> For the complete documentation index, see [llms.txt](https://help.novacuraflow.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.novacuraflow.com/6.11/development/flow-studio/connectors/communication/modbus/read-operations.md).

# Read operations

### Read Coils <a href="#read-coils" id="read-coils"></a>

Reads Coils

#### Parameters <a href="#parameters" id="parameters"></a>

| Parameter                       | Description                                                                                                  |
| ------------------------------- | ------------------------------------------------------------------------------------------------------------ |
| First Address to be read        | Address from where the data read begins.                                                                     |
| Number of addresses to be read  | Length of data.                                                                                              |
| Slave Address / Unit identifier | Unit identifier (previously slave address). In asynchonous mode this unit is given to the callback function. |

#### Output <a href="#output" id="output"></a>

Returns a table with values, true or false.

#### Since <a href="#since" id="since"></a>

6.4

### Read Digital Inputs <a href="#read-digital-inputs" id="read-digital-inputs"></a>

Read Digital Inputs

#### Parameters <a href="#parameters" id="parameters"></a>

| Parameter                       | Description                                                                                                  |
| ------------------------------- | ------------------------------------------------------------------------------------------------------------ |
| First Address to be read        | Address from where the data read begins.                                                                     |
| Number of addresses to be read  | Length of data.                                                                                              |
| Slave Address / Unit identifier | Unit identifier (previously slave address). In asynchonous mode this unit is given to the callback function. |

#### Output <a href="#output" id="output"></a>

Returns a table with values, true or false.

#### Since <a href="#since" id="since"></a>

6.4

### Read Holding Register <a href="#read-holding-register" id="read-holding-register"></a>

Read Holding Register

#### Parameters <a href="#parameters" id="parameters"></a>

| Parameter                       | Description                                                                                                  |
| ------------------------------- | ------------------------------------------------------------------------------------------------------------ |
| First Address to be read        | Address from where the data read begins.                                                                     |
| Number of addresses to be read  | Length of data.                                                                                              |
| Slave Address / Unit identifier | Unit identifier (previously slave address). In asynchonous mode this unit is given to the callback function. |

#### Output <a href="#output" id="output"></a>

Returns a table with values.

#### Since <a href="#since" id="since"></a>

6.4

### Read Input Register <a href="#read-input-register" id="read-input-register"></a>

Read Input Register

#### Parameters <a href="#parameters" id="parameters"></a>

| Parameter                       | Description                                                                                                  |
| ------------------------------- | ------------------------------------------------------------------------------------------------------------ |
| First Address to be read        | Address from where the data read begins.                                                                     |
| Number of addresses to be read  | Length of data.                                                                                              |
| Slave Address / Unit identifier | Unit identifier (previously slave address). In asynchonous mode this unit is given to the callback function. |

#### Output <a href="#output" id="output"></a>

Returns a table with values.

#### Since <a href="#since" id="since"></a>

6.4


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