Siemens S7 Nodes

Communicate with Siemens S7-300, S7-400, S7-1200, and S7-1500 series PLCs through dedicated read, write, and system nodes optimized for deterministic industrial control.

Configuration Quick Reference

Field	What you choose	Details
Parameters	Connection, Function, Function Parameters, Timeout Override	Select the connection profile, function, configure function parameters with expression support, and optionally override timeout.
Settings	Description, Timeout (seconds), Retry on Timeout, Retry on Fail, On Error	Node description, maximum execution time, retry behavior on timeout or failure, and error handling strategy. All execution settings default to pipeline-level values.

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S7 Read Node

S7 Read Node

Read data from Siemens PLC data blocks and memory areas with optimized batch reading.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Read Data Block Multi (s7.read.db.multi)	Fetch multiple data points from a single DB	Recipes, production counters, configuration
Read Memory Area Multi (s7.read.memory.multi)	Read multiple data points from M, I, or Q areas	Interlocking, diagnostics, status dashboards

Node Configuration

Parameter	Type	Required	Description
Connection	Selection	Yes	S7 connection profile to use
Function	Selection	Yes	Read function from the selected connection
Function Parameters	Dynamic	Varies	Auto-populated from the function schema. See your S7 connection functions for full parameter details.
Timeout Override	Number (seconds)	No	Override the default function timeout

All function parameters support expression syntax ({{ expression }}) for dynamic values from the pipeline context.

Input

The node receives the output of the previous node as input. Input data can be referenced in function parameter expressions using $input.

Output Structure

On success the node produces:

{
  "result": { ... },
  "_metadata": { "success": true, "functionId": "<function-id>", "durationMs": 42, "timestamp": "2026-01-15T08:30:00Z" }
}

Field	Type	Description
_metadata.success	boolean	true when the function executed without errors
_metadata.functionId	string	ID of the executed function
result	object	Function-specific result data (see below)
_metadata.durationMs	number	Execution time in milliseconds
_metadata.timestamp	string	ISO 8601 / RFC 3339 UTC timestamp

Function-Specific Output Data

Read Data Block Multi (s7.read.db.multi) — the node's result:

{
  "dbNumber": 100,
  "dataPoints": {
    "Temperature": {
      "value": 25.5,
      "dataType": "REAL",
      "start": 0,
      "size": 4,
      "rawBuffer": [...]
    },
    "Pressure": {
      "value": 1234,
      "dataType": "INT",
      "start": 4,
      "size": 2,
      "rawBuffer": [...]
    }
  },
  "readOperations": [
    { "start": 0, "size": 6, "bytesRead": 6 }
  ],
  "totalDataPoints": 2,
  "totalReads": 1
}

Field	Type	Description
result.dbNumber	number	Data block number that was read
result.dataPoints	object	Map of data point name to result. Each entry contains value, dataType, start, size, rawBuffer and quality (good — a point that decoded is the PLC's own reading; a read or parse failure fails the whole node instead of storing a value). Pass quality to a UNS Publish node's Quality parameter.
result.readOperations	array	Optimized read operations performed (adjacent points are coalesced)
result.totalDataPoints	number	Number of data points returned
result.totalReads	number	Number of actual read operations (may be fewer than data points due to coalescing)

Read Memory Area Multi (s7.read.memory.multi) — the node's result:

{
  "area": "M",
  "dataPoints": {
    "Flag1": {
      "value": true,
      "dataType": "BIT",
      "start": 0,
      "size": 1,
      "rawBuffer": [...]
    }
  },
  "readOperations": [
    { "start": 0, "size": 1, "bytesRead": 1 }
  ],
  "totalDataPoints": 1,
  "totalReads": 1
}

Field	Type	Description
result.area	string	Memory area: M (Merkers), I (Process Inputs), Q (Process Outputs)
result.dataPoints	object	Same structure as Read Data Block
result.readOperations	array	Optimized read operations
result.totalDataPoints	number	Number of data points
result.totalReads	number	Actual read operations performed

Function parameters for Read Data Block Multi:

Parameter	Type	Required	Description
dbNumber	Number	Yes	Data block number (0–65535)
dataPoints	Array	Yes	Data points to read (see Data Point Structure below)

Function parameters for Read Memory Area Multi:

Parameter	Type	Required	Description
area	String	Yes	Memory area: M, I, or Q
dataPoints	Array	Yes	Data points to read (see Data Point Structure below)

Data Point Structure:

Field	Type	Required	Description
name	String	Yes	Unique name for this data point
start	Number	Yes	Byte offset (>= 0)
size	Number	Yes	Size in bytes (1–65536)
dataType	String	Yes	S7 data type (see Supported Data Types)
bitPos	Number	For BIT only	Bit position (0–7), required when dataType is BIT

Read Coalescing

Adjacent data points are automatically merged into fewer read operations. Data points within 32 bytes of each other are combined into a single read (up to 255 bytes per operation), reducing PLC communication overhead.

