Fujitsu FR81S User Manual
CHAPTER 40: MULTI-FUNCTION SERIAL INTERFACE
4. Registers
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : MULTI-FUNCTION SERIAL INTERFACE
FUJITSU SEMICONDUCTOR CONFIDENTIAL
121
4.5.2.
Serial Status Register: SSR
Serial status register (SSR) checks for the transmission/reception states.
SSRn(3 to 8, 10, 11) : Address Base addr + 02
H
(Access: Byte, Half-word,
Word)
7
6
5
4
3
2
1
0
bit
REC
TSET
DMA
TBIE
ORE
RDRF
TDRE
TBI
0
0
0
0
0
0
1
1
Initial value
R0,W
R0,W
R/W
R/W
R,WX
R,WX
R,WX
R,WX
Attribute
Bit name
Function
bit7 REC:
Reception error flag clear
bit
This bit clears the ORE bit of serial status register (SSR)
⋅
Writing "1" clears the ORE bit.
⋅
Writing "0" does not affect anything.
A read always results in "0".
bit6 TSET:
Transmit buffer empty flag
set bit
This bit sets the TDRE bit in serial status register (SSR)
⋅
Writing "1" sets the TDRE bit.
⋅
Writing "0" does not affect anything.
A read always results in "0".
Note:
Write "1" in this bit when the IBCR:INT bit is "1".
bit5 DMA:
DMA mode enable bit
This bit enables/disables the DMA mode.
⋅
When this bit is set in "1", it becomes an interrupt condition
corresponding to the DMA Transfer.
⋅
When usually transfer it, it becomes an interrupt condition when this bit
is set in "0".
See Table 8-1 "I
2
C Interface Interrupt Control Bits and Interrupt Factors"
for details.
"0": DMA mode is disabled
"1": DMA mode is enabled
Note:
⋅
When ISMK:EN=0 only, this bit can be change.
bit6 TBIE:
Transmission bus idle
interrupt enabled bit (Only
the DMA mode enabled is
effective.)
This bit is used to set TDRE bit of serial status register (SSR).
⋅
This bit enables/disables transmission bus idle interrupt request output to
the CPU.
⋅
The transmission bus idle interrupt request will be output when DMA
mode is enabled (DMA="1") and both TBIE bit and TBI bit are "1".
⋅
When DMA mode is disabled (DMA="0"), this bit becomes "0" and any
writing operation will be ignored and "0" will be retained.
When "0": Transmission bus idle interrupt request is disabled
When "1": Transmission bus idle interrupt request is enabled
bit3 ORE:
Overrun error flag bit
"0" Read: No overrun error
"1" Read: There is an overrun error
⋅
If an overrun error occurs while a reception is in progress, this bit will be
set to "1". To clear this bit, write "1" to the REC bit of the serial status
register (SSR).
⋅
When the ORE bit and SMR:RIE bit are set to "1", a reception interrupt
request will be output.
⋅
If this flag is set, the receive data register (RDR) will be disabled.
⋅
When you are using the reception FIFO, if this flag is set, the received
data will not be stored in the reception FIFO.
MB91520 Series
MN705-00010-1v0-E
1434