ARINC 629 Multi-Transmitter Bus Terminal Controller

ip/arinc629 is the digital terminal controller for the ARINC 629 multi-transmitter avionics data bus — the arbiter-free TI/SG/TG carrier-sense timers, wordstring TX/RX serdes, and channel filtering that let up to 120 terminals share one 2 Mbps Manchester bus with no central bus controller.

Key Features

• Arbiter-free TI/SG/TG carrier-sense bus access: a 7-state FSM (acc_q) enforces the Transmit Interval floor, the bus-wide Synchronization Gap, and each terminal’s unique Terminal Gap so exactly one terminal transmits per window with no central controller
• Wordstring TX drains the entire TX FIFO back-to-back, generating fresh odd parity into bit 31 of every 32-bit word (odd_parity31); wordstring RX deserializes, checks odd parity, and filters against an 8-entry channel/label accept-list (CHFILT) before storing
• SECDED-protected RX word FIFO (fifo_ecc, 8 deep): single-bit errors corrected transparently, double-bit uncorrectable flagged err_code 2
• Complementary-DMR lockstep across the bus-access, TX-serdes, and RX-serdes FSMs (err_code 9) — the safety-critical addition over a plain serial peripheral, since a single-point flip in the TI/SG/TG sequence could let two terminals transmit at once
• Config-register even parity over EN/LOOPBACK/FILT_EN and the TI/SG/TG timer reloads (err_code 1); RX word odd-parity/framing fault (err_code 3); all latched by the shared safety_monitor
• External Manchester line-coupler boundary at tx_bit/tx_bit_en and rx_bit/rx_bit_en plus a bus_active carrier-sense input — the analog Manchester encode/decode, isolation, and stub network are entirely off-chip
• APB4 register map (4-byte stride): CTRL 0x00, STATUS 0x04, TI 0x08, SG 0x0C, TG 0x10, TXDATA 0x14, RXDATA 0x18, CHFILT 0x1C, IER 0x20, ISR 0x24 (W1C), ERR 0x28 (W1C)

Standards & Compliance

ARINC 629 (Boeing 777 multi-transmitter data bus); DO-254/ED-80 airborne electronic hardware design-assurance framing; ISO 26262 ASIL-B SEooC (SPFM 92.76%, LFM 88.93%, PMHF 5.45×10⁻⁹/h)

Functional Safety

ASIL-B (SEooC) · SPFM 92.76% · LFM 88.93% · PASS

ISO 26262-5 FMEDA method (transferable evidence for the RTCA DO-254 assurance case) · FMEDA available · Safety Manual included

Register Map

Getting Started

// Minimal instantiation
arinc629 #(
 .ADDR_W(6)
) u_arinc629 (
 .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.