Allen-Bradley devicenet modules in logix5000 control systems Manual Do Utilizador
Publication DNET-UM004A-EN-P - March 2004
Control a Device 7-11
Determine If a Device Has
Failed
Failed
If a DeviceNet device stops communicating (device failure, cable
break, etc.), the tag for the device stays at its last value. To make sure
that your input data is valid, we recommend that you buffer the input
data and examine the device failure register.
break, etc.), the tag for the device stays at its last value. To make sure
that your input data is valid, we recommend that you buffer the input
data and examine the device failure register.
Indication that a device has failed.
• There is 1 bit for each address on the DeviceNet network.
• If a bit = 1, then the device at that address has failed.
Addresses 0 to 7
Address 0
Address 1
Address 1
Addresses 8 to 15
On every scan of the controller, execute logic similar to the following:
If PhotoEye_RawData = 1 and PhotoEye_Failed = 0 then
PhoteEye = 1
Otherwise PhoteEye = 0
Use the PhotoEye tag in the rest of your logic (not PhotoEye_RawData).
input data from
device
failure bit for
device
data for your logic