HI-85990

The HI-85990 from Holt Integrated Circuits is a silicon gate CMOS device for interfacing a 16-bit parallel data bus directly to the ARINC 429 serial bus. It is a form, fit, function drop-in replacement for Holt’s HI-8599. This device provides two receivers, an independent transmitter and line driver capability in a single package. 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 and the line driver circuits provide the ARINC 429 output 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.

The HI-85990 provides the option to bypass most of the internal output resistance so that external series resistance may be added for lighting protection and still match the 75 ohm characteristic impedance of the ARINC bus.

Each independent receiver monitors the data stream with a sampling rate 10 times the data rate. The sampling rate is software selectable at either 1MHz or 125KHz. The results of a parity check are available as the 32nd ARINC bit. The HI-85990 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.