CHI Home Node — Multi-Outstanding Memory Path (HN-F)

What it is

chi_hn_f_mo is a synthesizable SystemVerilog CHI Home Node bandwidth tier: it handles only the two non-coherent (“NoSnp”) AMBA 5 CHI opcodes — ReadNoSnp and WriteNoSnp — but pipelines the reads.

Key Features

• Non-coherent-only opcode set — ReadNoSnp (6’h04) / WriteNoSnp (6’h1D) — no directory, no snoop channels, no coherence state to maintain
• Tagged, multi-outstanding read engine: N_OUT-deep outstanding table (default 4) with lowest-free-slot allocation; returning mem_rtxnid demultiplexes replies that may complete out of issue order
• 1-deep completion skid backpressures the SN-F (mem_rready = !cmp_val || txdat_acc) whenever the CHI-side TXDAT drain stalls — the SN-F adapter must hold its return, not drop it
• Single-outstanding write engine (DBIDResp → RXDAT data → SN-F store → Comp) sharing the one mem_req line with new reads by construction, not arbitration
• Inline per-64-bit SECDED (ecc_pkg) on the held read-completion line: single-bit upset corrected before CompData is driven, double-bit flagged uncorrectable (err_code 2)
• SN-F read error (mem_rerr) captured PER completion and surfaced both as a fault and as a CHI RespErr (DataError) on that read’s own CompData — never mis-attributed to a later read (err_code 3)
• ASIL-B: config/address parity (err_code 1), read-completion SECDED (err_code 2), outstanding-transaction watchdog (err_code 4), write-FSM diverse-DMR shadow (err_code 9); formal proves the tag-routing invariant (a_tag_val) and covers ≥2 simultaneously outstanding reads (c_multi)

Standards & Compliance

Arm AMBA 5 CHI (Issue E); ISO 26262 ASIL-B SEooC

Functional Safety

ASIL-B (SEooC) · SPFM 90.90% · LFM 89.65% · PASS

ISO 26262:2018 · FMEDA available · Safety Manual included

Register Map

See datasheet for full register reference.

Getting Started

// Minimal instantiation
chi_hn_f_mo #(
 .ADDR_W(6)
) u_chi_hn_f_mo (
 .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.