CHAPTER 10 SERIAL INTERFACE FUNCTION
User’s Manual U12688EJ4V0UM00
296
(b) Starting a transmit operation
In the transmit enabled state, if data is written to the transmit shift register (TXSn or TXSnL), the transmit
operation starts. Transmit data is transmitted from the start bit to the LSB header. A start bit,
parity/expansion bit and stop bit are added automatically.
In the transmit disabled state, data is not written to the transmit shift register. Even if writing is done, the
values are disregarded.
(c) Transmission interrupt request
If the transmit shift register (TXSn or TXSnL) becomes empty, a transmission complete interrupt request
(INTSTn) is generated.
If the next transmit data is not written to the TXSn or TXSnL register, the transmit operation is interrupted.
After 1 transmission is ended, the transmission rate drops if the next transmit data is not written to the
TXSn or TSXnL register immediately.
Cautions
1. Normally, when the transmit shift register (TXSn or TXSnL) has become empty, a
transmission complete interrupt (INTSTn) is generated. However, when RESET is
input, if the transmit shift register (TXSn or TXSnL) has become empty, a
transmission complete interrupt (INTSTn) is not generated.
2. During a transmit operation before INTSTn generation, even if data is written to the
TXSn or TXSnL register, the written data is invalid.
Figure 10-3. Asynchronous Serial Interface Transmission Completion Interrupt Timing
Start
Stop
D0
D1
D2
D6
D7
Parity/
expansion
TXDn (output)
INTSTn interrupt
Start
D0
D1
D2
D6
D7
TXDn (output)
INTSTn interrupt
Stop
(a) Stop bit length: 1
(b) Stop bit length: 2
Parity/
expansion
Remark
n = 0, 1
Summary of Contents for V850E/MS1 UPD703100
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