1. Scope--The CSC Bus components defined herein were developed to provide simple, yet reliable, communication between a host master module and its sensors and actuators. The scheme chosen provides the ability to communicate in both polling mode and direct addressing modes.

1.1 Background--Vehicle applications for multiplexing can be broken into three broad classifications:

a. Class A - Sensor and Control Multiplexing b. Class B - Data Communications c. Class C - High Speed Real Time Control

Sensor and Control Multiplexing is the more classical form. An example of this kind would be fluid level sensors, door/hatch switches, and control of the vehicle headlamps, tail lamps, stop lamps, horn, wipers, etc., through a multiplex wiring network. Normally, Control Multiplexing affects the base vehicle wiring system, which directly affects the base cost. On the other hand, Data Communications multiplexing (Class B) interconnects intelligent modules such as the engine controller, body computer, vehicle instrument cluster, and other electronic modules. It normally does not affect the base vehicle wiring but provides an intermodule data communications link for distributed processing and, if properly partitioned, will reduce costs on all but the base vehicle. Finally, there is a class of medium to very fast real time control modules such as the engine controller, automatic transmission, and antiskid controller.

Class B Multiplexing is a very useful technique for reducing the problems encountered by the automotive electronic system engineer. However, in many situations Class B multiplexing leads to a less than optimum system. This Class B Network can be an effective enabler to vehicle integration but it does not solve the sensor and actuator connection problem. After a careful study of the current Class B Network, it was obvious that a different system needed to be developed. Statistically speaking, it was determined that there are approximately seven sensors to every actuator in a potential Class A Multiplex Network. A form of multiplexing which would permit smaller module connectors and reduce the number of wires crowding through the congested areas without introducing more modules is highly desirable. The Chrysler Sensor and Control (CSC) Bus is a style of multiplexing which meets these objectives.

Another problem presented to the System Designer consists of implementing different levels of option content. Base vehicles receive limited electronic feature content, medium vehicles receive some optional electronics, and premium vehicles contain an extensive amount of electronic features. CSC multiplexing has the ability to solve this variable content uncertainty as well as the wiring congestion problem.

1.2 CSC A Potential Class A Multiplex Network--The proposed solution defined herein integrates a multiplexer with a Hall Effect Sensing Element and replace the reed switch used in current sensors. When standard switches are given multiplexing capability they are really sensors. They no longer 'switch' as they do today. Instead they 'sense' some parameter and report back the status including sensor diagnostics. The CSC Bus allows for increased feature content in existing modules by connecting additional sensors. More exotic sensors are also practical using multiple CSC sensors.

Perhaps the biggest factor and criteria of judgment as to whether a Class A multiplexing network will be successful or not is cost. The CSC sensors have been designed to include the multiplex circuit integrated with the Hall Effect Device in the same TO92 size package. The multiplexer portion is very small and requires approximately 300 logic gates.