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8052 Instruction Set
E-9
8052 Instruction Set
DEC Decrement Register
Syntax DEC register
Instructions OpCode Bytes Cycles Flags
DEC A 0x14 1 1 None
DEC direct 0x15 2 1 None
DEC @R0 0x16 1 1 None
DEC @R1 0x17 1 1 None
DEC R0 0x18 1 1 None
DEC R1 0x19 1 1 None
DEC R2 0x1A 1 1 None
DEC R3 0x1B 1 1 None
DEC R4 0x1C 1 1 None
DEC R5 0x1D 1 1 None
DEC R6 0x1E 1 1 None
DEC R7 0x1F 1 1 None
DEC decrements the value of register by 1. If the initial value of register is 0,
decrementing the value causes it to reset to 255 (0xFF
H
).
Note:
The carry flag is not set when the value rolls over from 0 to 255.
See also: INC, SUBB
DIV Divide Accumulator by B
Syntax DIV AB
Instructions OpCode Bytes Cycles Flags
DIV AB 0x84 1 1 C, OV
Divides the unsigned value of the accumulator by the unsigned value of the
B register. The resulting quotient is placed in the accumulator and the
remainder is placed in the B register.
The carry (C) flag is always cleared.
The overflow (OV) flag is set if division by 0 was attempted. Otherwise, it is
cleared.
See also: MUL AB