Information Bus: Description and Operation

Communications Network

Multiplexing is a method of sending 2 or more signals simultaneously over a single circuit. Multiplexing allows 2 or more electronic modules (nodes) to communicate simultaneously over a twisted-wire pair [data (+) and data (-)] network. The information or messages that can be communicated on these wires consists of commands, status or data. The advantage of using multiplexing is to reduce the weight of the vehicle by reducing the number of redundant components and electrical wiring.

The vehicle has 2 module communication networks connected to the Data Link Connector (DLC) and communicate with the scan tool. The communication networks are:

- High Speed Controller Area Network (HS-CAN)

- Medium Speed Controller Area Network (MS-CAN)

The Infotainment Controller Area Network (I-CAN) is connected to the DLC (Data Link Connector), but the I-CAN (Infotainment Controller Area Network) modules communicate with the scan tool over the MS-CAN (Medium Speed Controller Area Network). The Front Control/Display Interface Module (FCDIM) is used as a gateway module for the messages to transfer between the scan tool and the modules on the I-CAN (Infotainment Controller Area Network).

Network Topology










Network Termination

The CAN (Controller Area Network) uses a network termination circuit to improve communication reliability. The network termination of the CAN (Controller Area Network) bus occurs inside the termination modules by termination resistors. Termination modules are located at either end of the bus network. As network messages are broadcast in the form of voltage signals, the network voltage signals are stabilized by the termination resistors. Each termination module has a 120 ohm resistor across the positive and negative bus connection in the termination module. With 2 termination modules on each network, and the 120 ohm resistors located in a parallel circuit configuration, the total network impedance, or total resistance is 60 ohms.

Network termination improves bus message reliability by stabilizing bus voltage, and eliminating electrical interference.

Gateway Module

The IPC (Instrument Panel Cluster) is the gateway module, translating HS-CAN (High Speed Controller Area Network) to MS-CAN (Medium Speed Controller Area Network) and vice versa. The FCDIM (Front Control/Display Interface Module) is the gateway module, translating MS-CAN (Medium Speed Controller Area Network) to I-CAN (Infotainment Controller Area Network) and vice versa, allowing a message to be distributed throughout the three networks. The IPC (Instrument Panel Cluster) and the FCDIM (Front Control/Display Interface Module) are the only modules on this vehicle that have this ability.