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ADC Instruction

Concept

The ADC (Add with Carry) instruction is an arithmetic operation commonly found in ALU instruction sets. In the modeled context, it computes A = A + operand + Cin (carry-in), storing the result back in register A and updating the processor's flag register accordingly.

First seen 6/20/2026
Last seen 6/20/2026
Evidence 2 chunks
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WIKI

Overview

The ADC instruction (Add with Carry) is an ALU arithmetic operation. In the documented processor model, it is executed by invoking the executeALUInstruction(byte instr) task with the corresponding opcode (for example, ADC H is encoded as 8'h8C).

The semantic effect of an ADC H instruction is to compute:

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RELATIONSHIPS

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executeALUInstruction ← uses 97% 2e
The executeALUInstruction task is used to execute the ADC H instruction in the test program.
ALU Instruction part of → 95% 2e
The ADC instruction is one specific ALU instruction executed by the model.

CITATIONS

4 sources
4 citations — click to collapse
[1] The ADC instruction computes A = A + operand + Cin, combining the operand with the current carry flag value. Golden reference
[2] The opcode for ADC H in the model is 0x8C and is dispatched via the executeALUInstruction(byte instr) task. Golden reference
[3] ADC sets the zero flag F(3) if the result is 0x00, clears the subtract flag F(2), sets the half-carry flag F(1) on lower-to-higher nibble carry, and sets the carry flag F(0) on overflow. Golden reference
[4] Executing ADC H four times with H=5 starting from A=0 causes A to reach 20 (0x14), with the lower-to-higher nibble overflow reflected in F(1) on the fourth execution. Golden reference