Omron CJ1W-DRM21 Operation Manual page 285

Event name Bus Off Detected
Meaning A Bus Off error occurred (i.e., communications stopped because there were too many communications errors).
Source PLC Function Module
Error attributes Level
Effects User program
System-defined Variable
variables
None
Cause and Assumed cause
correction
The master and slave have different
baud rates.
Communications cable lengths (trunk
line and branch lines) are unsuitable.
A communications cable is discon-
nected or loose.
The terminating resistance is some-
where other than the ends of the trunk
line.
Noise
Attached None
information
Precautions/ None
Remarks
CJ-series DeviceNet Units Operation Manual for NJ-series CPU Unit(W497)
Source details
Minor fault Recovery
Continues. Operation
Data type
---
Correction
Correct the settings so that the mas-
ter and slaves use the same baud
rate.
Refer to the communications specifi-
cations and adjust all of the communi-
cations cables to suitable lengths.
Connect the communications cable
securely. If the communications cable
is broken, replace it.
Connect terminating resistance only
to the ends of the trunk line.
Implement noise countermeasures.
9 Troubleshooting and Maintenance
Event code 84740000 hex
CJ-series Unit Detection
timing
Cycle the power Log category
supply or reset
the Controller.
The DeviceNet Unit is offline. Communications will not
operate. Error responses are returned to all communica-
tions requests. Data refreshing with the CPU Unit contin-
ues.
Name
---
Prevention
Set the master and slaves to the
same baud rate.
Refer to the communications specifi-
cations and adjust all of the communi-
cations cables to suitable lengths.
Connect the communications cable
securely. Check the communications
cable to see if it is operating properly.
Connect terminating resistance only
to the ends of the trunk line.
Implement noise countermeasures.
When the I/O
connection is
established or
DeviceNet com-
munications are
performed
System
9
9-55