Guides / ALU operations in assembly

Step 2 of 5

Add and subtract with ADDWF / SUBWF

Goal

Add PORTB + PORTD and display on LATC.

MOVF PORTB, W loads operand A. ADDWF PORTD, W adds B (to W) or ADDWF PORTD, F adds in place. For subtract: SUBWF (watch minuend order).

					        MOVF    PORTB, W
        ADDWF   PORTD, W
        MOVWF   LATC
				

Try it

Implement A - B and turn on RB0 if the result is negative (borrow).

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