CHAPTER 10 SERIAL INTERFACE FUNCTION
User’s Manual U15195EJ5V0UD
454
(2) Transmission operation
The transmission operation is started by writing data to 2-frame continuous transmission shift register 1
(TXS1)/transmit shift register L1 (TXSL1).
Following data write, the start bit is transmitted from the next shift timing.
Since the UART1 does not have a CTS (transmission enable signal) input pin, use a port when the other
party confirms the reception enabled status.
(a) Transmission operation start
The transmission operation is started by writing transmit data to 2-frame continuous transmission shift
register 1 (TXS1)/transmit shift register L1 (TXSL1). Then data is output in sequence from LSB to the
TXD1 pin (transmission in sequence from the start bit). A start bit, parity bit, and stop bit(s) are
automatically added.
(b) Transmission interrupt request
When the transmit shift register becomes empty upon completion of the transmission of 1 or 2 frames of
data, a transmission completion interrupt request (INTST1) is generated. The INTST1 interrupt
generation timing differs depending on the specification of the stop bit length. The INTST1 interrupt is
generated at the same time that the last stop bit is output.
The transmission operation remains stopped until the data to be transmitted next has been written to the
TXS1/TXSL1 registers.
Figure 10-18 shows the INTST1 interrupt generation timing.
Cautions 1. Normally, the transmission completion interrupt (INTST1) is generated when the
transmit shift register becomes empty. However, if the transmit shift register has
become empty due to input of RESET, no transmission completion interrupt (INTST1) is
generated.
2. No data can be written to the TXS1 or TXSL1 registers during a transmission operation
until INTST1 is generated. Even if data is written, this does not affect the transmission
operation.
Содержание PD703114
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