Fujitsu FR81S User Manual
CHAPTER 40: MULTI-FUNCTION SERIAL INTERFACE
4. Registers
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : MULTI-FUNCTION SERIAL INTERFACE
FUJITSU SEMICONDUCTOR CONFIDENTIAL
123
Bit name
Function
bit1 TDRE:
Transmission data empty
flag bit
"0" Read: Transmit data register (TDR) contains data.
"1" Read: Transmit data register (TDR) is empty.
⋅
The flag indicates the state of the transmit data register (TDR).
⋅
When the TDRE bit and the SMR:TIE bit are set to "1", a transmission
interrupt request will be output.
⋅
When a transmit data is written to TDR, this flag turns to "0", which
indicates that a valid data exists in the TDR. Once a transmission starts
after data being loaded to the transmit shift register, the bit will be set to
"1", which indicates that the TDR does not contain any valid data.
⋅
Writing "1" to TSET bit on the serial status register (SSR) results in a
setting. Use this flag for setting "1" to the TDRE bit when detecting an
arbitration lost or a bus error.
bit0 TBI:
Transmission bus idle flag
bit (Only the DMA mode
enabled is effective.)
"0" is read: Transmitting
"1" is read: Not transmitting
This bit is a bit that shows that I
2
C doesn't do the transmission operation
when the DMA mode is enabled (DMA=1). When SCL is made "L", and
the TBI bit becomes "0" when the TBI bit becomes "1" in the 2nd or
subsequent byte in DMA mode permission (DMA=1), the state of "L" of
SCL is released.
Set condition of TBI bit:
<8th bit>
(1) In the 2nd or subsequent byte, the SSR:TDRE bit is "1" while WSEL is
"1" and the master operating
(2) In the 2nd or subsequent byte, the SSR:TDRE bit is "1" while WSEL is
"1" and the slave transmitting
<9th bit>
(1) The SSR:TDRE bit is "1" while reservation address is not detected in
the first byte and the master is operating
(2) In the 2nd or subsequent byte, the SSR:TDRE bit is "1" while WSEL is
"0" and the master operating
(3) In the 2nd or subsequent byte, the SSR:TDRE bit is "1" while WSEL is
"0" and the slave transmitting
<Other>
When transmission buffer empty flag set bit (TSET) is set to "1"
Reset condition of TBI bit:
When writing transmission data in transmission data register (TDR)
When this bit is "1" and transmission bus idle interrupt is enabled
(SCR:TBIE=1), this bit outputs the transmission interrupt request.
When the DMA mode is disabled (DMA="0"), this bit becomes irregular.
MB91520 Series
MN705-00010-1v0-E
1436