CHAPTER 12 SERIAL INTERFACE FUNCTION
Preliminary User’s Manual U15905EJ1V0UD
313
(3) Continuous transmission operation
UARTn can write the next transmit data to the TXBn register at the timing that the transmit shift register starts
the shift operation. This enables an efficient transmission rate to be realized by continuously transmitting data
even during the INTSTn interrupt servicing after the transmission of one data frame. In addition, reading the
TXSFn bit of the ASIFn register after the occurrence of a transmission completion interrupt enables the TXBn
register to be efficiently written twice (2 bytes) without waiting for the transmission of 1 data frame.
When continuous transmission is performed, data should be written after referencing the ASIFn register to
confirm the transmission status and whether or not data can be written to the TXBn register.
TXBFn
Whether or Not Writing to TXBn Register Is Enabled
0
Writing is enabled
1
Writing is not enabled
Caution
When transmission is performed continuously, write the first transmit data (first byte) to the
TXBn register and confirm that the TXBFn bit is 0, and then write the next transmit data
(second byte) to TXBn register. If writing to the TXBn register is performed when the TXBFn
bit is 1, transmit data cannot be guaranteed.
While transmission is being performed continuously, whether writing to the TXBn register later is enabled can
be judged by confirming the TXSFn bit after the occurrence of a transmission completion interrupt.
TXSFn
Transmission Status
0
Transmission is completed. However, the cautions concerning the TXBFn bit
must be observed. Writing transmit data can be performed twice (2 bytes).
1
Under transmission. Transmit data can be written once (1 byte).
Cautions 1.
When initializing the transmission unit when continuous transmission is completed,
confirm that the TXBFn bit is 0 after the occurrence of the transmission completion
interrupt, and then execute initialization. If initialization is performed when the TXBFn bit
is 1, transmit data cannot be guaranteed.
2. While transmission is being performed continuously, an overrun error may occur if the
next transmission is completed before the INTSTn interrupt servicing following the
transmission of 1 data frame is executed. An overrun error can be detected by
embedding a program that can count the number of transmit data and referencing the
TXSFn bit.
Содержание V850ES/SA2 UPD703201
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