Asynchronous Serial Interface Transmission Completion Interrupt Request Timing - NEC PD78081(A) User Manual

(c) Transmission
A transmit operation is started by writing transmit data to the transmit shift register (TXS). The start bit,
parity bit and stop bit(s) are added automatically.
When the transmit operation starts, the data in the transmit shift register (TXS) is shifted out, and when
the transmit shift register (TXS) is empty, a transmission completion interrupt request (INTST) is
generated.
Figure 11-8. Asynchronous Serial Interface Transmission Completion Interrupt Request Timing
TxD (Output)
INTST
TxD (Output)
INTST
Caution Rewriting of the asynchronous serial interface mode register (ASIM) should not be
performed during a transmit operation. If rewriting of the ASIM register is performed
during transmission, subsequent transmit operations may not be possible (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 request (INTST) or the interrupt request flag (STIF)
set by the INTST.
CHAPTER 11 SERIAL INTERFACE CHANNEL 2
(a) Stop bit length: 1
D0 D1 D2
START
(b) Stop bit length: 2
D0 D1 D2
START
STOP
D6 D7 Parity
D6 D7 Parity
STOP
159