Serial Status Register (Ssr) - Hitachi H8/3035 Series Hardware Manual

11.2.7 Serial Status Register (SSR)

SSR is an 8-bit register containing multiprocessor bit values, and status flags that indicate the
SCI operating status.
Bit 7
TDRE
Initial value 1
Read/Write R/(W)
*
Transmit data register empty
Status flag indicating that transmit data has been transferred from TDR into
TSR and new data can be written in TDR
Note: Only 0 can be written, to clear the flag.
*
The CPU can always read and write SSR, but cannot write 1 in the TDRE, RDRF, ORER, PER,
and FER flags. These flags can be cleared to 0 only if they have first been read while set to 1.
The TEND and MPB flags are read-only bits that cannot be written.
SSR is initialized to H'84 by a reset and in standby mode.
6 5 4
RDRF ORER FER
0 0 0
R/(W) R/(W) R/(W)
* *
Framing error
Status flag indicating detection of a receive
framing error
Overrun error
Status flag indicating detection of a receive overrun error
Receive data register full
Status flag indicating that data has been received and stored in RDR
3 2
PER TEND MPB
0 1
R/(W) R
* *
Multiprocessor bit
Stores the received
multiprocessor bit value
Transmit end
Status flag indicating end of
transmission
Parity error
Status flag indicating detection of
a receive parity error
1 0
MPBT
0 0
R R/W
Multiprocessor
bit transfer
Value of multi-
processor bit to
be transmitted
301