# Modbus RTU Protocol ## Communications format bit order: lsb first byte order: big endian Data bits:8 Parity: None Stop bits: 1 Floating point number follows IEEE754-1985. The float32 below stands for 32bits Single precision floating point number. ## Terminology ‌‌Register: Length of 2 Byte or 16bit which is unit length of memory in Modbus RTU. ‌Byte: 8 bit length ## Definition and function of memory #### **Modbus Memory Access** Modbus-accessible memory is divided into **two main categories**: **read-only** and **read/write**. * The **read-only memory** primarily contains data related to the **flow meter’s operational status**, such as **instantaneous flow rate**.\ This category is the **most commonly accessed memory area**.\ Read-only memory can **only be accessed using Function Code 04 (Read Input Registers)**. Relevant register mappings and details can be found on the following page: --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.lorric.com/qr/fp-as310-paddle-wheel-flowmeter-manual-en-v1/communication/modbus-rtu-protocol.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.