The Modbus Holding Registers described above will be defined as Module Register Addresses and are used for the function of the regardless of if any remote PLC or PC is connected. There are 512 Module Register Addresses that are used for the operation of the and these can be thought of as “physical” module address locations. However, many of these are not applicable, required, or should even be made available to a remote PLC.
An Assembly is a grouping of some subset of these 512 Module registers based upon the relevance of the data. For example, the ZPA Input Assembly groups together 21 Module registers out of the 512 that are relevant for ZPA Inputs. This relevant data from within the Module’s 512 registers are not necessarily in consecutive address locations and are scattered throughout the 512 addresses. The Assembly groups them together so they can be read efficiently all at once.