> For the complete documentation index, see [llms.txt](https://docs.augelab.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.augelab.com/function-blocks/blocks-reference/input-output/communication/modbus-read.md).
# Modbus Read
This function block reads data from a Modbus server (coils or registers) using a provided Modbus client connection. Use the on-screen controls to select the target address, the number of values to read, and the Modbus data type.
## 📥 Inputs
`Enable` A boolean gate to allow or prevent reading. When False the block will not perform a read and returns no data.
`Modbus Client` Provide a Modbus client connection object (usually coming from a `Modbus Connect` block). The block uses this client to communicate with the server.
## 📤 Outputs
`Data` The read result as a generic list. For register reads this is a list of numeric register values; for coil/discrete reads this is a list of boolean values. If reading fails or is disabled, output is empty/None.
## 🕹️ Controls
`Address` Enter the start address (integer) on the Modbus device to read from.
`Quantity` Enter how many consecutive items (registers or coils) to read.
`Data Type` Choose the Modbus data type to read: Coil, Discrete Input, Input Register, or Holding Register.
## 🎯 Features
* Supports reading both bit-based (coils/discrete inputs) and word-based (input/holding registers) data types.
* Uses an external Modbus client connection provided to the `Modbus Client` input, keeping communication separate from the block’s settings.
* Simple numeric and boolean results are returned as a list suitable for logging, plotting, or downstream processing.
* Built-in error reporting surfaces communication failures so you can react (reconnect, retry, alert).
## ⚙️ Running mechanism
When active, the block checks the `Enable` input and requires a valid client on the `Modbus Client` input. It reads the configured address range using the selected `Data Type` and returns the values on the `Data` output. If the read fails or the block is disabled, it returns no data and logs a helpful error message.
## 💡 Tips and Tricks
* Use `Modbus Connect` to create and provide the required `Modbus Client` connection.
* Use `Logic Input` or `Rising Edge` to control when reads happen (manual trigger or single-shot reads).
* To write values back to a device, combine with the `Modbus Write` block.
* Log readings for later review using `CSV Export` or persist them with `Data Write Local` / `Data Write Global`.
* Visualize numeric outputs in real time by feeding numeric results into the `Scope` block.
* Use `Debug Input` to inspect and verify the returned `Data` during setup and troubleshooting.
## 🛠️ Troubleshooting
* No data returned: ensure a valid client is connected to the `Modbus Client` input and `Enable` is True.
* Wrong values or partial reads: check `Address` and `Quantity` are within the device’s address map and within device limits.
* Communication errors: verify network/serial settings via the `Modbus Connect` block and ensure no other application is blocking access.
* Unexpected data format: confirm you selected the correct `Data Type` (coils vs registers) for the values you expect.