Thermostat with setpoint retention exposed via Modbus

Hi guys,

I can't figure out how I can create thermostat with retentive setpoint, hysteresis and setpoint value controlled via Modbus.

So far I have this:

It seem to work, however I have to configure two parameters via Modbus, there is no input validation at all and this is not acceptable.

I can't figure out how to dynamically assign a value to the Off parameter based on the current value of On (or any other block that accepts data from modbus, has retention and allows to control thermostat somehow). It seems that parameter values like On and Off can only be changed manually or via Modbus, but not from inside the program logic (e.g., using math blocks) and I don't know how to read On value and do anything with it.

More generally – what's the recommended approach in LOGO!when you need (typical in automation?) logic like this:

• A user sets one value (e.g., via Modbus, Web Server),

• That value is retentive

• The logic internally derives related parameters or thresholds from it?

Yes, thank you.

This is exactly what I needed.

So here is my understanding of this:

- I have to take the Aq value from "parameter table" of Mathematic Instruction block, not directly from the block output

- same thing with the Analog Amplifier block and its Ax output, I need to pass the value thru this block to the P1 parameter of Mathematic Instruction

- Analog Amplifier and Mathematic Instruction blocks require some memory location to put the result to work properly, so I have to use Analog Flag blocks

So I guess that the value from some input register is not a valid location to choose as the parameter value location, but somehow some blocks also have internal memory location that can be used for that (like Aq output in Mathematic Instruction block or Ax of Analog Amplifier) because these blocks internally do something like MOV operation from input register to regular memory.

Please tell me if all above is correct.