Fujitsu FR81S User Manual
CHAPTER 40: MULTI-FUNCTION SERIAL INTERFACE
4. Registers
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : MULTI-FUNCTION SERIAL INTERFACE
FUJITSU SEMICONDUCTOR CONFIDENTIAL
50
4.3.2.
Serial Status Register: SSR
The serial status register (SSR) allows you to check the status of transmission/reception and the reception
error flag as well as to clear the reception error flag.
SSRn(n=0 to 11) : Address Base addr + 02
H
(Access: Byte, Half-word, Word)
7
6
5
4
3
2
1
0
bit
REC Reserved
ES
AWC
ORE
RDRF
TDRE
TBI
0
-
0
0
0
0
1
1
Initial value
R0,W RX,W0 RX,WX RX,WX R,WX
R,WX
R,WX
R,WX
Attribute
Bit name
Function
bit7 REC:
Reception error flag clear
bit
This bit clears ORE flag of the serial status register (SSR).
⋅
To clear an error flag, write "1" to this bit.
⋅
Writing "0" does not affect anything.
A read always results in "0".
bit6 Reserved bit
When read: Reads “0”.
When written: Always write “0”.
bit5 ES:
Endian selection bit
In the cases below, select whether access is made from lower bit of
transmission/reception data or from upper bit.
⋅
Access width for transmission data register (TDR) and reception data
register (RDR) is 16 bits (AWC=0)
⋅
Data length is 20, 24, or 32 bits
⋅
"0" is set: Access from lower bit
⋅
"1" is set: Access from upper bit
Note:
This bit can be changed only if transmission/reception is disabled
(SCR:TXE=RXE=0) and TDR and RDR are empty (SSR:TDRE=1,
SSR:RDRF=0).
bit4 AWC:
Access width control bit
This bit is used to select 16-bit or 32-bit accesses for accessing transmission
data register (TDR) or reception data register (RDR).
⋅
"0" is set: 16-bit access
⋅
"1" is set: 32-bit access
Note:
This bit can be changed only if transmission/reception is disabled
(SCR:TXE=RXE=0) and TDR and RDR are empty (SSR:TDRE=1,
SSR:RDRF=0).
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 SCR:RIE bit are set to "1", a reception interrupt
request will be output.
⋅
If this flag is set, data contained in the receive data register (RDR)
becomes invalid.
⋅
When this flag is set while using the reception FIFO, the reception FIFO
enable bit will be cleared. As a result, the reception data will not be
stored in the reception FIFO.
MB91520 Series
MN705-00010-1v0-E
1363