LXM32M | 3 Basics |
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3.4.4"Function Code" 23 (ReadWrite Multiple Registers)
This "Function Code" 23 (ReadWrite Multiple Registers) allows you to read and write several consecutive parameters, starting at any address.
Modbus request Structure of the Modbus request:
Field | Bytes | Value | Meaning |
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Function Code | 1 | 23 = 17h | Read/Write Multiple Registers |
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Read Starting | 2 | (various) | Address of the first parameter to be read |
Address |
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Quantity To Read | 2 | 2 * n | Number of 16 bit values to be read |
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| (1 parameter has the value 2 since a parameter |
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| consists of a 32 bit value) |
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Write Starting | 2 | (various) | Address of the first parameter to be written |
Address |
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Quantity To Write | 2 | 2 * m | Number of 16 bit values to be written |
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| (1 parameter has the value 2 since a parameter |
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| consists of a 32 bit value) |
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Write Byte Count | 1 | 4 * m | Number of data bytes |
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Write Registers | 4 * m | (various) | Parameter values |
Value |
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Modbus response Structure of the positive Modbus response:
Field | Bytes | Value | Meaning |
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Function Code | 1 | 23 = 17h | Read/Write Multiple Registers |
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Byte Count | 1 | 2 * n | Number of data bytes |
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Read Registers | 2 * n | (various) | Parameter values |
Value |
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Structure of the negative Modbus response
Field | Bytes | Value | Meaning |
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Function Code | 1 | 17h + 80h = 97h | Read/Write Multiple Registers |
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Exception Code | 1 | 01h ... 04h | See chapter |
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| "3.3.2 Modbus response to a Modbus request" |
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0198441113843, V1.01, 01.2012
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