Omron cx programmer DIFU and DIFD, one-shot instruction

kokomel

Member
Join Date
Jun 2011
Location
australia
Posts
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The code of Emergency switch is following, when you press the switch the machine stop.
In ControlFunctions :

DIFU and DIFD is same variable : ipb_emergency_stop_sw, BOOL data type

on Set/input rung of a KEEP instruction(variable :gpb_emergency_stop,BOOL)

---------DIFD------------------------gpb_emergency_stop

on Reset rung

---------DIFU------------------------gpb_emergency_stop

In Process :

DIFD now is gpb_emergency_stop

on Set/input rung of Keep instruction(variable: sta_power_on,BOOL)

---------DIFD------------------------sta_power_on

can anyone explain DIFU and DIFD in here, anything to do with scan cycle ? why DIFD is placed on Set rung of sta_power_on Keep instruction not on Reset rung ?
 
Of course the actual cutoff of power should take place outside the PLC. But a STOP wired function should be wired such that it takes place when an input turns OFF. This is to take into account a possibility that the wiring from the STOP device becomes disconnected.

Therefore the turn off (DIFD) actuates the 'emergency stop' function (whether this happens because the stop device is indeed actuated or the wiring is somehow disconnected.)

Only if the input turns on, implying a proper release of a properly wired actuating device, is the 'emergency stop' removed.
 
Thank for answering, but you are a bit off the track, my theory is Set rung is supposed to turns on bit sta_power_on and Reset rung turns off the bit or shows what is the next state. Why DIFD is placed on Set rung why it should have been on Reset rung. If possible can you talk more about scan cycle, i mean the one-cycle of one-shot instruction, i dont understand it here, I appreciate.
 
Thank for answering, but you are a bit off the track, my theory is Set rung is supposed to turns on bit sta_power_on and Reset rung turns off the bit or shows what is the next state. Why DIFD is placed on Set-rung,it should have been on Reset-rung. If possible can you talk more about scan cycle, i mean the one-cycle of one-shot instruction, i dont understand it here, I appreciate.
 

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