
CHAPTER 15 ASYNCHRONOUS SERIAL INTERFACE (UART)
User
’
s Manual U15862EJ3V0UD
449
(3) Asynchronous serial interface transmission status register n (ASIFn)
The ASIFn register, which consists of 2 status flag bits, indicates the status during transmission.
By writing the next data to the TXBn register after data is transferred from the TXBn register to the
transmission shift register, transmit operations can be performed continuously without suspension even
during an interrupt interval. When transmission is performed continuously, data should be written after
referencing the TXBFn bit of the ASIFn register to prevent writing to the TXBn register by mistake.
This register is read-only in 8-bit units.
7
0
ASIFn
6
0
5
0
4
0
3
0
2
0
<1>
TXBFn
<0>
TXSFn
After reset: 00H R Address: FFFFFA05H, FFFFFA15H, FFFFFA25H
TXBFn
0
Transmission buffer data flag
Data to be transferred next to TXBn register does not exist (When the ASIMn register
’
s UARTEn or TXEn
bits is 0, or when data has been transferred to the transmission shift register)
1
Data to be transferred next exists in TXBn register (Data exists in TXBn register when the TXBn register
has been written to)
When transmission is performed continuously, data should be written to the TXBn register after confirming that
this flag is 0. If writing to TXBn register is performed when this flag is 1, transmit data cannot be guaranteed.
TXSFn
Transmission shift register data flag (indicates the transmission status of UARTn)
0
Initial status or a waiting transmission (When the ASIMn register
’
s UARTEn or TXEn bits is set to 0, or
when following transfer completion, the next data transfer from the TXBn register is not performed)
1
Transmission in progress (When data has been transferred from the TXBn register)
When the transmission unit is initialized, initialization should be executed after confirming that this flag is 0
following the occurrence of a transmission completion interrupt. If initialization is performed when this flag is 1,
transmit data cannot be guaranteed.
Remark
n = 0, 1 (V850ES/KF1, V850ES/KG1)
n = 0 to 2 (V850ES/KJ1)