ALU Flag Evaluation Branch Logic
Instruction decode units in microprocessors rely on ALU status flags to determine whether conditional branches should be taken. The branch unit evaluates combinations of these flags to resolve complex conditions like the signed "Greater Than Or Equal" (BGE) instruction.
Construct the branch evaluation logic for a BGE instruction. The circuit receives the Zero (Z), Negative (N), and Overflow (V) flags from an ALU that just evaluated A - B. The output Y must assert if A >= B in signed two's complement arithmetic.
| Z | N | V | Y | |-----|-----|-----|-----| | 0 | 0 | 0 | 1 | | 0 | 0 | 1 | 0 | | 0 | 1 | 0 | 0 | | 0 | 1 | 1 | 1 | | 1 | 0 | 0 | 1 | | 1 | 0 | 1 | 0 | | 1 | 1 | 0 | 0 | | 1 | 1 | 1 | 1 |
Constraints
- Combinational logic only.
- Do not use high-level arithmetic or comparison blocks.
- Drive the output
Ystrictly based on the provided truth table.
Topics
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