Block diagram
Physical implementation
What you’re licensing
A hardware counting Bloom filter for line-rate set-membership screening — ID filtering, allowlist/denylist checks… It is delivered as a licensable soft-IP block engineered as an ASIL-B Safety Element out of Context — not just RTL, but the complete functional-safety work package needed to carry it into an ISO 26262 program:
bloom_filter is a synthesizable, ASIL-B counting Bloom filter soft-IP: a compact, self-checking, line-rate set-membership screen — a fast “have I seen this key before” pre-filter for ID filtering, allowlist/denylist checks, dedup, and cache/flow lookups — with deletion support and a hardware guarantee of no false negatives (until a counter saturates).
Key Features
- Counting Bloom filter: insert/query/delete over AXI4-Stream, bounded false-positive rate, no false negatives until a counter saturates — the property a line-rate ID/allowlist screen needs
- Double-hashing (Kirsch-Mitzenmacher): K probe indices from two multiply-shift base hashes, only two multipliers regardless of K, proven FPR-equivalent to K independent hashes
- Deletion with saturation-freeze: a maxed-out counter (CNT_W-bit) is skipped on DELETE so it can never be pushed to a false negative
- APB4-lite CSR (SEED0/SEED1 hash seeds, CTRL.CLEAR, STATUS, OCCUPANCY fill estimate) kept fully separate from the AXI4-Stream data plane — no key ever crosses the config bus
- 32-bit SECDED on the counter table: single-bit upsets corrected and scrubbed on every probe, double-bit errors flagged err_code 2
- Diverse DMR across the hash/index datapath, the present/min_count result, and a complementary-shadow control FSM — the answer to a fault-free algorithmic check the filter cannot run — err_code 9; even parity on the hash-seed config, err_code 1
- FMEDA (pre-sign-off engineering numbers): SPFM 90.90%, LFM 90.00%, PMHF 4.21×10⁻⁸/h — PASS vs the ASIL-B target
Standards & Compliance
AMBA APB4-lite, AMBA AXI4-Stream; ISO 26262 ASIL-B SEooC (SPFM 90.90%, LFM 90.00%, PMHF 4.21×10⁻⁸/h, pre-sign-off engineering FMEDA)
Functional Safety
ASIL-B (SEooC) · SPFM 90.90% · LFM 90.00% · PASS
ISO 26262:2018 · FMEDA available · Safety Manual included
Register Map
| Offset | Register | Description |
|---|---|---|
0x00 | CTRL | RW [0]=CLEAR (self-clearing; sweeps the whole table to empty) |
0x04 | STATUS | RO [0]=BUSY, [1]=OP_DONE(sticky), [2]=ERR_VALID, [6:3]=ERR_CODE |
0x08 | OCCUPANCY | RO running net insert count since reset/clear (fill estimate, saturating) |
0x0C | SEED0 | RW [31:0] multiply-shift constant A1 for base hash h1 (odd recommended) |
0x10 | SEED1 | RW [31:0] multiply-shift constant A2 for base hash h2 (forced odd internally) |
…1 more registers — see datasheet for the full table.
Getting Started
// Minimal instantiation
bloom_filter #(
.ADDR_W(6)
) u_bloom_filter (
.clk (clk),
.rst_n (rst_n),
// APB4
.p_paddr (paddr),
.p_psel (psel),
.p_penable (penable),
.p_pwrite (pwrite),
.p_pwdata (pwdata),
.p_prdata (prdata),
.p_pready (pready),
// Safety
.err_clear (1'b0),
.err_valid (err_valid),
.err_code (err_code)
);Configure via the CTRL register after reset to enable the IP and set operating parameters. Monitor err_valid / err_code for any safety faults reported by the built-in safety monitor.
Where it fits
Typically deployed in specialized datapath and acceleration needs across the portfolio.
Why license it, not build it
Interested in Counting Bloom Filter?
Pricing, the per-IP FMEDA, safety manual, and RTL data room are shared under a mutual NDA.
Figures are pre-silicon engineering-grade estimates for a Safety Element out of Context (SEooC); final ASIL sign-off is the integrator’s, supported under NDA. FMEDA and Safety Manual available under NDA.
circuit-design.space · +1-971-357-1400 · anovickis@circuit-design.space