ADVANCED VEHICLE TECHNOLOGIES, Inc.
Data sheet 059, June 1997

AVT-716 - Triple Interface (J1850 VPW, PWM and ISO 9141)

Vehicle Networks
As the use of electronics in automobiles increases so do the requirements for communications among the various processors and modules as well as engineering test and diagnostic equipment. Federal law requires that vehicles support any of three communications standards at the diagnostic connector (known as OBD-II). The three standards are: J1850 VPW, J1850 PWM, and ISO 9141-2. Complicating the use of these in-vehicle networks is that none are compatible with the others.

The AVT Solution
The AVT-716 Triple Interface is a single unit solution to communicating with these three network standards. It is an easy to use interface that solves the problem of connecting to and communicating with an OBD-II equipped vehicle or network module. The AVT-716 Triple Interface supports all three of the standards (J1850 VPW, PWM, and ISO 9141-2). The user selects the desired mode of operation via a software command (simultaneous operations are not permitted). Operational mode changes may be accomplished at will and without restrictions.

The Triple Interface is available housed in an enclosure or as an OEM module. Also offered is Controller software and an OBD-II compatible cable (for direct vehicle connection).

The AVT-716 Controller Software
• The AVT-716 Controller software can operate in command mode which permits operator introduction of network messages onto the selected network. This mode permits the testing of node interactions to specific message sequences and other user defined test scenarios. Commands can be entered individually or downloaded via a batch file.

• A network monitor mode permits the capture and display of bus traffic. Options to timetag and log the data to a file ensures an historical record of network activity for later analysis. The disk logging function is limited only by the amount of available disk space.

• The Controller software was designed to support engineering uses (testing, data acquisition, etc.). One Controller feature is the ‘Auto-Respond’ function. The operator specifies a ‘match string’ and a response file. Every received network message is compared to the match string. If a match is found, the next line of the response file is immediately transmitted.

• The AVT-716 Controller runs on PC-AT machines under MS-Windows 3.1x. A 66 MHz 80486 with 8 MB of memory and at least 2 MB of disk space is the minimum recommended host.

The AVT-716 Hardware
The AVT-716 Hardware Interface unit provides an isolated electrical interface between a host computer and the three networks (J1850 VPW, PWM, and ISO 9141). It performs the necessary protocol conversions and all required communication translations allowing a user with a PC to communicate with a vehicle or module.

SAE standard J1850 specifies a Variable Pulse Width (VPW) version with a bit rate of 10.4 kbits/sec. and a Pulse Width Modulation (PWM) version with a bit rate of 41.6 kbits/sec. ISO standard 9141-2 specifies a data rate of 10.4 kbits/sec. The AVT-716 was designed to communicate with all three of these protocols. Additionally, the AVT-716 supports transmit and receive operations in VPW mode at 4 times the normal rate. (Operations at 4X speed in VPW mode may be required for some GM Class 2 modes.)

The architecture of the AVT-716 is compliant with the Ford Motor Standard Corporate Protocol (SCP).

The AVT-716 was designed to be connected directly to the subject vehicle and the host computer. Power for the AVT-716 is provided by the vehicle through the OBD-II connector. The AVT-716 communicates with the host computer via either an RS-232 or RS-422 serial interface. The interface and baud rate (four baud rates are available) are selected by configuring four jumpers. Optical isolation is used on the AVT-716 to electrically isolate the host computer from the subject vehicle at the serial interface.

The AVT-716 Interface consists of two printed circuit boards (mated together, back to back). Board #1 consists of the microcontroller, ROM, RAM, serial controller, operation indicators, and real time clock. Board #2 functions include the optically isolated serial interface to the host computer, the three network interfaces, and the regulated power supply.

The AVT-716 is available housed in a rugged polycarbonate enclosure or as an OEM module (circuit boards only). The Controller software and an OBD-II compatible cable (permitting direct vehicle connection) are also available.

All AVT equipment is warranted for one year from date of purchase. Free software and firmware upgrades are available for one year from date of purchase. Prompt telephone technical support is always available.

Specifications

Size: 4.0 x 5.6 x 1.4 in. (OEM module), 5.2 x 6.8 x 2.3 in. (enclosure).
Weight: 18 ounces (7 oz. OEM only).
Voltage: +8 to +25 VDC (from vehicle).
Power: 2 watts (nominal).
Host interface: RS-232 or RS-422 (jumper selectable).
Host baud rate: 9.6, 19.2, 38.4, 57.6 kbaud (jumper selectable).
Connectors: DE-9S and DA-15P.
Microcontroller: MC68332 @ 16 MHz (Motorola).

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