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;==================================================================== ; subroutine ADD16 ; 16-Bit Signed (2's Complement) Addition ; input: r1, r0 = X ; r3, r2 = Y ; output: r1, r0 = signed sum S = X + Y ; Carry C is set if the result (S) is out of range ; alters: acc, C, OV ;====================================================================
ADD16: anl PSW, #0E7H ; Register Bank 0 mov a, r0 ; load X low byte into acc add a, r2 ; add Y low byte mov r0, a ; put result in Z low byte mov a, r1 ; load X high byte into acc addc a, r3 ; add Y high byte with carry mov r1, a ; save result in Z high byte mov C, OV ret
;====================================================================; subroutine ADD32; 32-Bit Signed (2's Complement) Addition;; input: r3, r2, r1, r0 = X; r7, r6, r5, r4 = Y;; output: r3, r2, r1, r0 = signed sum S = X + Y; Carry C is set if the result (S) is out of range;; alters: acc, C, OV;====================================================================
ADD32: anl PSW, #0E7H ; Register Bank 0 mov a, r0 ; load X low byte into acc add a, r4 ; add Y low byte mov r0, a ; save result mov a, r1 ; load X next byte into acc addc a, r5 ; add Y next byte with carry mov r1, a ; save result mov a, r2 ; load X next byte into acc addc a, r6 ; add Y next byte mov r2, a ; save result mov a, r3 ; load X high byte into acc addc a, r7 ; add Y high byte with carry mov r3, a mov C, OV ret