Registers - Toshiba TLCS-90 Series Data Book

TOSHIBA TMP90C840
3.1.2 Registers
Fig. 3.1 (2) shows the configuration of registers.
7 0
I _ _
~
_ _
-+-_ _
~
_ _
I
I I
I I
I I
3 0 15 0
Fig. 3.1 (2) Configuration of Registers
Main registers
Alternative
registers
Special purpose
registers
The TMP90C840 uses main registers, alternative registers and dedicated
registers. The main registers and the alternative registers are
allowed to be exchanged of their contents by a register exchange
instruction.
(1) Register A
This is an 8-bit register used mainly for 8-bit arithmetic and logic
operations.
(2) Register F
This is an 8-bit register that stores the status of operation results.
Configuration of register F is shown in Fig. 3.1 (3).
7
6 5 4 3 2
1
o
MSB I S I Z IIFFI H I X Ip/vl N I C I LSB
Fig. 3.1 (3) Configuration of Register F
o Sign flag (S)
The sign flag is set to "1" when the arithmetic result is negative.
It stores the contents of the most significant bit (MSB) of the
arithmetic and logic unit (ALU).
o Zero flag (Z)
Z flag is set to "I" when the all bits of the ALU after operation are
"0".
MPU90-10