Modbus Slave Usage Guide for Modbus Testing Tools
I.Introduction to Modbus Slave
The Modbus Slave Simulator supports emulation of up to 32 slave devices/address fields, with each interface providing OLE automation support for Excel reports. Primarily designed for simulating, testing, and debugging Modbus communication devices, it replicates how slave devices receive master commands and return data packets, enabling developers to conduct protocol simulation and testing. The simulator supports up to 32 Modbus slave devices across 32 windows, featuring identical user interfaces to Modbus Poll. It supports function codes 01-23 and monitors serial port data.
II. Modbus Slave Usage
1) Install and register
Install the software. After installation, double-click the 'Modbus Slave' shortcut to execute it.
Registration procedure: Click [Connection] → [Connect] to open the registration window. Extract the readme file from the compressed package, copy the serial number of Modbus Poll, and paste it into the registration field. Click OK to complete the cracking process.
The installation and configuration of Modbus Slave are similar to Modbus Poll, so we won't repeat the details here.
2)Main program window
The software main window is shown below:
The system is currently in the 'No connection' state. If only the '04 output hold register' needs testing, you can skip to step 3 and proceed directly with the connection.
3）Parameter Settings
Click the menu [Setup] -> [Slave Definition] to configure parameters, and a parameter setup dialog box will appear.
Among:
①Slave ID refers to the Modbus slave address, corresponding to the ID value in the main interface, with a default value of 1.
②Function refers to the selection of register function codes, with four types available, corresponding to the following relationships:
|
code |
name |
Register PLC address |
bit operation/ word operation |
Operation count |
|
01 |
Read coil status |
00001-09999 |
bit manipulation |
Single or multiple |
|
02 |
read discrete input state |
10001-19999 |
bit manipulation |
Single or multiple |
|
03 |
read hold register |
40001-49999 |
Word operations |
Single or multiple |
|
04 |
read input register |
30001-39999 |
Word operations |
Single or multiple |
|
05 |
Write a single coil |
00001-09999 |
bit manipulation |
single |
|
06 |
Write to a single hold register |
40001-49999 |
Word operations |
single |
|
15 |
Write multiple coils |
00001-09999 |
bit manipulation |
multiple |
|
16 |
Write multiple hold registers |
40001-49999 |
Word operations |
multiple |
③Address is the register's starting address, defaulting to 1.
④Quantity refers to the number of consecutive registers, with a default value of 10.
After completing the setup, click the OK button. The simulation window will display the list of defined registers.
Among:
①ID denotes the device address of the simulated Modbus sub-device;
②F denotes the function code. Clicking the corresponding register allows modification of its value or status. For example, changing register 2's value to 9 or register 9's value to 100.
4）Display settings
①Data display settings:
By default, register data is displayed in Signed format (16-bit unsigned binary) with a range of-32768 to 32767. To display data in other numerical formats, users can select the option through the [Display] menu as shown in the figure below:
② Address format settings
Modbus Slave devices use PLC addresses by default. The [PLC Addresses (Base 1)] option in the [Display] menu is preselected, with default registers starting from address 1. This configuration aligns with the Modbus serial port and TCP data forwarding driver in configuration software. For testing purposes requiring zero-based initialization, select [Protocol Addresses (Base 0)]. The default PLC address settings are generally sufficient for most applications.
5)Connection
Click the menu [Connection] -> [Connect] to connect. A connection dialog box will appear:
Among:
①Port2 indicates the serial port (COM2) used. Select either a different serial port or TCP/IP for connection based on actual requirements.
②Mode indicates the Modbus protocol mode, valid when using serial port and automatically switches to TCP mode when using TCP/IP.
③Flow Control refers to flow control, which is active in serial port mode.
④Ignore Unit ID means ignoring invalid group IDs when operating in TCP mode
Users can configure parameters as needed. The default settings are: Serial port 1, baud rate 9600,8-bit data width, no parity bit, and 1-stop bit. After confirming the settings, click the "OK" button. The red "No connection" message in the main window will disappear, indicating that the slave station is now connected.
6)Register value change
Double-click the main window register address to open the modification dialog box, as shown below:
Enter the value in the input box to confirm. The range is-32768 to 32767. When the Auto increment option is selected, the corresponding register value increases by 1 every second.
7）Check communication data frames
Click [Communication] in the [Display] menu to open the serial port data frame monitoring dialog box for viewing and analyzing transmitted/received data frames, as shown in the figure below.
The first six digits represent the sequence number of the data frame, where Rx denotes the received data frame and Tx indicates the transmitted data frame.
8 )Disconnect
Click [Connection] → [Disconnect] to disconnect and end the test. A red "No connection" will appear in the main window, indicating the disconnected state.