CHAPTER 11 SERIAL INTERFACE UART0 (
µ
PD78F0102H AND 78F0103H ONLY)
Preliminary User’s Manual U16846EJ1V0UD
215
(c) Transmission
The T
X
D0 pin outputs a high level when bit 7 (POWER0) of asynchronous serial interface operation 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 11-8 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 11-8. 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