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4. Troubleshooting (DeviceNet)
4.1.3.4 Broken Unit Examination (Dividing Network Examination)
When you cannot quickly find the trouble point due to a broken unit, connection failure
including loose connector, or cable partial disconnection, divide the network to find the
trouble point. Verify how error occurrence conditions change while taking the following
countermeasures.
How to Examine
Divide the network to find which node is the cause of the problem.
Verify that a master can establish communications with the slaves even though one slave is
separated from the network.
After finding the problem node, check the cables connected to it and replace the unit.
How to Divide
To divide the network, follow either procedure described below depending on the cable
layout.
(1) Separating each block from the network
Divide the network by block and check each block.
1. Ensure that the master has no problem by connecting it to its slaves one by one.
(MS/NS: green light ON)
2. Divide the network in the middle of it and check for the communication condition.
(MS/NS: green light ON)
Normal: The trouble point is on the other half of the network.
Error: The trouble point is on the current half of the network.
(Continue dividing the half of the network further to distinguish error part from
normal part.)
3. Check for communication on the block to specify the trouble point.
PLC
Slave
Branch Tap
Communications
Power Supply
Terminating Resistor
Branch Tap
Slave
Slave
Terminating
Resistor
Maste
r
Slave
Connect the terminating resistor to the branch
taps one by one to specify which device is the
limit of the normal communications.
104 Fieldbus I/O Rev.6