What is a Modbus poll?
Ⅰ.Introduction to Modbus Poll
Modbus Poll is a Modbus host simulator designed for testing and debugging Modbus slave devices. Supporting Modbus RTU, ASCII, and TCP/IP protocols, this software assists developers in testing Modbus slaves or simulating other Modbus protocols. It features a multi-document interface enabling simultaneous monitoring of multiple slave devices/data fields. Each window allows configuration of slave device ID, functions, address, size, and polling intervals, with register and coil access from any window. To modify individual registers, simply double-click the value; multiple registers/coils can be adjusted simultaneously. Modbus Poll also supports various data formats including floating-point, double-precision, and long integer types (with byte sequence swapping capability).
Ⅱ. Modbus Poll Usage
1) Install and register
After installation, you'll see a shortcut for Modbus Poll on your desktop. Double-click it to launch the software, which displays the interface as shown below.
Click [Connection] → [Connect] to open the registration window. Open the decompressed readme file from the compressed package, copy the serial number of Modbus Poll, and paste it into the registration field. As shown in the figure below, click OK to complete the cracking process.
2) Follow the above cracking procedure in the program's main window and click the "OK" button to complete registration.
Then proceed directly to the main window as shown in the figure below.
The parameters are defined as follows:
①Tx = 0 indicates the number of data frames transmitted to the master station (shown as 0 in the diagram);
②Err = 0 denotes the number of communication errors (also shown as 0);
③ID = 1 represents the device address of the simulated Modbus slave device (displayed as 1 in the diagram);
④F = 03 indicates the Modbus function code used (shown as function code 03 in the diagram);
⑤SR = 1000ms specifies the scanning cycle duration;
⑥The red-marked sections indicate current error statuses, with "No Connection" indicating an unconnected state.
3) parameter setting
click the menu [Setup] → [Read/Write Definition]. A parameter configuration dialog box will appear.
The parameters are defined as follows:
①Slave ID refers to the address of the Modbus slave device to be accessed, corresponding to the ID value in the main interface (master screen), with a default value of 1.
②Function refers to the selection of register function codes, with four types available, corresponding to the following relationships:
③Address is the register's starting address, defaulting to 0.
④Quantity refers to the number of consecutive registers, with a default value of 10, matching the channel count in the configuration software.
⑤Scan Rate refers to the data reading cycle in milliseconds, with a default value of 1000ms.
After completing the setup, click the OK button. The simulation window will display the list of defined registers.
4) Display settings
①Data display mode: By default, register data is displayed in Signed format (16-ary unsigned binary), with a range of-32768 to 32767. Users may select alternative numerical display formats via the [Display] menu, as shown in the figure below:
②Address format configuration
Modbus Slave defaults to PLC addresses. 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 address 0-based initialization, select [Protocol Addresses (Base 0)]. The default PLC address configuration is generally sufficient.
③ Communication command settings
The [Communication Traffic] button on the toolbar displays the currently sent commands and received data.
5) connect
Click the Connection menu-> Connect to establish a connection, as shown in the figure below:
The parameters are defined as follows:
①Serial Settings indicates the serial port (COM1) used. Depending on actual requirements, select different serial ports or TCP/IP for connection.
②Mode indicates the Modbus protocol mode, valid when using a serial port, and automatically switches to TCP mode when using TCP/IP.
③Response Timeout indicates the read timeout duration. If no data is returned by the station within this time limit, the communication is deemed failed.
④Delay Between Polls specifies the minimum interval between scans, with a default value of 10ms.
⑤Remote Modbus Server refers to the network configuration of the terminal slave device in TCP/IP mode.
⑥IP Address or Node Name indicates the slave IP address in TCP/IP mode.
⑦Server Port indicates the slave network port in TCP mode.
Users can configure parameters as needed. The default settings are: Serial port 1, baud rate 9600,8-bit data, no parity bit, and 1-stop bit. After confirming the settings, click the OK button. If the connection and reading are correct, the main window will display the relevant information from the read register.
6) To modify register values
double-click the main window register address to open the modification dialog box, as shown in the figure below:
①Slave ID refers to the Modbus slave address to be accessed, corresponding to the ID value in the main interface, with a default value of 1.
②Address refers to the register address for the current operation, as shown in the diagram where register 40001 is being manipulated.
③Value: Enter the value in the input box to confirm. The range is-32768 to 32767.
④Use Function refers to the function code used, with options of 06 or 16 for writing.
7)To view communication data frames
select [Communication] from the [Display] menu or click the [] button on the toolbar to open the serial port data frame monitoring dialog box "Communication Traffic", which allows you to view and analyze 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 terminate the connection and end the test. A red "No Connection" will then appear in the main window, indicating the disconnected state.