Allen Bradley PV to PLC comms

When you create a PV project you have to use the Tags and Address from the PLC you have connected the PV to, so my question is: How does the Panel view read and write to the specified addresses? Does it directly read and write to the addresses, or is the data handled in the housekeeping, before the logic is processed?

Ultimatly I would like to know if updating the screens on the Panel Veiw is scan time dependent.

The update is done through a comm link, so the throughput on it is much slower than the PLC scan.

In general any HMI puts together inquiries for the data requested, whether direct addressed or through tags. It then sends the data inquiry to the PLC, which responds, and the HMI displays the latest data on the fields needed.

The specific HMI model, PLC model, and communications link and protocol used make a huge difference in the throughput and other important details for HMI/PLC interaction.

well Tom I gess I can elaborate, I am going to be using the ML1500 LRP with a PannelVeiw Plus 1500.

Which protocol?

Are you worried about the Panelview changing data in the middle of the program scan in the PLC?

I don't think you have to worry with a SLC/Micrologix, however a Controllogix/Compactlogix/Flexlogix, etc. is a different story...


The Micrologix/SLC program scan is:

Input Scan >>
Program Scan >>
Output Scan >>
Communications >>
Processor Overhead >> start over