NEC 78K0/KD1 Series User Manual page 294

(d) Continuous transmission
When transmit shift register 6 (TXS6) has started the shift operation, the next transmit data can be written to
transmit buffer register 6 (TXB6). As a result, data can be transmitted without intermission even while an
interrupt that has occurred after transmission of one data frame is being serviced, thus realizing an efficient
communication rate. To transmit data continuously, however, transmission processing must be executed
while referencing bits 1 (TXBF6) and 0 (TXSF6) of asynchronous serial interface transmission status register
6 (ASIF6).
Caution When the device is incorporated in LIN, the continuous transmission function cannot be
used. Make sure that asynchronous serial interface transmission status register 6 (ASIF6)
is 00H before writing transmit data to transmit buffer register 6 (TXB6).
Table 14-2. Write Processing and Writing to TXB6 During Execution of Continuous Transmission
TXBF6 TXSF6
0
0
1
1
Cautions 1. To continuously transmit data, write the data of the first byte to TXB6, check that the
value of the TXBF6 flag is 0, and then write the data of the second byte to TXB6. The
operation is not guaranteed if data is written to TXB6 while the TXBF6 flag is 1.
2. While continuous transmission is being executed, check the value of the TXSF6 flag
after the transmission completion interrupt to determine the subsequent write
processing to TXB6.
• • • • If TXSF6 is 1: Continuous transmission is in progress. Data of 1 byte can be written.
• • • • If TXSF6 is 0: Continuous transmission is completed. Data of 2 bytes can be written.
3. While continuous transmission is in progress, check that TXSF6 is 0 after the
transmission completion interrupt, and then execute clearing (POWER6 = 0 or TXE6 =
0).
guaranteed.
294
CHAPTER 14 SERIAL INTERFACE UART6
Write Processing During Execution of
Continuous Transmission
0 Enables writing 2 bytes or
transmission completion processing
1 Enables writing 1 byte
0 Enables writing 2 bytes or
transmission completion processing
1 Enables writing 1 byte
To do so, observe Caution 1 above.
If clearing is executed while the TXSF6 flag is 1, the transmit data cannot be
Preliminary User's Manual U16315EJ1V0UD
Writing to TXB6 During Execution of
Continuous Transmission
Enables writing
Enables writing
Disables writing
Disables writing