The J1850 Automotive Multiplexing System is opening up new opportunities for automotive designers. Multiplexing not only reduces wiring, weight and cost; but is also adding features by sharing information among modules. For example a door module could communicate that the car is being unlocked and who is unlocking it. The body controller can use this information and tell smart seats and mirrors to adjust themselves to that driver's preferences; tell the radio to turn to a particular station and start the engine. The number of modules that are being multiplexed are increasing in both number and function. Everything from sophisticated engine controllers to simple actuator/sensor nodes are being multiplexed.The challenge with Multiplexing a large number of modules is how to make an integrated circuit that fits all their diverse needs. A complex module, like an engine controller, requires the integrated circuit to be sophisticated enough to handle all the message buffering and filtering functions. Whereas a very cost sensitive, low end module does not require the same performance. How does an IC meet the conflicting needs of an increasing number of modules?Harris Semiconductor found an answer by taking a building block approach. Harris implemented the J1850 analog and digital functions into separate integrated circuits. Doing this not only developed a flexible solution but one optimized to a degree not possible using a single integrated circuit. This article will explain how the three Harris J1850 integrated circuits (HIP7010, HIP7020 and the HIP7030) make up a flexible and cost effective solution for the J1850 Variable Pulse Width Modulation (VPW) Standard.