Online MODBUS RTU Register Memory Map Scanner
How the MODBUS Memory Scanning Procedure Works
The utility utilizes a specialized programming interface (Web Serial API) to facilitate COM port communication directly from the browser and retrieve data from a MODBUS device.
Upon initializing the port, the program reads two registers at a time (to optimize performance), beginning at offset 0. To terminate the search, simply close the port.
Key Advantages
The primary advantage is the elimination of the need to install specialized software, drivers, or third-party libraries.
Directly from your browser, you can map the registers of your device on an RS-485 bus or via a direct RS-232 connection. This ensures a cross-platform experience: the same utility functions seamlessly on Windows, macOS, and Linux (using Chromium-based browsers such as Google Chrome, Microsoft Edge, or Opera). For field work where only a regular laptop or an Android tablet might be available, this portability is very important.
MODBUS COM Port Connection
Feature Not Supported
Your current browser does not support the Web Serial API required to access local COM ports. Please use a Chromium-based browser like Google Chrome, Microsoft Edge, or Opera.
Security
Interacting with serial ports via a browser and the Web Serial API involves strict security protocols designed to protect the user.
Key security aspects include:
Exclusive user consent: This page cannot autonomously access the list of available ports. Port connection is initiated only after the user triggers an action (e.g., clicking "Connect") and selects a specific device within the system dialogue box.
Isolation and HTTPS: The API is restricted to secure contexts (HTTPS). This encrypted connection prevents data interception or spoofing between the browser and the hardware.
Background operation restriction: Access to the port is immediately revoked once the tab is closed. This prevents unauthorized background monitoring or device control.
Complete specifications and security requirements are published in the official W3C document: Web Serial API.
Which Serial Ports are Supported?
The utility is compatible with all serial ports recognized by your operating system. The browser will present a selection window containing all available ports; the utility only gains access to the specific port you authorize.
How Long Does Register Mapping Take?
The utility sends a request to read holding registers and waits one second for a response. If the initial request fails, a second attempt is made. Scanning the entire memory range from 0 to 65535 may take up to 100 minutes.
If the device returns consecutive error codes, the program assumes the end of the data region has been reached and terminates the scan.
Can the Utility Read All Device Values?
The utility performs a sequential memory read starting from offset 0. If the device memory is segmented, the utility may not reach subsequent data segments.
For specific electricity meters with a MODBUS interface, the application can read MODBUS data online using a predefined register map.
Why Does the Utility Read Two Registers at a Time?
Certain devices do not support large data blocks or impose specific constraints. This block size was selected to ensure maximum compatibility across a wide range of hardware.
How Do I Find the Device Address?
We provide an online MODBUS device discovery utility that identifies devices by iterating through all possible addresses.