A simple 1-digit BCD (Binary-Coded Decimal) adder implemented using only basic logic gates (XOR, AND, OR), toggle switches, and green LEDs. This project is designed to demonstrate how BCD addition and correction work at the gate level.
- Adds two 1-digit BCD numbers (0–9)
- Uses basic gates only (no ICs or microcontrollers)
- Implements BCD correction (adds 6 when needed)
- Displays output using green LEDs
- Inputs provided via toggle switches
- XOR gates
- AND gates
- OR gates
- Ground (GND)
- Toggle switches (8 total for 2 BCD inputs)
- Green LEDs (for 4-bit sum output and carry)
- Inputs: Two BCD digits (A and B), each 4 bits wide (valid range: 0000 to 1001).
- Binary Addition: Basic full adder logic adds the inputs.
- BCD Correction: If the sum exceeds 9 (1001), the circuit adds
0110(decimal 6) to correct it. - Output: Corrected 4-bit BCD sum shown on LEDs. If there's a carry, it's indicated by an additional LED.
⚠️ Note: Inputs must be valid BCD (0–9). Invalid inputs (like 1010–1111) may cause incorrect results.
This section shows three test cases of 1-digit BCD addition simulated using Proteus.
- Binary:
0011 + 0100 = 0111 - BCD Result:
0111(7) - ✅ No correction needed as sum ≤ 9.
- Binary:
0101 + 0100 = 1001 - BCD Result:
1001(9) - ✅ Still within valid BCD range, so no correction needed.
- Binary sum:
0101 + 1000 = 1101→ decimal 13 - 13 is invalid in BCD, so we add
0110(6) to correct it. - Corrected sum:
1101 + 0110 = 1 0011→ BCD Output:0001 0011(13) - ✅ Carry = 1 (1)2 , Sum = 3 (0011)2
This project is for educational purposes. Feel free to use, modify, and build upon it.