Asynchronous Serial Interface Transmission Completion Interrupt Timing - NEC PD789488 User Manual

(c) Transmission
A transmit operation is started by writing transmit data to transmit shift register 20 (TXS20). The start bit,
parity bit, and stop bit(s) are added automatically.
When the transmit operation starts, the data in TXS20 is shifted out, and when TXS20 is empty, a
transmission completion interrupt (INTST20) is generated.
Figure 11-8. Asynchronous Serial Interface Transmission Completion Interrupt Timing
TxD20 (output)
INTST20
TxD20 (output)
INTST20
Caution Do not rewrite asynchronous serial interface mode register 20 (ASIM20) during a
transmit operation. If the ASIM20 register is rewritten during transmission, subsequent
transmission may not be able to be performed (the normal state is restored by RESET
input).
It is possible to determine whether transmission is in progress by software by using a
transmission completion interrupt (INTST20) or the interrupt request flag (STIF20) set
by INTST20.
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CHAPTER 11 SERIAL INTERFACE 20
(a) Stop bit length: 1
D0 D1 D2
START
(b) Stop bit length: 2
D0 D1 D2
START
User's Manual U15331EJ4V1UD
STOP
D6 D7 Parity
D6 D7 Parity
STOP