CHAPTER 13 SERIAL INTERFACE UART0
Preliminary User’s Manual U16315EJ1V0UD
259
(c) Transmission
The T
X
D0 pin outputs a high level when bit 7 (POWER0) of asynchronous serial interface mode register 0
(ASIM0) is set to 1. If bit 6 (TXE0) of ASIM0 is then set to 1, transmission is enabled. Transmission can be
started by writing transmit data to transmit shift register 0 (TXS0). The start bit, parity bit, and stop bit are
automatically appended to the data.
When transmission is started, the start bit is output from the T
X
D0 pin, followed by the rest of the data in
order starting from the LSB. When transmission is completed, the parity and stop bits set by ASIM0 are
appended and a transmission completion interrupt request (INTST0) is generated.
Transmission is stopped until the data to be transmitted next is written to TXS0.
Figure 13-7 shows the timing of the transmission completion interrupt request (INTST0). This interrupt
occurs as soon as the last stop bit has been output.
Caution
After transmit data is written to TXS0, do not write the next transmit data before the
transmission completion interrupt signal (INTST0) is generated.
Figure 13-7. Normal Transmission Completion Interrupt Request Timing
1. Stop bit length: 1
INTST0
D0
START
D1
D2
D6
D7
STOP
T
X
D0 (output)
Parity
2. Stop bit length: 2
T
X
D0 (output)
INTST0
D0
START
D1
D2
D6
D7
Parity
STOP