Controller Area Network Data Bus
The communication protocol being used for the CAN-C data bus is a non-proprietary, open standard adopted from the Bosch CAN Specification 2.0b. The CAN-C is the faster of the two primary buses in the hybrid bus system providing near real-time communication (500 Kbps).
The CAN-C bus nodes are connected in parallel to the two-wire bus using a twisted pair, where the wires are wrapped around each other to provide shielding from unwanted electromagnetic induction, thus preventing interference with the relatively low voltage signals being carried through them. The twisted pairs have between 33 and 50 twists per meter. While the CAN bus is operating (active), one of the bus wires will carry a higher voltage and is referred to as the CAN High or CAN bus (+) wire, while the other bus wire will carry a lower voltage and is referred to as the CAN Low or CAN bus (-) wire. Refer to the following CAN-C bus voltage Chart.
| CAN-C Bus Voltages (Normal Operation) | ||||||||
|---|---|---|---|---|---|---|---|---|
| Bus Circuit | Sleep | Recessive (Bus Idle) | Dominant (Bus Active) | CAN-L Short to Ground | CAN-H Short to Ground | CAN-L Short to Battery | CAN-H Short to Battery | CAN-H Short to CAN-L |
| CAN-L (-) | 0 V | 2.4 - 2.5 V | 1.3 - 2.3 V | 0 V | 0.3 - 0.5V | Battery Voltage | Battery Voltage Less 0.75 V | 2.45 V |
| CAN-H (+) | 0 V | 2.4 - 2.5 V | 2.6 - 3.5 V | 0.02 V | 0 V | Battery Voltage Less 0.75 V | Battery Voltage | 2.45 V |
| Notes | ||||||||
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All measurements taken between node ground and CAN terminal with a standard DVOM. |
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DVOM will display average network voltage. |
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Total resistance of CAN-C network can also be measured (60 ohms). |
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The CAN-C bus network is awake only when the ignition switch is in the On or Start positions. However, an individual node on the CAN bus may still be awake with the ignition switch in the Accessory or Unlock positions. This is because the integrated circuitry of an individual node may be capable of processing certain sensor inputs and outputs without the need to utilize network resources.