ModMaster - Modbus master simulator

ModMaster is a diagnostic program that operates as a Modbus master or client. It provides all the features of Modsak's master mode, but at a lower price.

ModMaster's other main features are:

  • The user can send individual requests to a Modbus slave, and ModMaster can also continually continually poll (send read and write requests to) the slave.
  • Command (and command sequence) definitions may be saved for re-use.
  • Informative interpreted trace of Modbus messages sent and received, and of register reads and writes.
  • Optional logging of tracing and diagnostic messages to a file.
  • All configuration settings may be saved to and restored from files, in XML format.
  • Register definitions may be imported/exported in CSV format.
  • Full support for coils, discrete inputs, input registers, holding registers and file registers, using the following commands:
    • 1 Read Coils
    • 2 Read Discrete Inputs
    • 3 Read Holding Registers
    • 4 Read Input Registers
    • 5 Write Single Coil
    • 6 Write Single Holding Register
    • 7 Read Exception Status
    • 8 Diagnostics
    • 11 Get Comm Event Counter
    • 12 Get Comm Event Log
    • 15 Write Multiple Coils
    • 16 Write Multiple Holding Registers
    • 17 Report Slave ID
    • 20 Read File Record
    • 21 Write File Record
    • 22 Mask Write Holding Register
    • 23 Read/Write Multiple Holding Registers
    • 24 Read FIFO Queue
    • 43/14 Read Device Identification
    • Custom commands
    • Invalid commands - for testing the slave's error handling
  • Supports network and serial (RS232/RS422/RS485) interfaces using the following protocol variants:
    • Modbus TCP (also known as Modbus TCP/IP)
    • Modbus RTU
    • Modbus ASCII
    • Modbus RTU encapsulated in TCP
    • Modbus ASCII encapsulated in TCP
    • Modbus UDP (also known as Modbus TCP encapsulated in UDP)
    • Modbus RTU encapsulated in UDP
    • Modbus ASCII encapsulated in UDP
  • All known extensions of the Modbus protocol for handling 32-bit and 64-bit integers and floating-point numbers are supported (including Enron/Daniel Modbus).
  • Can transfer a mixture of integers and floats, of different sizes, in a single message.
  • Flexible address mapping allows separate or overlaid address spaces (for coils, discrete inputs, input registers, and holding registers) with arbitrary bases.
  • Registers are individually configurable for type (integer, unsigned integer or float), size (1/8/16/32/64-bit), radix (binary, octal, decimal, hex, or char), and scale/offset.
  • Configurable limits for register values, with highlighting of values out of range.
  • Supports broadcast requests (slave ID 0).
  • Full support for exception responses 10/0x0A ("Gateway Path Unavailable") and 11/0x0B ("Target Device Failed To Respond").
  • Cross-platform: runs on any system that supports Java JRE 1.6 or later (serial communications is only supported on Windows and Linux x86 architectures).
  • Manual and troubleshooting guide.

You can download the complete version of ModMaster for a free 3-day evaluation period.


ModMaster main window