UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 452

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

16.2.5 Transmission
asynchronous serial interface mode register (ASIM) is set (1). A transmit operation is started by writing transmit data to
the transmit shift register (TXS) when transmission is enabled. The start bit, parity bit and stop bit(s) are added automatically.
is generated when the TXS is empty.
412
The PD784026’s asynchronous serial interface is set to the transmission enabled state when the TXE bit of the
When a transmit operation is started, the data in the TXS is shifted out, and a transmission completion interrupt (INTST)
If no more data is written to the TXS, the transmit operation is discontinued.
If the TXE bit is cleared (0) during a transmit operation, the transmit operation is discontinued immediately.
Cautions 1. After RESET input the transmit shift register (TXS) is emptied but a transmission completion
(a) Stop bit length: 1
(b) Stop bit length: 2
TxD (Output)
TxD (Output)
Figure 16-6 Asynchronous Serial Interface Transmission Completion Interrupt Timing
2. An asynchronous serial interface mode register (ASIM) rewrite should not be performed during
INTST
INTST
interrupt is not generated. A transmit operation can be started by writing transmit data to the TXS.
a transmit operation. If an ASIM rewrite is performed during a transmit operation, subsequent
transmit operations may not be possible (normal operation is restored by RESET input).
Software can determine whether transmission is in progress by using a transmission completion
interrupt (INTST) or the interrupt request flag (STIF) set by INTST.
CHAPTER 16 ASYNCHRONOUS SERIAL INTERFACE/3-WIRE SERIAL I/O
START
START
D0
D0
D1
D1
D2
D2
D6
D6
D7
D7
Parity
Parity
STOP
STOP