Modbus 6-digit Address

Modbus 6-digit Addresses

At Quantum Bit Solutions, we have adopted the Modbus 6-digit address scheme for its ease of use and flexibility, moving away from the traditional 4-digit scheme (registers 1-9999).

Why Switch to the 6-Digit Address Scheme?

  1. Expanded Address Range: The 6-digit scheme supports the full 16-bit address range, from 0 to 65535 registers, as defined in the Modbus Specification. This allows for more comprehensive and scalable addressing.
  2. Simplified Addressing: The 6-digit address scheme simplifies the addressing process by combining the function code and the full address range into a single long integer value. Instead of two fields, you only need one field to specify the Function Code and Address.
  3. Consistency: In this scheme, addresses are “1-based,” meaning they start from 1, which aligns with how addresses are decoded by the Modbus Monitor Advanced, Modbus Monitor XPF, and Modbus Monitor App, along with many advanced SCADA and HMIs. This consistency makes it easier to manage and interpret addresses.

Example

The table below shows how the PLC “6-digit” address is decoded by the our Modbus Apps into the function code and the 5-digit Modbus register address:

Modbus
Register
Address
Scheme
6-Digit
Address
5-Digit
Address
4-Digit
Address1
Modbus
Function
Code
Description
10x000001000010001FC 1Read 1st Coil
11x100001100010001FC 2Read 1st Discrete Input
13x300001300010001FC 4Read 1st Input Register
14x400001400010001FC 3Read 1st Holding Register
655364x465536Not Possible2Not Possible2FC 3Read the last possible Holding register
655363x365536Not Possible2Not Possible2FC 4Read the last possible Input register
Modbus 6-Digit vs 5-digit vs 4-digit

Switching to the 6-digit address scheme will streamline your Modbus communication and enhance the overall efficiency of your PLC systems. Make the switch today for a more robust and scalable solution!

More Info: 

  1. A 4-digit code specifies the function in another field and is not included in the address, unlike the 5 and 6-digit schemes. ↩︎
  2. Only registers 1-9999 are possible. Therefore, register 65536 falls outside this range and is not possible in this scheme. The valid range is 40001 – 49999. ↩︎

Facebook
Twitter
WhatsApp
Email