Modbus Addressing Offset

Question:

The TOP Server suggests the following Modbus addressing:

• Output Coils: 000001 - 065536
• Input Coils: 100001 - 165536
• Internal Registers: 300001 - 365536
• Holding Registers: 400001 - 465536

but the device suggests the following addressing:

• Output Coils: 00001 - 09999
• Input Coils: 10001 - 19999
• Input Registers: 30001 - 39999
• Holding Registers: 40001 - 49999

How do I make the two address maps coincide?

Answer:

The first number 0-4 identifies the Modbus memory type, and the following numbers identify the offset for that memory type. The TOP Server supports offsets up to 65535 into Modbus memory locations which are supported in some Modbus devices.