SAP-2 Logic Instructions

        Logic instructions are digital computer instruction which forms a logical combination (on a bit-by-bit basis) of its operands and leaves the result in a known location.

 

      The following SAP-2 logic instructions are subset of the 8080/8085 instructions.

CMA  

       CMA stands for "complement the accumulator." It inverts each bit in the accumulator, producing the 1's complement.

        Example:

 

Suppose the accumulator contains C2H, and the execution of CMA results in A=3DH.

ANA

       ANA means to AND the accumulator contents with the designated register.  The result is stored in the accumulator, and the two available ANA instructions are ANA B and ANA C.

Figure 1

        Example:

Based on Figure 1, the contents of A and B registers are A7H and D2H, respectively. The execution of AND B will AND accumulator and B register to produce 82H.

ORA

       ORA means OR the accumulator contents with the designated register. The two ORA instructions are ORA B and ORA C.

        Example:

 

For instance, if the accumulator and C register contents are given by Figure 1, then executing ORA C gives A=BFH.

XRA

       XRA means XOR the accumulator contents with the designated register. The two XRA instructions in SAP-2 are XRA B and XRA C.

        Example:

 

If the accumulator and B register contents are given by Figure 1, then the execution of XRA B results in A=75H.

Next topic:

SAP-2 Immediate Logic Instructions 

References:

Brown, J. A., & Malvino, A. P. (1992, 3rd edition). Digital Computer Electronics. Career Education, page 184.

http://encyclopedia2.thefreedictionary.com/logical+instruction