DuplicateMacId


Duplicate MAC ID protocol summary:

(in the following explanation "Dup MAC Request/Response" means a Duplicate MAC ID Request/Response message at the same MAC ID as the node being described)

Power-up

!1 - During two 1-second timeout periods above 1a) If a Dup MAC request or response is received transition to the

 Communication Fault state

!2 - While in the Online state 2a) If a Dup MAC Request message is received, send Dup MAC Response 2b) If a Dup MAC Response message is received, transition to the

 Communication  Fault state.
(this situation seems unlikely, but can occur if two network segments are powered up and then connected together)

There are two ways to leave the Communication Fault state:

1) Manual Intervention (power cycle, device reset or other manual intervention) 2) MAC ID is changed (possibly to the same value) via the offline connection set which causes the device to re-start the media access state machine. This option is only available if the device supports the offline conenction set.

Generally speaking, if a duplicate MAC ID fault occurs, you must identify the node(s) with the incorrect MAC ID, make corrections, and cycle power on the network, or remove & reconnect specific devices, to bring the network up.

If the affected devices support the offline connection set it is possible to change the MAC ID's and reset faulted devices from a configuration tool without cycling network power or disconnecting devices.

This email is intended to be a general explanation, for complete, 100% accurate information please refer to Volume I, Chapter 4-7.3 and Chapter 6 in the DeviceNet specficiation.

Nick Jones, Oct 15. 2002


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