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8.3.4 Collisions
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Error source
The number of hubs in the EPL network is notmay violate the path delay variability
specification of IEEE 802.3. Because standard Ethernet controllers according to
IEEE 802.3 are used, collisions can be detected only in some cases.
Ethernet POWERLINK doesn't depend on the discovery of collisions.
In
NMT_CS_READY_TO_OPERATE and NMT_CS_OPERATIONAL, no collisions should
occur due to the EPL cycle design. If a node doesn't follow these requirements,
then the determinism and the high precision synchronisation cannot be
guaranteed anymore. Nevertheless collisions can occur in case of configuration
failures or defect nodes.
●
Error recognition
If the Ethernet controller discovers a collision in the EPL network, the standard
Ethernet procedure for collisions is started.
●
Error handling
If a Collision error is detected, it is logged as Error code in the StatusResponse
frame and transmitted then to the MN. Error reaction is triggered by the threshold
counter mechnism in Object 1C0Ah: DLL_CNCollision_REC on page 151. If the
threshold counter violates the threshold, the CN NMT state machine is handle this
error source as "Internal Communication Error" (NMT_GT6) and changes the
measuring system state to NMT_GS_RESET_APPLICATION.
●
Error signaling
With the internal error function mechanism the error is registered into the "Static
Error Bit Field". The Static Error Bit Field is part of the StatusResponse frame.
Format:
Byte Offset
3-8
Table 17: Static Error Bit Field, fragment of the StatusResponse frame
Printed in the Federal Republic of Germany
06/26/2017
NMT_CS_PRE_OPERATIONAL_1,
Description
1 Content of Object 1001h: ERR_ErrorRegister_U8, 0x01
2 reserved
Error Code = 0x8163
TR - ECE - BA - DGB - 0071 - 05
NMT_CS_PRE_OPERATIONAL_2,
 TR-Electronic GmbH 2008, All Rights Reserved
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