Decrement f, Skip if 0
The contents of register ‘f’ are decremented. If ‘d’ is ‘0’, the result is placed in the W register. If ‘d’ is ‘1’, the result is placed back in register ‘f’. If the result is ‘1’, the next instruction is executed. If the result is ‘0’, then a NOP is executed instead, making it a 2 TCY instruction.
[the_ad id=”3059″]Syntax:
[ label ] DECFSZ f,d
Operation:
(f) – 1 → (destination);
skip if result = 0
Operands:
- f is from 0 to 127 (decimal)
- d can be either 0 or 1
Status Affected: None
Example:
DECFSZ REG,0 GOTO SUB1 GOTO SUB2
Before instruction:
REG = 0x0A W = 0x01
After instruction:
REG = 0x0A W = 0x09
The result is not zero, therefore, the line GOTO SUB1 is read.
[the_ad id=”3059″]Example:
DECFSZ REG,1 GOTO SUB1 GOTO SUB2
Before instruction:
REG = 0x01 W = 0x01
After instruction:
REG = 0x00 W = 0x01
The result is zero, hence the line GOTO SUB1 is skipped and the program jumps to GOTO SUB2.
