On the Modbus server-side, only 16-bit long holding and input registers are used. The 32-bit long data types are just the interpretation of the two adjacent registers. The concept of address mapping is clearly shown in the following figure. Three tables are shown there. All of them address the same place in the memory: holding registers. In the first table the holding registers are shown, in the second the 32-bit integers are shown and, in the last table, the floating-point data types are shown.