# modbus.crc16

## Function

Calculate Modbus RTU CRC16.

## Syntax

```bt
modbus.crc16(data)
```

## Parameters

| Parameters | Type | Required | Default value | Description |
|------|------|------|------|------|
| data | Bytes/Array/String | Yes | None | Bytes involved in CRC calculation, excluding frame tail CRC. |

## Return value

| Type | Description |
|------|------|
| Int | CRC16 value. Low byte first when writing RTU frames. |

## Code Example

```bt
value = modbus.crc16(bytes('01030000000a', 'hex'))

// Output: 52677
print value
```

## Notes

- `crc16()` only returns a numerical value; when building an RTU request, please use `rtu_request()` first to automatically write the CRC.