HD6433308 Datasheet, PDF (200/349 Pages) Hitachi Semiconductor – Hitachi Single-Chip MicroComputer

9.2.7 Serial Status Register (SSR) – H’FFDC
Bit
7
6
5
4
3
2
1
0
TDRE RDRF ORER FER PER
—
—
—
Initial value
1
0
0
0
0
1
1
1
Read/Write R/(W)* R/(W)* R/(W)* R/(W)* R/(W)* —
—
—
* Software can write a “0” to clear the flags, but cannot write a “1” in these bits.
The SSR is an 8-bit register that indicates transmit and receive status. It is initialized to H’87 at a
reset and in the standby modes.
Bit 7 – Transmit Data Register Empty (TDRE): This bit indicates when the TDR contents have
been transferred to the TSR and the next character can safely be written in the TDR.
Bit 7
TDRE
0
1
Description
To clear TDRE, the CPU must read TDRE after it has been set to "1," then write a “0”
in this bit.
This bit is set to 1 at the following times:
(Initial value)
(1) When TDR contents are transferred to the TSR.
(2) When the TE bit in the SCR is cleared to "0."
Bit 6 – Receive Data Register Full (RDRF): This bit indicates when one character has been
received and transferred to the RDR.
Bit 6
RDRF
0
1
Description
To clear RDRF, the CPU must read RDRF after
it has been set to "1," then write a “0” in this bit.
This bit is set to 1 when one character is received without error and
transferred from the RSR to the RDR.
(Initial value)
187