Question

Write some PIC code to count how many file registers contain the value 0. Do this by examining each file register (0x00 - 0xff) using indirect addressing. At the end of the code, the W register should contain the count of registers containing 0.

Answer 1

Answer :- The code has been written below-

CountLoop EQU 0x00 ;store value 0 in counter variable
Count1 EQU 0x00 ;store value 0 in counter variable
MOVLW 0x00 ;W = 0
MOVWF FSR ;FSR = 0
Loop1: ;label name Loop1
MOVF INDF, W ;read location value stored in FSR and keep in W, so W = value at the location in FSR
ANDLW 0xFF ;W = W & 0xFF
BTFSC STATUS, 2 ;check if zero flag is clear then skip next statement
GOTO CountZero ;goto label CountZero
Back1:
INCF FSR ;increase the FSR value to next location
INCFSZ CountLoop ;increment the counter, skip next line if zero
GOTO Loop1 ;goto Loop1

Here : GOTO Here ;end of the code

CountZero:
INCF Count1 ;increment the counter value
MOVF Count1, W ;set W = counted zero value
GOTO Back1 ;go to label named as Back1