Logic Function Instructions - Microchip PIC microcontroller

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Logic Function Instructions

The next instructions set is the Logic Function instructions. Within this set, there are instructions to perform the typical logic functions such as OR, AND, XOR etc. Here is the list of them:

Instruction	Description
ANDLW k	Logic AND between the contents of W and the literal value k. The results is stored back to W.
ANDWF f , d	Logic AND between the content of W register with the content of a file register 'f'. If d is 0 the result is stored in the W register, if d is 1 the result is stored back to the file register 'f'.
IORLW k	Logic OR between the contents of W and the literal value k. The results is stored back to W.
IORWF f , d	Logic OR between the content of W register from the content of a file register 'f'. If d is 0 the result is stored in the W register, if d is 1 the result is stored back to the file register 'f'.
XORLW k	Logic EXCLUSIVE OR between the contents of W and the literal value k. The results is stored back to W.
XORWF f , d	Logic EXCLUSIVE OR between the content of W register from the content of a file register 'f'. If d is 0 the result is stored in the W register, if d is 1 the result is stored back to the file register 'f'.

Now, let's see the instructions one by one:

ANDLW k

With this instructions you perform an AND logic function between the W register and the literal value k. The result is stored back to the W register. The status affected from this function are:

Z - Zero

The logic operation performed is:

W = W +.AND. f
Where 0 <= k <= 255

Example

        movlw b'10000100'   ;The W register has now the binary value '10000100'
        andlw b'00001111'   ;The binary value '00001111' AND with the W register.
                            ;Now the W register has the binary value '00000100'

ANDWF f , d

With this instructions you perform an AND logic function between the W register and the file register 'f'. If d is 0 the result is stored in the W register, if d is 1 the result is stored back to the file register. The status affected from this function are:

Z - Zero

The logic operation performed is:

Destination (d) = W .AND. f
Where 0 <= f <= 127

Example

;This example requires that you have declare a file register for example
;TempRegister          equ 0x20
        movlw b'10000100'      ;The W register has the value '10000100'
        movwf TempRegister     ;The TempRegister has now the value '10000100'
        movlw d'00001111'      ;The W register has the value '00001111'
        andwf TempRegister,1   ;The W register AND with the contents of TempRegister 
                               ;and the result ('00000100') is stored to TempRegister

IORLW k

With this instructions you perform an OR logic function between the W register and the literal value k. The result is stored back to the W register. The status affected from this function are:

Z - Zero

The logic operation performed is:

W = W +.OR. f
Where 0 <= k <= 255

Example

        movlw b'10000100'   ;The W register has now the binary value '10000100'
        iorlw d'00001111'   ;The binary value '00000011' OR with the W register.
                            ;Now the W register has the binary value '10001111'

IORWF f , d

With this instructions you perform an OR logic function between the W register and the file register 'f'. If d is 0 the result is stored in the W register, if d is 1 the result is stored back to the file register. The status affected from this function are:

Z - Zero

The logic operation performed is:

Destination (d) = W .OR. f
Where 0 <= f <= 127

Example

;This example requires that you have declare a file register for example
;TempRegister          equ 0x20
        movlw b'10000100'      ;The W register has the value '10000100'
        movwf TempRegister     ;The TempRegister has now the value '10000100'
        movlw d'00001111'      ;The W register has the value '00001111'
        iorwf TempRegister,1   ;The W register OR with the contents of TempRegister 
                               ;and the result ('10001111') is stored to TempRegister

XORLW k

With this instructions you perform an EXCLUSIVE OR logic function between the W register and the literal value k. The result is stored back to the W register. The status affected from this function are:

Z - Zero

The logic operation performed is:

W = W +.XOR. f
Where 0 <= k <= 255

Example

        movlw b'10000100'   ;The W register has now the binary value '10000100'
        xorlw d'00001111'   ;The binary value '00000011' XOR with the W register.
                            ;Now the W register has the binary value '10001011'

XORWF f , d

With this instructions you perform an EXCLUSIVE OR logic function between the W register and the file register 'f'. If d is 0 the result is stored in the W register, if d is 1 the result is stored back to the file register. The status affected from this function are:

Z - Zero

The logic operation performed is:

Destination (d) = W .XOR. f
Where 0 <= f <= 127

Example

;This example requires that you have declare a file register for example
;TempRegister          equ 0x20
        movlw b'10000100'      ;The W register has the value '10000100'
        movwf TempRegister     ;The TempRegister has now the value '10000100'
        movlw d'00001111'      ;The W register has the value '00001111'
        xorwf TempRegister,1   ;The W register OR with the contents of TempRegister 
                               ;and the result ('10001011') is stored to TempRegister

The Logic Functions Table

Here is a final tip for you. The following table demonstrates the result for the above functions between two bits.

Bit 1	Bit 2	AND	OR	XOR
0	0	0	0	0
0	1	0	1	1
1	0	0	1	1
1	1	1	1	0

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Comments

At 23 February 2011, 20:06:32 user Kammenos wrote: [reply @ Kammenos]

capn than you for the correction. I pressed 'd' instead of 'b'. 'd' stands for decimal but i declare a binary...

At 23 February 2011, 17:04:03 user capn wrote: [reply @ capn]

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