The diagrams below indicate the example choices of AC500 CPU's (horizontal axes) based on the number of communication interface CI-remote I/O clusters ( Communication Interface modules; numbers see legend) used in a system and resulting application cycle times (vertical axes).

Further details can be found in 'Task configuration recommendations for HA system'⮫ “Task configuration recommendations for HA system”. The values in below graphs base on the assumption to use max. 50-60% as CPU loading by the bare fast IO communication and HA functionality. So the application load would come on top and cycle times (especially HA, Modbus) need to be relaxed (made higher) compared to below indication.

Example: If you need a system supporting min. 25 CI at application cycle time around 120 ms, suitable options based on above graph would be V2 PLCs - PM592 or PM595 and V3 PLCs – PM5650 or PM5670. The main parameter in the application cycle determination is the amount of overall Sync data, which is assumed 160 bytes per CI for the smaller systems, up to 250 bytes per CI for the larger ones. Sync data of the project of in total more than ~1200 byte necessitates several HA cycles to transfer within one application cycle.

If CM5640-2ETH port extender is used for the CI network, slightly lower performance/longer cycle time needs has to be expected.

The V2 or V3 PLCs types, also differ in available interfaces, protocols supported and memory size.

CI521-MODTCP or CI522-MODTCP can be used as peripheral devices which communicate via the Modbus TCP protocol with the PLCs. The HA-Modbus TCP library supports currently up to 120 CI52x, depending on the CPU type as listed in table 'Overview of AC500 HA systems and options'⮫ Further information. Each CI52x supports up to a maximum of 10 S500-I/O modules. Nevertheless the standard Modbus TCP communication of the HA library transfers only 120 words per cycle: Therefore please check if for your module configuration matches: In case of many analog IO modules with high-density - like 16 channel AI523/AO523 or modules with fast counters - this limit might be surpassed by roughly 5-6 such modules (to help calculate exactly, there is an Excel sheet provided in the HA “Examples” subfolder of Automation Builder once installed).

⮫ More details on supported Modbus clients.