V50 L5-2.4L VIN 39 B5244S7 (2005)
CAN Network
CAN network
General
CAN (control area network) is a standardized system for multiplex-communication. Multiplex communication means that several control modules can
use the same cables for communication without traffic from one control module interfering with traffic from another.
Volvo has developed a new standard for multiplex communication - VOLCANO. VOLCANO is a development of CAN and uses real time operation and
prioritization. The description of prioritization is based on VOLCANO but is designated CAN.
The control area network (CAN) standard specifies:
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That two cables are to be used (CAN H and CAN L)
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What voltage levels must be used
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What a message should look like
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How transmission errors should be handled.
Cables, CAN H and CAN L
The CAN H and CAN L cables must not be confused with HS CAN and LS CAN which are speeds on the control area network. CAN H and CAN L are
a way of distributing signals within the multiplex communication network.
Communication occurs through two cables. These two cables are paired together.
The voltage levels for communication occur using differential voltage levels.
The reason for communicating using paired cables and differential voltage levels is that the network becomes less sensitive to interference.
The same message is transferred simultaneously by both cables, but different voltage levels are used.
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Binary 1 = 2.5 V on both CAN H and CAN L.
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Binary 0 = 4 V on CAN H and 1 V on CAN L.
When measuring between CAN L and ground, the average voltage level during normal use is about 1.8-2.2 V.
When measuring between CAN H and ground, the average voltage level during normal use is about 2.8-3.2 V.
The difference in voltages is due to vehicle configuration and equipment level. Thus, voltages may differ between vehicles of the same model.
Control area network (CAN) message
