967 Iterative MAC LATCHUP2026
967 : Iterative MAC LATCHUP2026
- Author: RajuMachupalli
- Description: 32-bit iterative MAC with 7x8-bit multiplier for AI/ML acceleration (LatchUp 2026)
- GitHub repository
- Open in 3D viewer
- Clock: 50000000 Hz
How it works
This design implements a 32-bit multiply-accumulate (MAC) unit for tiny ML accelerators. A 7×8-bit multiplier produces a 15-bit product every clock. A controller FSM shifts partial sums and aligns bias bytes across four training phases (or one phase in inference).
Pin usage
| Signal | Role |
|---|---|
ui_in[6:0] |
Activation (latched while rst_n is low) |
ui_in[7] |
Mode: 0 = inference, 1 = training |
ui_in[7:0] |
Weight byte (operand B) each active cycle |
uio_in[7:0] |
Bias byte (training); uio drives result[23:16] in inference |
uo_out[7:0] |
result[31:24] |
Training FSM
out_th is set when any of product[14:11] are high (large partial product).
Normal path (full cycle):
S0 capture product → S1 → S2 → S3 → S4 finalize → S1
Early exit when out_th is set:
| Current state | Next path |
|---|---|
| S1 | S5 → S6 → S7 → S1 |
| S2 | S6 → S7 → S1 |
| S3 | S7 → S1 |
States S5–S7 use the same bias alignment as S2–S4 but skip the remaining normal phases.
Inference mode
S0 captures the first product, then the FSM holds in S1. Each cycle accumulates {0, product, bias, 0} into sum, shifts result left by 8, and drives uio_out.
How to test
From test/:
make clean && make
Cocotb tests in test/test.py compare the RTL against test/mac_reference.py for:
- Full training cycles (S1→S2→S3→S4→S1)
- All three early-exit paths
- Inference lockstep in S1
- tt07 regression vectors
External hardware
No external hardware is required beyond the Tiny Tapeout carrier. A host MCU can stream weights and bias bytes on the GPIO pins.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | ui_in[0] | uo_out[0] | uio_in[0] |
| 1 | ui_in[1] | uo_out[1] | uio_in[1] |
| 2 | ui_in[2] | uo_out[2] | uio_in[2] |
| 3 | ui_in[3] | uo_out[3] | uio_in[3] |
| 4 | ui_in[4] | uo_out[4] | uio_in[4] |
| 5 | ui_in[5] | uo_out[5] | uio_in[5] |
| 6 | ui_in[6] | uo_out[6] | uio_in[6] |
| 7 | mode | uo_out[7] | uio_in[7] |