Online Modbus, Modbus-RTU

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Modbus Dry-Run Analyzator

This tool allows and helps you to understand Modbus-Master Request and Modbus-Slave response. Also for debugging purposes.

In the modbus 'realtime live sampler' section you are able to use your computer as Serial-Over-Internet, and run queries directly to your device.

Modbus-Master Request

    0x01 Read Coil Status         Start Address: 0
    0x02 Read Input Status        Start Address: 10001
    0x03 Read Holding Registers   Start Address: 40001
    0x04 Read Input Registers     Start Address: 30001

Decimal: 202 or Hex: 0x00CA

Usually: 2 or 1

Paste your hexadecimal string here to parse

    Slave ID:                1 (decimal) |   01 (hexadecimal)
    Function:                3 (decimal) |   03 (hexadecimal)
    Register Offset:       305 (decimal) | 0131 (hexadecimal)
    Number Of Registers:    30 (decimal) | 001E (hexadecimal)

    CRC:                 61845 (decimal) | 95F1 (hexadecimal)
    CRC Should Be:       61845 (decimal) | 95F1 (hexadecimal)

    Request: [01] [03] [0131] [001E] [95F1]
             |    |    |      |      |-> CRC16 (61845)
             |    |    |      |-> Number Of Registers (30)
             |    |    |-> Register Offset (305 = 40306)
             |    |-> Function Code (3)
             |-> Slave ID (1)

Modbus-Master Response

    Data Types:
         [char]      8bit,  1 byte  0-255,        (-)127-127
        [short]      16bit, 2 byte  0-65535,      (-)32767-32767
         [long]      32bit, 4 byte  0-4294967296, (-)2147483647-2147483647
        [float]      32bit, 4 byte                (-)2147483647-2147483647

        [long64]      64bit, 8 byte          2^64,     ((2^64 - 1) / 2)
        [double]      64bit, 8 byte          2^64,     ((2^64 - 1) / 2)

    Slave ID:                1 (decimal) |   01 (hexadecimal)
    Function:                3 (decimal) |   03 (hexadecimal)
    Number of Bytes:         2 (decimal) |   02 (hexadecimal)

    CRC:                 61605 (decimal) | A5F0 (hexadecimal)
    CRC Should Be:       61605 (decimal) | A5F0 (hexadecimal)
    One Register Size:    2Byte - 16bit

    Request: [01] [03] [02] [DATA] [A5F0]
             |    |    |    |      |-> CRC16 (61605)
             |    |    |    |->  2E30
             |    |    |-> Byte Count (2)
             |    |-> Function Code (3)
             |-> Slave ID (1)

    Data: Row Format: Data Type, Signed, Unsigned

        (0)  (short)    11824     11824
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