Unity Pro DFB inputs default value

HaroonKhan

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Join Date
Jul 2009
Location
Brisbane
Posts
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I am trying to set up default values for Unity input pins, but can't find any way I can do so. Currently, the pin retains the last value that was enterred.

In RSLogix I can write to the input pins, so I can set a default value at the end of an add-on-instruction, but since I can't write to a Unity DFB input, the last value remains.

Any ideas?
 
what about creating variables and put them on the pins. then write values to variables......there should be an easier way i think
 
in a operator block in ladder or a move instruction in fb, use the name of the dfb and then the pin name.
example
want to write to the dfb motor and the pin start

| |--------------------------------motor.start:=1


can do this with any type of bin....i think
 
Thanks for your response Chud, but I was more after a feature in the DFB which allows me to set a default value so that if someone used the DFB and didn't connect the pin, it would use a default value.
 
but then what geoffc suggested is exactly what you want. if nothing is written on the pin and the initial value is set to what you enter at the value field, then thats the default value. it cannot change unless written to
 
Thanks for the tip Lare, but already tried that. The problem is that Unity holds last value for a DFB input (I beleive Rockwell does the same).

So if you connected 5 to the variable and then disconnected it, the input would remain 5, not change to 0.
 
compare and move block works if you put them inside your own derived function blocks, input variable have to be declared to in/out variable, so that you can write to it inside dfb-block.

Lare
 
How do you disconnect a dfb input under program control?
Surely you insert a dfb connect required inputs and then those not connected will be at the initial value
 
The initial value is overwritten as soon as the user writes a new value to that input. This new value stays active even if someone disconnects the pin as it holds the last value.

I have spoken to Schneider regarding my problem and so far they have no answer.
 

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