Help regarding HMI - PLC

hello all, im currently an electrical apprentice at a manufacturing company in australia.

in the coming weeks i should get some exposure to HMI programming but id like to get a bit more background knowledge beforehand.

from what i can gather, the actual HMI design is pretty easy. using simple MS Paint-like designs to create the design interface on the HMI. Then am i correct in saying that once the operator selects an input on the HMI, it sends an array to the PLC and the PLC opens the array of words/double words etc. then during its scan cycle updates the outputs and then sends an array back to the HMI and the HMI opens the array into the double words etc and updates its status on the HMI.

thats my understanding on the process, im not even sure if im right. but if someone could correct me or show me a good helpful webpage id be much appreciative.

the PLC's we use are allen bradley and the HMI program is factory talk im lead to believe.

Thanks guys.

No, most of the traffic is the HMI asking the PLC to send it the values of data stored in the PLC. What that data is is determined by what has been programmed (by you) in the HMI display.

A much smaller amount of data is the HMI sending data (push button presses, analog numbers, etc) that the operator has activated on the HMI display. Not all operator interaction is sent to the PLC.

An overview but most, if not all HMIs, work this way. Sometimes its multiple PLCs, sometimes its not PLCs at all but other smart devices.

MS Paint objects can be displayed but most of the time you'll use HMI objects - push buttons, analog indicators, etc. that have to be configured for how they operate and which data they will interact with in the PLC.