NEC 78K0S/KA1+ User Manual page 186

(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 is read-only by an 8-bit memory manipulation instruction.
Reset signal generation clears this register to 00H if bit 7 (POWER6) and bit 6 (TXE6) of ASIM6 = 0.
Figure 11-7. Format of Asynchronous Serial Interface Transmission Status Register 6 (ASIF6)
Address: FF95H After reset: 00H R
Symbol 7
ASIF6 0
TXBF6
0
1
TXSF6
0
1
Cautions 1. To transmit data continuously, write the first transmit data (first byte) to the TXB6 register.
Be sure to check that the TXBF6 flag is "0". If so, write the next transmit data (second byte)
to the TXB6 register. If data is written to the TXB6 register while the TXBF6 flag is "1", the
transmit data cannot be guaranteed.
2. To initialize the transmission unit upon completion of continuous transmission, be sure to
check that the TXSF6 flag is "0" after generation of the transmission completion interrupt,
and then execute initialization. If initialization is executed while the TXSF6 flag is "1", the
transmit data cannot be guaranteed.
186
CHAPTER 11 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)
User's Manual U16898EJ3V0UD
4 3 2
0 0 0
Transmit buffer data flag
Transmit shift register data flag
1 0
TXBF6 TXSF6