NEC uPD78056Y User Manual
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463
CHAPTER 19 SERIAL INTERFACE CHANNEL 2
(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 19-8. Asynchronous Serial Interface Transmission Completion
Interrupt Request Generation Timing
(a) Stop bit length: 1
(b) Stop bit length: 2
Caution Do not rewrite the asynchronous serial interface mode register (ASIM) 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).
Whether transmission is in progress or not can be determined by software using a
transmission completion interrupt (INTST) or the interrupt request flag (STIF) set by
the INTST.
D1
D2
D6
D7
Parity
D0
TxD (Output)
INTST
STOP
START
D1
D2
D6
D7
Parity
D0
TxD (Output)
INTST
STOP
START