Information Bus: Description and Operation

CCD BUS
The CCD (Chrysler Collision Detection multiplex system) bus is the means of communicating between the Airbag Control Module (ACM) and the DRB III (R) about the operation of airbag system components and circuits.

The Chrysler Collision Detection multiplex system (CCD bus) consists of a twisted pair of wires. These wires run from the airbag control module (ACM) to the data link connector and the DRB III (R). They receive and deliver coded information between the ACM and the DRB III (R).

The two wires (D1 and D2) of the twisted pair that make up the CCD multiplex system are called "bus+" (bus plus) and "bus-" (bus minus) respectively. Each wire has a measurable voltage level of roughly 2.5 volts, which is supplied by the DRB III (R). In order to maintain the 2.5 volts on each line and provide a means of transportation for the coded messages, there is a "voltage divider network." This network, contained in the DRB III (R), supplies bias and termination. Bias is the part of the voltage divider network that places both bus+ and bus- at 2.5 volts. Termination in the circuitry is required to complete the voltage divider network and also to provide some electromagnetic protection for the bus.