7. Serial status register (SSR)
Bit
7
6
RDRF
0
5
OER
0
4
FER
0
3
PER
0
2
TEND
1
1
MPBR
0
0
MPBT
0
TDRE
1
Initial value
Read/Write
*
*
*
*
*
R/(W)
R/(W)
R/(W)
R/(W)
R/(W)
R
R
R/W
Note:
*
Only a write of 0 for flag clearing is possible.
SSR is an 8-bit register containing status flags that indicate the operational status of SCI3, and
multiprocessor bits.
SSR can be read or written by the CPU at any time, but only a write of 1 is possible to bits TDRE,
RDRF, OER, PER, and FER. In order to clear these bits by writing 0, 1 must first be read.
Bits TEND and MPBR are read-only bits, and cannot be modified.
SSR is initialized to H'84 upon reset, and in standby, module standby, or watch mode.
Bit 7: Transmit data register empty (TDRE)
Bit 7 indicates that transmit data has been transferred from TDR to TSR.
Bit 7
TDRE
Description
0
Transmit data written in TDR has not been transferred to TSR
Clearing conditions:
After reading TDRE = 1, cleared by writing 0 to TDRE
When data is written to TDR by an instruction
1
Transmit data has not been written to TDR, or transmit data written in
TDR has been transferred to TSR
Setting conditions:
When bit TE in SCR3 is cleared to 0
When data is transferred from TDR to TSR
(initial value)
279
ETC [ ETC ]
