HI-82820

The HI-82820 is a silicon gate CMOS device for interfacing the ARINC 429 serial data bus to a 16-bit parallel data bus. It is a form, fit, function drop-in replacement for Holt’s HI-8282 and HI-8282A devices.

Two receivers and an independent transmitter are provided. The receiver input circuitry and logic are designed to meet the ARINC 429 specifications for loading, level detection, timing, and protocol. The transmitter section provides the ARINC 429 communication protocol. Additional interface circuitry such as the Holt HI-8585, HI-8586 or HI-3182 is required to translate the 5-volt logic outputs to ARINC 429 drive levels.

The 16-bit parallel data bus exchanges the 32-bit ARINC data word in two steps when either loading the transmitter or interrogating the receivers. The data bus interfaces with CMOS and TTL.

Timing of all the circuitry begins with the master clock input, CLK. For ARINC 429 applications, the master clock frequency is 1 MHz.

Each independent receiver monitors the data stream with a sampling rate 10 times the data rate. The sampling rate is software-selectable at either 1 MHz or 125 KHz. The results of a parity check are available as the 32nd ARINC bit. The HI-82820 examines the null and data timings and will reject erroneous patterns. For example, with a 125 KHz clock selection, the data frequency must be between 10.4 KHz and 15.6 KHz.

The transmitter has a First In, First Out (FIFO) memory to store 8 ARINC words for transmission. The data rate of the transmitter is software-selectable by dividing the master clock, CLK, by either 10 or 80. The master clock is used to set the timing of the ARINC transmission within the required resolution.