Tiny Tapeout > Tiny Tapeout Chips > Tiny Tapeout SKY 26a > 865 IEEE Open Silicon 2026: UTB Logic Trivia Challenge: 8-bit Digital Lock
865 IEEE Open Silicon 2026: UTB Logic Trivia Challenge: 8-bit Digital Lock
865 : IEEE Open Silicon 2026: UTB Logic Trivia Challenge: 8-bit Digital Lock
- Author: George Archbold, Junior Sarmiento, Daniela Gonzalez, Miguel Baranoa, Jorge Mercado, Samuel Meza
- Description: 8-bit Pattern Comparator that functions as a digital lock
- GitHub repository
- Open in 3D viewer
- View in Wokwi
- Clock: 0 Hz
How it works
This project implements an 8-bit Pattern Comparator that functions as a digital lock. The circuit acts as a judge, validating whether the user has entered the correct "Master Key" via an external 8-bit DIP switch.
Internal Logic Architecture: To ensure a robust and educational design, the IC utilizes a bit-matching architecture:
- Key Definition: A specific 8-bit sequence is hard-coded into the silicon (10110101).
- Bit-Wise Inversion: For every input bit where the master key requires a '0', an internal NOT gate (inverter) is placed. For bits requiring a '1', the signal is routed directly.
- The Super-AND Validator: All eight signals (inverted and direct) are fed into a high-order 8-input AND gate tree (constructed from a cascade of 2-input standard AND gates).
- Final Result:
- Success: If the input perfectly matches the master key, the final AND gate outputs a logic '1', lighting up the Green LED.
- Failure: If even a single bit differs, the output remains '0', triggering a Red LED via an additional inverter.
Logic Table for the master key: The circuit is programmed to recognize the following binary pattern (from MSB to LSB):
| Pin | Bit Weight | Key Value | Internal Logic |
|---|---|---|---|
| ui_in[7] | MSB (128) | 1 | Direct Wire |
| ui_in[6] | 64 | 0 | NOT Gate |
| ui_in[5] | 32 | 1 | Direct Wire |
| ui_in[4] | 16 | 1 | Direct Wire |
| ui_in[3] | 8 | 0 | NOT Gate |
| ui_in[2] | 4 | 1 | Direct Wire |
| ui_in[1] | 2 | 0 | NOT Gate |
| ui_in[0] | LSB (1) | 1 | Direct Wire |
How to test
- Power Up: Ensure the chip is powered and the ena (enable) pin is high.
- Initial State: Set all DIP switches to '0'. The Red LED (uo_out[1]) should be ON, indicating an incorrect code.
- Entering the Code: Toggle the switches to match the secret key. Note that the physical switches on a standard Wokwi/PMOD block are usually ordered from ui_in[0] (Left) to ui_in[7] (Right). To enter the key 10110101 (MSB to LSB), set the switches to: 1 0 1 0 1 1 0 1 (Left to Right).
- Verification: Once the correct pattern is set, the Green LED (uo_out[0]) will turn ON, and the Red LED will turn OFF.
External hardware
- 8-Position DIP Switch: Connected to the input bus ui_in[7:0].
- Green LED: Connected to uo_out[0] (Success indicator).
- Red LED: Connected to uo_out[1] (Failure indicator).
- Resistors: Two 220Ω resistors for the LEDs or your resistors values.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | bit1_LSB | LED_OK | |
| 1 | bit2 | LED_NOT_OK | |
| 2 | bit3 | ||
| 3 | bit4 | ||
| 4 | bit5 | ||
| 5 | bit6 | ||
| 6 | bit7 | ||
| 7 | bit8_MSB |