Control Logix ENBT module time out speed (fault)

[andyhoover05]

Hello,

I am testing a communication drop out. I was wondering if anyone knows how quickly an ENBT module faults after communications is lost. Is it instantaneous (as soon as the module loses comms, it triggers the fault bit) or does it wait a certain amount of time to trip the fault bit?

The two modules are as follows: 1756-ENBT /A Rev. 1.61
and..............................1756-enbt /A Rev. 2.4

Thanks in advance.

 

[Ken Roach]

If presume that you're talking about an I/O connection using the EtherNet/IP protocol.

EtherNet/IP uses a mechanism similar to DeviceNet for I/O connection timeouts; the timeout value is four times the expected packet rate (EPR, a DeviceNet term) or the RPI (Requested Packet Interval, a ControlNet and EtherNet/IP term).

If you set up a Rack Optimized connection, for example, to the remote chassis with an RPI value of 20 milliseconds, the 1756-ENBT will declare a connection error if 80 milliseconds pass without a data packet for that I/O connection.

How are you determining a connection fault ? There is no "fault bit" as such, rather there is a Connection Status value available using the Get System Variable (GSV) instruction.