S7- CPU 314 analoge force

[ahmed megahed]

Hi gentlemen

Is it possible to force an analoge value in these CPU before 400
what i notice is i cannot write PIW128 in force table to force it ?

and also i tried to force IW128 instead of PIW128 is it the same or no ?

 

[MikeDawkins]

Try forcing the bit pattern for the value you want in I128.0 through I129.7. Remember the LSB is in I129.

 

[JesperMP]

Analog inputs are normally placed in the periphery inputs (PIW instead of IW). So you cant just force these.

You probably have a scaling function, to convert the raw input to engineering values.
Add a simulate-bit as a condition (N.C. contact) before the scaling function. When you set the simulate-bit, the scaling isnt done. You can then manipulate the scaled value without it being updated by the scaling function.

 

[ahmed megahed]

Hi JesperMP
Thanks for your idea, it is OK.
But i need a clear answer is it possible to force analoge PIW by direct way like S7-400 or no ?
thanks

 

[KalleOlsen]

Hi JesperMP
Thanks for your idea, it is OK.
But i need a clear answer is it possible to force analoge PIW by direct way like S7-400 or no ?
thanks

It is not possible to force a PIW or to write to a PIW.

When the CPU reads a PIW, the value is accessed instantly from the input card via the backplane bus.

Dependant of the cpu type you can expand the process image area and thus put your analog(?) values in the IW area. The IW can then be overwritten with a T IW command.

Kalle