Communication - Description

DESCRIPTION

The primary on-board communication network between microprocessor-based electronic control modules in this vehicle is the Chrysler Programmable Communication Interface (PCI) data bus system in combination with the CAN-C data bus, which forms a hybrid bus system. A data bus network minimizes redundant wiring connections; and, at the same time, reduces wire harness complexity, sensor current loads and controller hardware by allowing each sensing device to be connected to only one module (also referred to as a node). Each node reads, then broadcasts its sensor data over the bus for use by all other nodes requiring that data. Each node ignores the messages on the bus that it cannot use.

The CAN bus is a two-wire multiplex system, while the PCI bus is a single-wire multiplex system. Multiplexing is any system that enables the transmission of multiple messages over a single channel or circuit. The CAN bus is used for communication between the Powertrain Control Module (PCM) and the Occupant Classification Module (OCM), while all of the remaining body and interior nodes use the PCI bus.

The CAN-C data bus is the faster of the two systems providing near real-time communication (500 Kbps), while the PCI bus communicates at a much slower 10.4 Kbps. The CAN-C is used typically for communications between more critical nodes, while the slower PCI system is used for communications between less critical nodes.

The added speed of the CAN-C data bus is many times faster than previous data bus systems. This added speed facilitates the addition of more electronic control modules or nodes and the incorporation of many new electrical and electronic features in the vehicle.

The PCI bus also provides diagnostic access between a diagnostic scan tool connected to the industry-standard 16-way Data Link Connector (DLC), located below the driver side instrument panel and all nodes on either bus through a Central GateWay (CGW) or hub module. The CGW module is secured to the floor under the driver side front seat in the passenger compartment. This gateway physically and electrically isolates the CAN and PCI buses from each other and coordinates the bi-directional transfer of messages between them.