Busscope

Busscope Slave: Modbus slave simulator for Windows

Simulate Modbus devices, and break them on purpose.

Busscope Slave answers like real devices over Modbus TCP and RTU, so you can test masters, SCADA and PLC programs without the hardware. Change values live and inject faults to see how your master copes.

Request the evaluation See pricing

Current version 0.2.0. The installer is not published yet: write to us for the evaluation build.

Busscope Slave with the Values tab: slave ID 1 of a simulated pump station with named holding registers (flow, pressure, temperature, speed), and the communication traffic below

Features

What Busscope Slave does

  • 2transports: TCP and RTU
  • 247slave ids behind one connection
  • 5fault kinds you can inject
  • 5patterns for changing values

Several slaves, one connection

Add as many slave ids as you need. Each slave has its own coils, discrete inputs, holding registers and input registers, up to 65,536 of each.

  • Edit values in a table, in the display format you need
  • Name the rows, so the table reads like the device documentation
  • A master's write shows up in the table at once
Busscope Slave with the Values tab: slave ID 1 of a simulated pump station with named holding registers (flow, pressure, temperature, speed), and the communication traffic below
Values and traffic

Fault injection

Make a slave misbehave on purpose and watch your master. Each rule says which requests it applies to and what goes wrong.

  • Answer with an exception code, answer late, never answer, damage the frame check or send half an answer
  • Limit a rule to a slave id, a function code, an address range and a probability
  • A counter per rule shows how often it fired
The Faults tab of Busscope Slave with four rules: an exception on slave 1, a delay on slave 2, dropped replies on slave 3 and a disabled corrupt rule, each with its hit counter
Fault rules with hit counters

Values that change by themselves

Give your master something live to read. Registers can ramp, swing as a sine wave, wander as a random walk or count; bits can toggle.

  • Any numeric format, including Float, with a low and high limit
  • One cycle time or step per generator
  • A master's write to such a value is overwritten at the next update
The Changing values tab of Busscope Slave with sine, random walk, ramp and counter generators on slave 1 and slave 2
Changing values

And the details that save time

Modbus TCP server

Listens on a port of your choice (502 by default). It binds 127.0.0.1, so only this computer can reach it, until you choose 0.0.0.0 and confirm.

Modbus RTU on a serial port

Real COM port or a virtual COM pair. Baud rate, parity, data and stop bits, and a frame gap you can raise for USB adapters and virtual ports.

Traffic view

Every request with the slave id, function, address and what the slave answered, including exceptions and unanswered requests. Raw frames for serial.

Setup files

Save slaves, values, names, fault rules and changing values as a .bss file and load the same test bench again later.

Local by default

Nothing is sent to any server. Busscope Slave only talks to the Modbus masters that connect to it.

For any Modbus master

Your SCADA, a PLC program, a script or Busscope Master: if it speaks Modbus TCP or RTU, it can connect.

Busscope Slave pricing

Same prices as Busscope Master. One perpetual license, with volume prices for teams. Busscope Slave has its own license key, delivered by email. Details and how licensing works.

1 user

$69 $39 per user

Launch price until 31 December 2026, then $69 per user.

For one person, on all their computers. Perpetual license, key by email.

Request a license

2-5 users

$59 $35 per user

Launch price until 31 December 2026, then $59 per user.

For small teams: one key, one invoice. Same perpetual license.

Request a license

6 or more users

$50 $29 per user

Launch price until 31 December 2026, then $50 per user.

For larger teams: the lowest price per user. Same perpetual license.

Request a license

Questions about licenses: support@busscope.com.

Evaluate it first

Without a license key Busscope Slave runs in evaluation mode for 14 days with everything switched on. Afterwards the simulator keeps working, but fault injection and changing values switch off and each connection stays up for 15 minutes (connect again to continue). Evaluation use for production or commercial purposes is not permitted.

Request the evaluation

Frequently asked questions

Do I need a real device to test against?

No. Busscope Slave plays the device. A Modbus TCP master on the same computer connects to 127.0.0.1. For Modbus RTU use a real COM port or a virtual COM pair.

Can it simulate more than one device?

Yes. Add as many slave ids (1 to 247) as you need behind one connection. Each has its own coils, discrete inputs, holding registers and input registers.

Can it make a device misbehave on purpose?

Yes. Fault rules answer with an exception code, answer late, never answer, damage the frame check or send only half of the answer. A rule can be limited to a slave id, a function code, an address range and a probability.

What happens after the evaluation ends?

The simulator itself keeps working: TCP and RTU, several slaves, editing values, the traffic view and setup files. Fault injection and changing values switch off, and each connection stays up for 15 minutes; connect again to continue. Your rules stay saved.

Is Busscope Slave safe to run on a network?

By default it listens on 127.0.0.1, so only programs on the same computer can connect. Listening on 0.0.0.0 makes it reachable from the network and the program asks you to confirm first.

Does a Busscope Master license also unlock Busscope Slave?

No. Busscope Slave is a separate product with its own license key. The prices are the same as for Busscope Master.