Holt Integrated Circuits, a world leader in data bus IC’s for commercial and military avionics, introduced a fully integrated single chip ARINC 717 Bus Protocol Controller IC, the HI-3717. The HI-3717 communicates with an external microcontroller via a 4-wire Serial Peripheral host Interface (SPI) and provides selectable Harvard Bi-Phase (HBP) and Bi-Polar Return-to-Zero (BPRZ) channels with encoders/decoder and dedicated line drivers and line receivers for direct connection to the ARINC 717 bus. The device is targeted at digital flight data recorder applications and may be used in the recorder itself, the data acquisition unit or the quick access recorder.

The HI-3717 includes an on-chip DC/DC converter, requiring only a single 3.3V supply to operate. All voltage levels necessary for the BPRZ and HBP channels are generated on-chip. There are 9 programmable bit rates, corresponding to 32, 64, 128, 256, 512, 1024, 2048, 4096 and 8192 words/sec. The receive and transmit channels both have 32-bit x 12 word FIFOs, allowing the external host to take a “hands off” approach and perform other tasks without the need for frequent buffer servicing. Dedicated FIFO status flags are provided in both registers and external pins. Additional features include programmable slew rates on the transmitters (1.5µs, 7.5µs and 10µs), dedicated SPI instruction set, digital transmitter outputs and frame / subframe word count indicator.

The HI-3717 uses a proprietary synchronization method which guarantees the part will rapidly attain correct synchronization, even if additional or false sync words are embedded in the data stream. If a device loses synchronization for any reason, it will automatically restart the synchronization process and immediately try to re-acquire sync. Three modes of operation are possible. The first, Flight Mode, is the default, which requires detection of all four consecutive sync words in the correct order and time. The second mode, Test Mode, will declare sync when any two consecutive sync words are detected and finally a third mode allows synchronization to be turned off, allowing all received data to be stored in the receive FIFO. The three modes provide maximum flexibility for both in-flight and test equipment applications.