N-Port CHI Coherent Interconnect

Catalog #MC-fabric · ASIL-B SEooC

Parameterized N-port AMBA 5 CHI coherent interconnect: arbitrates N caching Request Nodes (RN-F) into one CHI Home Node (HN-F) and routes the Home Node’s snoops, completions, and read data back to the correct requester by target id.

Key Features

• N-way rotating-priority REQ arbitration: scans (last_grant + k) mod N for k=1..N so priority rotates through every port — proven reachable by the c_arbN cover (the highest-index RN wins arbitration at least once)
• tgtid-demultiplexed return path: the low log2(N) bits of the HN’s tgtid select the destination RN through an index-compare generate loop — one rn_rxsnp/rxrsp/rxdat[g] can assert per cycle, by construction
• Lowest-index-wins mux of write-data and snoop-response uplinks into the single-outstanding Home Node, inherited from the 2-port chi_fabric_ic’s single-active-driver assumption
• Zero internal error-reporting surface: no err_valid/err_code, no config register — a mis-routed flit is caught at the endpoint that consumes it (HN parity/SECDED, or the RN’s own txnid-mismatch drop + timeout watchdog, err_code 4)
• RN-to-RN isolation formally proven for the parametric width: a_grant_1hot, a_snoop_1hot, a_rsp_1hot, a_dat_1hot, a_snoop_route, a_srcid_bound (formal/chi_fabric_icn.sby); vacuity-audited vacuity-clean (3/3 covers reached)
• Single synchronous clock domain (clk/rst_n only) — no CDC in this block; scales to any N at synthesis time via packed-array rn_* ports and generate loops
• Catalog FMEDA at the synthesized N=4 default (1233 cells): SPFM 90.00%, LFM 90.00%, PMHF 2.72×10⁻⁹/h, PASS ASIL-B

Standards & Compliance

Arm AMBA 5 CHI (Issue E-class); ISO 26262 ASIL-B SEooC (SPFM 90.00%, LFM 90.00%, PMHF 2.72×10⁻⁹/h)

Functional Safety

ASIL-B (SEooC) · SPFM 90.00% · LFM 90.00% · PASS

ISO 26262:2018 · FMEDA available · Safety Manual included

Register Map

See datasheet for full register reference.

Getting Started

// Minimal instantiation
chi_fabric_icn #(
  .ADDR_W(6)
) u_chi_fabric_icn (
  .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.