{"id":451,"date":"2026-09-29T09:00:00","date_gmt":"2026-09-29T09:00:00","guid":{"rendered":"https:\/\/jellai.com\/index.php\/2026\/09\/29\/arinc-429-one-transmitter-up-to-twenty-receivers\/"},"modified":"2026-10-15T20:44:00","modified_gmt":"2026-10-15T20:44:00","slug":"arinc-429-one-transmitter-up-to-twenty-receivers","status":"publish","type":"post","link":"https:\/\/jellai.com\/index.php\/2026\/09\/29\/arinc-429-one-transmitter-up-to-twenty-receivers\/","title":{"rendered":"ARINC 429: one transmitter, up to twenty receivers"},"content":{"rendered":"

ARINC 429 has carried data between the line-replaceable units of commercial aircraft since the late 1970s. It grew out of ARINC 419 and the serial interface of the Digital Air Data System, and was first released as ARINC 429-1 in April 1978. Its formal name describes it well: Mark 33 Digital Information Transfer System, a simple, one-way path for digital data.<\/p>\n

One talker, many listeners<\/h2>\n

An ARINC 429 bus is a single shielded twisted pair with a characteristic impedance of 78 Ω, driven by exactly one transmitter and read by one to twenty receivers. Data flows in one direction only; two units that need to talk both ways use two buses, and one unit may have several transmitters and receivers on different buses. The wiring is almost point to point and very reliable: there is no arbitration and no bus master that could fail.<\/p>\n

Plus ten, minus ten, and back to zero<\/h2>\n

The transmitter drives its two wires, A and B, between three levels: HIGH at +10 V, NULL at 0 V and LOW at −10 V. Every bit is a pulse that lasts half the bit time: a 1 swings to +10 V, a 0 to −10 V, and both return to NULL for the second half. Because each bit ends at 0 V, the receivers recover the timing from the signal itself and no clock line is needed. Words are separated by at least four bit times of NULL, and between words the transmitter keeps sending NULL. A bus runs either at high speed, 100 kbit\/s ±1 %, or at low speed, 12 to 14.5 kbit\/s, never both.<\/p>\n

The 32-bit word<\/h2>\n

Everything travels in 32-bit words:<\/p>\n