What are the restrictions for CANpen cable lengths connected to CANTAP (VW3CANTAP2) ?

CANopen architecture is based on "bus" topology. Any branches derived from the bus are called stubs or stub lines (sometimes just branches). These branches create reflections when the signal goes to and from a device at the end of the branch. Avoid branches as much as possible. Tolerance to a certain length in branches depends on CANopen speed.

• There is a limit of max connection length for one branch.
• There is a limit for the total length of branches per one CANopen tap (sum of branches lengths connected to one tap)
• There is a certain min distance L between two CANopen taps, depending on the length of the branches. L > 60% of the sum of all branches in a TAP.
• The following table shows the limits of CANopen length per branch, total length per tap and min distance between taps, and total sum (sum of all branches in the whole CANopen network)

Example:
bus speed is 500kb/s
Max branch length can be 5m, (total max 10m per one TAP)

Let's say that there are 2 taps: Tap1 and Tap2
Let's say than distances between Nodes and Taps are:
Node1-Tap1 = 1m
Node2-Tap1=3m
Node3-Tap2=0.3m
Node4-Tap2=1m
min TAP distance between Tap1 and Tap2 is then L > 60% * max (sum per tap1 , sum per tap2) = 0.6 * max (1m+3m , 0.3m +1m) = 0.6 * 4m = 2.4m
Distance between Tap1 and Tap2 must be at least 2.4m

Publié pour: Schneider Electric Belgium