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can_higher_layer_protocols:duplicate_mac_id [2018/08/21 23:08] (current)
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 +====== DeviceNet 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 =====
 +  * Transmit Dup MAC request message
 +  * Wait 1 second (listening for replies - see 1 below)
 +  * Transmit Dup MAC request message
 +  * Wait 1 second (listening for replies - see !1 below)
 +  * Transition to Online State
 +
 +!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:
 +  * manual Intervention (power cycle, device reset or other manual intervention)
 +  * 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 connection 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&#​039;​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 specification.
 +
 +Nick Jones, Oct 15. 2002
 +[[http://​odva.or.kr/​devicenet_resources/​DrDeviceNet/​pc.htm | Dr. Devicenet]]
 +
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