HMI software mechanism

What is the mechanism the HMI captures a plant-event?. Some context below:
1.- a dry contact provides a digital input to the RTU. I guess this RTU or PLC keeps monitoring its inputs by using a close loop like:

while(true){—code here—}

2.- once the PLC /RTU capture a data then it is sent via protocol to the HMI-DATABASE which stablishes communication and receives the new data base (updated) from the RTU/PLC. the HMI data base then reads the points and update the display.

is it correct??? please help.

Hey @iochoa2020 , welcome to the SolisPLC community forum :wave:

I think that @VRomanov can help you with this :slight_smile:


What you’ve described is correct. It’s important to note that the PLC can choose how the data is sent to the HMI. Typically, you don’t always send the raw value directly to the HMI. At the very least, it is scaled to a “human understandable” register. In other words, the following happens:

  1. The Analog sensor (RTU) is connected to an analog input on a PLC. It continuously updates the raw value register on the PLC.
  2. The PLC will contain logic that will convert the data in the raw value register to a scaled register.
  3. The HMI will read the register contents in the scaled register value and update the screens accordingly.
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