Description:
With PCS 7 V5 and higher the "CH_AI" block is used as an analog input driver for the new PCS 7 driver concept.
This block offers the option of simulating the input value.
For this there is an input SIM_ON, with which the simulation is activated. The simulation value is entered at the input SIM_V or done by an interconnection.
If simulation is activated by setting the input "SIM_ON" (SIM_ON = TRUE), then this value is output at output "V".

Problem:
This only works if a valid "MODE" value is at the "MODE" input. This is always the case when the driver block is interconnected with the symbolic measuring point designation (input "VALUE"), the appropriate hardware is configured and the driver wizard has then interconnected the "MODE".
If you insert a new CH_AI block in the CFC chart, then simulation is not possible, because the value 16#0000 0000 is not a valid "MODE".
As can be seen in Figure 1, the value at input "SIM_V" is not output at output "V" despite activated simulation.



This behavior is very unfavorable, for example, when you want to test parts of the user program, but the hardware has not yet been configured. There are two possible remedies:

Either you change the interconnection from the driver block output "V" to another block, with which you can make a value available (e.g. OP_A_LIM). This however has the disadvantage that you later have to "interconnect back again. The risk here is that something will be incorrectly connected or even forgotten altogether.

The simpler method is to enter a valid "MODE" value manually at the input, for example 16#0000 0109. An example is shown in the figure.



Keywords:
Measured value simulation