> For the complete documentation index, see [llms.txt](https://docs.lorric.com/qr/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lorric.com/qr/fu-es-echosense-instruction-manual/communication/modbus-rtu-protocol/read-write-memory-ram.md). # Read-Write Memory (RAM)
Function CodeNameData LengthCore Purpose
03Read/Write Memory (RAM) – Read Command1~125 RegistersRead Command – Single or Multiple Holding Registers. Used to read any desired configuration parameters.
06Read/Write Memory (RAM) – Single Register Write Command

1 Registers

(16 bit)

Write Command – Single Int16 Parameter. Used to write a simple single Int16 value, suitable for setting options, codes, or small-range integers. Example: Set A08 Pipe Material to PVC (code 2).
30Read/Write Memory (RAM) – Dual Register Write Command

2 Registers

(32 bit)

Write Command – Float32 / Int32 (32-bit values). Used to write 32-bit values, such as floating-point numbers, supporting positive, negative, and fractional values approximately in the range 10⁻³⁸ to 10³⁸. Example: Set A18 Low Flow Cutoff to +5.5, or A23 Zero Offset to −0.08.
31 Read/Write Memory (RAM) – Four Register Write Command

4 Registers

(64 bit)

Write Command – Int64 (64-bit values). Used to write 64-bit values, suitable for integer parameters exceeding the 32-bit range (~4.3 billion). Example: Set D11 Total Target (64-bit) or C04 Dosing Target (64-bit) to values exceeding the 32-bit limit.
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