is written to the transmit buffer register before transmission has finished, the

previous and the next data are transmitted successively.

Check the SIO Transmit Control Register’s Status Register’s transmit buffer empty flag to see if data has

been transferred from the transmit buffer register to the transmit shift register.

12.3 Transmit Operation in CSIO Mode

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