ADVANCED VEHICLE TECHNOLOGIES, Inc.
Press Release
31 October, 1996

AVT-921 Dual J1850 Interface

Advanced Vehicle Technologies, Inc. announces its latest J1850 compatible product. The AVT-921 is a Dual J1850 Interface (VPW and PWM) designed to allow a PC/AT compatible computer to be connected to and communicate with a J1850 bus equipped automobile.

Society of Automotive Engineers (SAE) J1850 is a two part standard for an in-vehicle multiplex bus. J1850 buses are designed to allow the various sensors, actuators, and controllers found in today’s automobiles to communicate. Additionally, external test equipment can access the bus for diagnostics and other maintenance purposes. The standard has been specified in a number of Federal and State regulations (sometimes referred to as OBD-II for On-Board Diagnostics, phase 2). Automobile manufacturers have begun implementing the standard in many vehicles and its use will become more widespread.

The J1850 standard is an open specification, unlike the proprietary methods car manufacturers have used previously. However, system designers and manufacturers have been given considerable leeway in adopting and implementing the standard. A J1850 compliant multiplex bus may exist in either of two incompatible forms: VPW (Variable Pulse Width modulation) with an average bit rate of 10.4 kbps or PWM (Pulse Width Modulation) with an average bit rate of 41.6 kbps.

The AVT-921 addresses this issue by providing both a VPW and a PWM interface on one board. Functionally, the AVT-921 acts as a protocol translator and message buffer between the controlling PC and the vehicle J1850 bus. Mode selection is made via a software command. When in VPW mode the board supports transmit and receive operations at 4 times the normal rate (4X mode) that may be required for some GM diagnostic functions.

The AVT-921 is a 3/4 length, 8-bit ISA compatible board designed for installation in a PC/AT compatible host computer. The board is memory mapped and occupies only 16 bytes of memory space. The board base address is switch selectable and can be placed anywhere in the first megabyte of host memory space.

The AVT-921 comes with a User’s Manual and telephone technical support. A 10 foot OBD-II compatible cable assembly is also available.

The AVT-921 Dual J1850 Interface (VPW and PWM) is available for immediate delivery. Questions and requests for additional information on the AVT-921 or any of our other automotive network products can be directed to Michael Riley.


Site Map