Standard Address Mapping in Modbus RTU

There is no default map for all devices, it's based on the memory map of device you wish to speak to. The address depends on the target device. For example, if the target is a PLC you can access any 4x address with the MSTR instruction. A VFD with Modbus or Modbus Plus can provide certain data as 4x addresses. The addressing is going to vary based on the target device. Look to the manufacturer of the device you want to speak TO for a map of it's memory.