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SCL. Declare input as const ?

Created by: Gustaf_ at: 8/24/2012 10:37 AM (5 Replies)

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8/24/2012 10:37 AM	Rate (0)
Gustaf_ Posts: 50 Rating: (0)	Hello, Is it possible to declare an input as constant to a SCL FB ? I do not want a variable that can change at runtime ... Gustaf
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8/24/2012 11:03 AM	Rate (1)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/23/2023 Posts: 1523 Rating: (518)	I don't believe that this is possible. I can offer some alternative suggestions. 1) Use a DB. Put your constant data in the DB and read it from that. 2) Have a normal input, but set the S7_visible attribute to false. This way the input will not show on the block. In both these cases, the value still modifiable at runtime, but not without the user making some effort to do so. They certainly cannnot do it by "accident".
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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8/24/2012 11:06 AM	Rate (0)
Gustaf_ Posts: 50 Rating: (0)	Thanks!
Gustaf_ Posts: 50 Rating: (0)
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2/23/2016 2:11 PM	Rate (0)
Cimant Experienced Member Joined: 3/19/2012 Last visit: 3/23/2023 Posts: 40 Rating: (2)	You can declare a constant in SCL by declaring CONST Max_Number:=16; END_CONST VAR_INPUT your_Variable : INT ; END_VAR you can't define an INPUT as a constant. But you can enter a value so when you compile your code, the SCL automatically fills that variable with that number. VAR_INPUT your_Variable : INT := 16; END_VAR But this variable can be overwritten...

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2/25/2016 3:42 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 3/15/2023 Posts: 1410 Rating: (146)	If you want a constant then you have a declartion for constant, it can't be input variable and constant at the same time, because if you can change it (input variable) then it is no longer a constant.

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2/26/2016 1:34 PM	Rate (0)
Duris_I Diamond Member Joined: 4/28/2015 Last visit: 3/24/2023 Posts: 9164 Rating: (723)	Maybe Gustaf meaned like in OOP, there some other things can be made, but this is really different world
	With best regards... Ivan Duris VId: OMICO
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