Starting Uart Transmission; Successive Uart Transmission - Mitsubishi Electric M32R Series User Manual

Mitsubishi 32-bit risc single-chip microcomputers

Table of Contents

12.6.4 Starting UART Transmission

When all of the following transmit conditions are met after you finished initialization, the serial I/O

starts transmit operation.

• The SIO Transmit Control Register's TEN (transmit enable) bit is set to 1. (Note)

• Transmit data is written to the SIO Transmit Buffer Register (transmit buffer empty bit = 0).

Note : While the transmit enable bit is cleared to 0, writes to the transmit buffer are ignored.

Always be sure to set the transmit enable bit to 1 before you write to the transmit buffer

When transmission starts, the serial I/O transmits data following the procedure 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)

• Start sending data synchronously with the shift clock beginning with the LSB.

Note : A transmit buffer empty interrupt request and/or a DMA transfer request can be generated

when the transmit buffer is emptied.

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

can be written to the transmit buffer register even when transmission of the preceding data is not

completed. When the next data is written to the transmit buffer before completion of the preceding

data transmission, the preceding and the next data are successively transmitted.

To see if data has been transferred from the transmit buffer register to the transmit shift register,

check the SIO Transmit Control Register's transmit buffer empty flag.

12.6 Transmit Operation in UART Mode