Tiny Tapeout > Tiny Tapeout Chips > Tiny Tapeout IHP 26a > 744 Hopfield Associative Memory — Odd Digit Recall on 7-Segment
744 Hopfield Associative Memory — Odd Digit Recall on 7-Segment
744 : Hopfield Associative Memory — Odd Digit Recall on 7-Segment
- Author: Shanmukha Mangadahalli Siddaramu
- Description: A 7-node Hopfield associative memory storing two 7-segment display patterns: digit 1 and digit 9. Given a noisy or partial segment pattern on the inputs, the network iterates each clock cycle until it recalls the nearest stored digit. Weights computed analytically via Hebbian learning (W = p1⊗p1 + p9⊗p9). Total gate count ~140 GE. Decimal point lights up when the network converges.
- GitHub repository
- Open in 3D viewer
- Clock: 50000000 Hz
How it works
This design implements a 7-node Hopfield Associative Memory that stores two 7-segment display patterns: digit 1 and digit 9.
A Hopfield network is a recurrent neural network where the weights encode stored
memories directly in silicon — no ROM, no lookup table. Weights are computed
analytically using the Hebbian learning rule: W = p1⊗p1 + p9⊗p9.
Each of the 7 nodes corresponds to one segment (a–g). On every clock cycle the network applies a synchronous update derived from the weight matrix:
new_a = majority(d, f, g) new_e = NAND(b, c)
new_b = c AND NOT e new_f = majority(a, d, g)
new_c = b AND NOT e new_g = majority(a, d, f)
new_d = majority(a, f, g)
The decimal point (uo_out[7]) lights up when the network has converged.
Total gate count: ~140 GE.
Stored patterns:
| Digit | Segments | Hex |
|---|---|---|
| 1 | b, c | 0x06 |
| 9 | a,b,c,d,f,g | 0x6F |
Safe to corrupt (majority-vote protected): segments a, d, f, g
Fragile (mutually dependent): segments b, c, e
How to test
- Set
ui_in[6:0]DIP switches to a segment pattern - Pulse
uio_in[0]high for one clock cycle (start) - Watch display update — decimal point lights when settled
| Input | Expected output |
|---|---|
0x06 |
Digit 1 |
0x6F |
Digit 9 |
0x07 (digit 1 + seg-a) |
Digit 1 corrected |
0x6E (digit 9 − seg-a) |
Digit 9 corrected |
0x67 (digit 9 − seg-d) |
Digit 9 corrected |
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | seg-a: top horizontal segment | seg-a: recalled top horizontal | start: pulse high 1 cycle to load input and begin recall |
| 1 | seg-b: top-right vertical segment | seg-b: recalled top-right | |
| 2 | seg-c: bottom-right vertical segment | seg-c: recalled bottom-right | |
| 3 | seg-d: bottom horizontal segment | seg-d: recalled bottom horizontal | |
| 4 | seg-e: bottom-left vertical segment | seg-e: recalled bottom-left | |
| 5 | seg-f: top-left vertical segment | seg-f: recalled top-left | |
| 6 | seg-g: middle horizontal segment | seg-g: recalled middle | |
| 7 | dp: decimal point — high when network has converged |