Slave: Data Link Error

	MS	NS
Master LED Condition	Light OFF	Red Light Blinking
Absent Slave LED Condition (Data link error)	Light OFF	Red Light ON

Process Flowchart

* See also:

Symbol	See also:
1	Disconnected Terminating Resistors, Cable Disconnection, Disconnected Connector, and Disconnected Signal Wire
2	Loose Connector and Signal Wire
3	Noise Intrusion

Causes of Error

Possible Cause	Examination Method	Countermeasure
Disconnected terminating resistors Cable disconnection Disconnected connector Disconnected signal wire	Check that terminating resistors are connected to both ends of the network. Measure resistance between signal wires with device power supply OFF. → Normal: 100 to 120 Ω Measuring point: Connection of the problem unit See also: Disconnected Terminating Resistors, Cable Disconnection, Disconnected Connector, and Disconnected Signal Wire	Fix the problem. How to find the trouble point: Remove the terminating resistor on one end of the network. The trouble point is where resistance changes from 220 Ω.
Loose connector Loose signal wire	Check for the connection of connectors and signal wires. → The connectors and signal wires should be firmly connected. Checkpoint: Checkpoint: all stations and all branch taps See also: Loose Connector and Signal Wire	Connect the connectors and signal wires again.
Noise (external cause)	Check the noise intrusion via the following paths (1) to (3). Noise via shield Induced noise via communication cable Device power supply → See also: Noise Intrusion	Take countermeasures against noise.
Broken unit	Replace the trouble unit with a new one. → Verify whether the problem is fixed.	Replace the unit with a new one.
No cause is identified.	Identify the trouble point by dividing the network. → See also: Broken Unit Examination (Dividing Network Examination)	-