Dear expert,

Yesterday i faced a problem that if communication fails from HMI and PLC which communicate on profinet,button defined on screen got stuck and due to that machine transfer trolley start going forward/reverse during failure of communication.

During communication failure ???? comes on screen and which button is pressed before communication failure remain active and due to this command comes from HMI to PLC my sinamic drive get on and stop only applying EMG s/w which is done on hard wiring in PLC.

I solved this problem by replacing profinet cable but it is strange to understand how PLC send command to turn on drive during communication failure?????

Regards,

Pankaj Tiwari

May we assume that you are using the "SetWhileKeyPressed" action?


Figure 1. Implementing a press-and-hold functionality

Understand that this function is in actual fact two actions:
1) set bit when button pressed down
2) reset bit when button released

A break in communication means that action (2) is not processed. The PLC is only aware of action (1) which means the bit remains active. 

An old school solution would be to never use press-and-hold type functionality from a software button (HMI). The HMI activates a function but a hardware button executes the function.

The alternative is to use the co-ordination area pointer to detect when the communication is not active. Using the "life bit" would mean that the realization that there is a break in communications may take 2s or so.


Figure 2. "Coordination" area pointer as documented in software help.

Are these the 'droids hints you were looking for?

pankaj_054

thank u so much for your explanation,i understood your point.

Good to have your feedback. Please confirm: Was my guessing correct and does it close this topic?

As topic creator you can mark the post as solved. Use the ACTIONS button.