NEC 78K0/KD1 Series User Manual page 278

(3) Asynchronous serial interface transmission status register 6 (ASIF6)
This register indicates the status of transmission by serial interface UART6. It includes two status flag bits
(TXBF6 and TXSF6).
Transmission can be continued without disruption even during an interrupt period, by writing the next data to the
TXB6 register after data has been transferred from the TXB6 register to the TXS6 register.
This register can be set by an 8-bit memory manipulation instruction, and is read-only.
RESET input clears this register to 00H if bit 7 (POWER6) and bit 6 (TXE6) of ASIM6 = 0.
Figure 14-7. Format of Asynchronous Serial Interface Transmission Status Register 6 (ASIF6)
Address: FF55H After reset: 00H R
Symbol 7
ASIF6 0
TXBF6
0
1
TXSF6
0
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 complete. Data of 2 bytes can be written. When
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). If clearing is
executed while the TXSF6 flag is 1, the transmit data cannot be guaranteed.
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CHAPTER 14 SERIAL INTERFACE UART6
6 5
0 0
If POWER6 = 0 or TXE6 = 0, or if data is transferred to transmit shift register 6 (TXS6)
If data is written to transmit buffer register 6 (TXB6) (if data exists in TXB6)
If POWER6 = 0 or TXE6 = 0, or if the next data is not transferred from transmit buffer register 6
(TXB6) after completion of transfer
If data is transferred from transmit buffer register 6 (TXB6) (if data transmission is in progress)
doing so, observe Caution 1 above.
Preliminary User's Manual U16315EJ1V0UD
4 3 2
0 0 0
Transmit buffer data flag
Transmit shift register data flag
1 0
TXBF6 TXSF6