Supported features

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Last UpdatedSep 26, 2025
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The Modbus TCP EDS (Edge Data Store) adapter collects data using register types and then converts the registers into data types. It can apply bitmaps and data conversion to values converted from reading the Modbus TCP devices.

Definition: Modbus TCP, Transmission Control Protocol, is a Modbus variant used for communications over TCP/IP networks, connecting over port 502. It does not require a checksum calculation, as lower layers already provide checksum protection.

Modbus Security

The Modbus TCP EDS adapter supports secure Modbus communication over TLS in accordance with the Modbus TCP/Security specification.

Register types

The Modbus TCP EDS (Edge Data Store) adapter supports 6 register types, corresponding to 4 function codes (1-4). Since one function code can return two types of registers, either 16-bit or 32-bit depending on the device, either the register type or the register type code is required when configuring the data selection for the adapter.

The following table lists all the register types supported in the Modbus TCP EDS (Edge Data Store) adapter.

Register Type	Register Type Code	Description	Function Code
Coil	1	Read Coil Status	1
Discrete	2	Read Discrete Input Status	2
Holding16	3	Read 16-bit Holding Registers	3
Input16	6	Read 16-bit Input Registers	4

When reading from function codes 1 and 2, the adapter expects these to be returned as single bits. For function codes 3 and 4, the adapter expects 16 bits to be returned from devices that contain 16-bit registers and 32 bits to be returned from devices that contain 32-bit registers.

Data types

The Modbus TCP EDS (Edge Data Store) adapter converts readings from single or multiple registers into the data types specified by the data type code and populates the value into streams created in the Edge Data Store (EDS (Edge Data Store)).

The following table lists all data types with their corresponding type codes supported by the Modbus TCP EDS (Edge Data Store) adapter.

Data type code	Data type name	Value type	Register type	Description
1	Boolean	Boolean	Bool	0 = false 1 = true
10	Int16	Int16	Bool/16-bit	Read 1 Modbus TCP register and interpret as a 16-bit integer. Bytes [BA] read from the device are stored as [AB]. Definition: Modbus TCP, Transmission Control Protocol, is a Modbus variant used for communications over TCP/IP networks, connecting over port 502. It does not require a checksum calculation, as lower layers already provide checksum protection.
20	UInt16	UInt16	Bool/16-bit	Read 1 Modbus TCP register and interpret as an unsigned 16-bit integer. Bytes [BA] read from the device are stored as [AB]. Definition: Modbus TCP, Transmission Control Protocol, is a Modbus variant used for communications over TCP/IP networks, connecting over port 502. It does not require a checksum calculation, as lower layers already provide checksum protection.
30	Int32	Int32	16-bit/32-bit	Read 32 bits from the Modbus TCP device and interpret as a 32-bit integer. Bytes [DCBA] read from the device are stored as [ABCD]. Definition: Modbus TCP, Transmission Control Protocol, is a Modbus variant used for communications over TCP/IP networks, connecting over port 502. It does not require a checksum calculation, as lower layers already provide checksum protection.
31	Int32ByteSwap	Int32	16-bit/32-bit	Read 32 bits from the Modbus TCP device and interpret as a 32-bit integer. Bytes [BADC] read from the device are stored as [ABCD]. Definition: Modbus TCP, Transmission Control Protocol, is a Modbus variant used for communications over TCP/IP networks, connecting over port 502. It does not require a checksum calculation, as lower layers already provide checksum protection.
40	UInt32	Int32	16-bit	Read 32-bits from the Modbus TCP device and interpret as a 32-bit unsigned integer. Bytes [DCBA] read from the PLC are stored as [ABCD].
41	UInt32ByteSwap	Int32	16-bit	Read 32-bits from the Modbus TCP device and interpret as a 32-bit unsigned integer. Bytes [BADC] read from the PLC are stored as [ABCD].
100	Float32	Float32	16-bit/32-bit	Read 32 bits from the Modbus TCP device and interpret as a 32-bit float. Bytes [DCBA] read from the device are stored as [ABCD]. Definition: Modbus TCP, Transmission Control Protocol, is a Modbus variant used for communications over TCP/IP networks, connecting over port 502. It does not require a checksum calculation, as lower layers already provide checksum protection.
101	Float32ByteSwap	Float32	16-bit/32-bit	Read 32 bits from the Modbus TCP device and interpret as a 32-bit float. Bytes [BADC] read from the device are stored as [ABCD]. Definition: Modbus TCP, Transmission Control Protocol, is a Modbus variant used for communications over TCP/IP networks, connecting over port 502. It does not require a checksum calculation, as lower layers already provide checksum protection.
110	Float64	Float64	16-bit/32-bit	Read 64 bits from the Modbus TCP device and interpret as a 64-bit float. Bytes [HGFEDCBA] read from the device are stored as [ABCDEFGH]. Definition: Modbus TCP, Transmission Control Protocol, is a Modbus variant used for communications over TCP/IP networks, connecting over port 502. It does not require a checksum calculation, as lower layers already provide checksum protection.
111	Float64ByteSwap	Float64	16-bit/32-bit	Read 64 bits from the Modbus TCP device and interpret as a 64-bit float. Bytes [BADCFEHG] read from the device are stored as [ABCDEFGH]. Definition: Modbus TCP, Transmission Control Protocol, is a Modbus variant used for communications over TCP/IP networks, connecting over port 502. It does not require a checksum calculation, as lower layers already provide checksum protection.
1001 - 1250	String	String	16-bit/32-bit	1001 reads a one-character string, 1002 reads a two-character string, and 1003 reads a three-character string and so on. Bytes [AB] are interpreted as "AB".
2001 - 2250	StringByteSwap	String	16-bit/32-bit	2001 reads a one-character string, 2002 reads a two-character string, and 2003 reads a three-character string and so on. Bytes [BA] are interpreted as "AB".

Apply bitmap

The Modbus TCP EDS (Edge Data Store) adapter supports applying bitmaps to the value converted from the readings from the Modbus TCP devices. A bitmap is a series of numbers used to extract and reorder bits from a word register. The format of the bitmap is uuvvwwxxyyzz, where uu, vv, ww, yy, and zz each refer to a single bit. A leading zero is required if the referenced bit is less than 10. The low-order bit is 01 and high-order bit is either 16 or 32. Up to 16 bits can be referenced for a 16-bit word (data types 10 and 20) and up to 32 bits can be referenced for a 32-bit word (data type 30 and 31). For example, the bitmap 0307120802 maps the second bit of the original word to the first bit of the new word, the eighth bit to the second bit, the twelfth bit to the third bit, and so on. The high-order bits of the new word are padded with zeros if they are not specified.

Not all data types support applying bitmap. The data types supporting bitmap are:

Int16 (Data type code 10)
UInt16 (Data type code 20)
Int32 (Data type code 30 and 31)

Apply data conversion

The Modbus TCP EDS (Edge Data Store) adapter supports applying data conversion to the value converted from reading the Modbus TCP devices. A conversion factor and conversion offset can be specified. The conversion factor is used for scaling the value up or down, and the conversion offset is used for shifting the value. The mathematical equation used in conversion is the following:

<After Conversion> = <Before Conversion> / Factor - Offset

Not all data types support applying data conversion. Data types that support data conversion are:

Int16 (Data type code 10)
UInt16 (Data type code 20)
Int32 (Data type code 30 and 31)
Float32 (Data type code 100 and 101)

The value with data conversion applied will always be converted to the 32-bit float type to maintain the precision of the conversion factor and conversion offset.

Edge Data Store