Debug a Full Subtractor with Wrong Borrow Expression
A full subtractor performs multi-bit subtraction by computing the difference and borrow-out of two 1-bit inputs and a previous borrow-in.
Expected behavior:
| A | B | Bin | Diff | Bout | |-----|-----|-------|--------|--------| | 0 | 0 | 0 | 0 | 0 | | 0 | 0 | 1 | 1 | 1 | | 0 | 1 | 0 | 1 | 1 | | 0 | 1 | 1 | 0 | 1 | | 1 | 0 | 0 | 1 | 0 | | 1 | 0 | 1 | 0 | 0 | | 1 | 1 | 0 | 0 | 0 | | 1 | 1 | 1 | 1 | 1 |
Simulation shows Bout = 0 for inputs A=0, B=1, Bin=0. The borrow output is incorrect under specific conditions. Inspect the circuit and correct the fault.
Constraints
- The circuit must correctly implement the full subtractor truth table.
- Do not modify the logic path generating the
Diffoutput. - Use standard basic logic gates (AND, OR, NOT, XOR).
Topics
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