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S7 Write Node

S7 Write Node

Write deterministic control values to Siemens PLC data blocks or memory areas.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Write Data Block (s7.write.db)	Write a value to a DB location	Download production orders or recipes
Write Memory Area (s7.write.memory)	Write a value to M or Q areas	Force outputs, toggle sequences, command transitions

Node Configuration

Parameter	Type	Required	Description
Connection	Selection	Yes	S7 connection profile to use
Function	Selection	Yes	Write function from the selected connection
Function Parameters	Dynamic	Varies	Auto-populated from the function schema. See your S7 connection functions for full parameter details.
Timeout Override	Number (seconds)	No	Override the default function timeout

All function parameters support expression syntax ({{ expression }}) and template placeholders (((paramName))) for dynamic values.

Input

The node receives the output of the previous node as input. Use expressions like {{ $input[0].result.value }} to pass dynamic values to write parameters.

Function-Specific Parameters and Output

Write Data Block (s7.write.db):

Parameter	Type	Required	Description
dbNumber	Number	Yes	Data block number (0–65535)
start	Number	Yes	Byte offset (>= 0)
dataType	String	Yes	S7 data type (see Supported Data Types)
value	String	Yes	Value to write (parsed according to dataType)
bitPos	Number	For BIT only	Bit position (0–7)
size	Number	For STRING/CHAR	Size in bytes (1–65536)

The node's result (result.dbNumber, result.start, result.dataType, result.value, result.bytesWritten; when the write ran is _metadata.timestamp):

{
  "dbNumber": 100,
  "start": 0,
  "dataType": "REAL",
  "value": "25.5",
  "bytesWritten": 4
}

Write Memory Area (s7.write.memory):

Parameter	Type	Required	Description
area	String	Yes	Memory area: M or Q only (I is read-only)
start	Number	Yes	Byte offset (>= 0)
dataType	String	Yes	S7 data type (STRING not supported for memory writes)
value	String	Yes	Value to write
bitPos	Number	For BIT only	Bit position (0–7)

The node's result (result.area instead of result.dbNumber, the rest as above):

{
  "area": "M",
  "start": 0,
  "dataType": "BIT",
  "value": "true",
  "bytesWritten": 1
}

BIT Writes

BIT writes use a Read-Modify-Write pattern: the node reads the current byte, modifies the specific bit, and writes the byte back. This ensures other bits in the same byte are preserved.

Safety First

Always implement validation and safety checks before writing to industrial equipment. Consider adding condition nodes to verify values are within safe ranges. The Input area (I) is read-only and cannot be written.

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S7 Read Group Node

The S7 Read Group node executes multiple S7 read operations in a single node with request coalescing for efficiency. It supports selective function lists, an All Functions mode, and parallel or sequential execution.

Node Configuration

Parameter	Type	Required	Default	Description
Connection	Selection	Yes	—	S7 connection profile
Function Selection	Selection	No	Select Functions	Select Functions reads the functions you list. All Functions reads every read function on the connection. By Labels reads every function whose labels match the labels you pick.
Functions	Array of {functionId, alias}	When Function Selection is Select Functions	[]	List of specific functions to execute. Each entry requires a functionId; alias is optional.
Execution Mode	Selection	No	parallel	parallel — all functions run concurrently. sequential — functions run one after another.
Continue on Error	Toggle	No	true	When enabled, the node continues executing remaining functions even if one fails
Debug Mode	Toggle	No	false	Enable detailed logging for troubleshooting

All Functions Mode

When Function Selection is All Functions, the function list is ignored. The node automatically discovers and executes every read function defined on the selected connection.

Read function types that All Functions runs:

Function Type	Description
s7.read.db.multi	Read Data Block Multi
s7.read.memory.multi	Read Memory Area Multi

Input

The node receives the output of the previous node as input.

Output Structure

The node output is the canonical {result, _metadata} envelope: result holds one entry per function read, keyed by the function's output key; _metadata holds the group's accounting.

{
  "result": {
    "DB100 Temperatures": {
      "value": { "dbNumber": 100, "dataPoints": { "Temperature": { "value": 25.5, "dataType": "REAL", "start": 0, "size": 4 } }, "totalDataPoints": 1, "totalReads": 1 },
      "success": true,
      "error": "",
      "duration": 45,
      "timestamp": "2026-09-07T08:30:00Z"
    },
    "Merker Flags": {
      "value": { "area": "M", "dataPoints": { "RunFlag": { "value": true, "dataType": "BIT", "start": 0, "size": 1 } }, "totalDataPoints": 1, "totalReads": 1 },
      "success": true,
      "error": "",
      "duration": 38,
      "timestamp": "2026-09-07T08:30:00Z"
    }
  },
  "_metadata": {
    "connectionId": "conn-123",
    "connectionName": "S7-1500 Line A",
    "total": 2,
    "successful": 2,
    "failed": 0,
    "totalDuration": 83,
    "executionMode": "parallel",
    "originalRequests": 2
  }
}

Each entry under result is one function's read — keyed by the function's alias, else its name, else its id (see Output Key Resolution):

Field	Type	Description
result.<alias>.value	any	What the function read — its own result.value when it has one (the whole {dbNumber, dataPoints, totalDataPoints, totalReads} object for a DB read, {area, dataPoints, …} for a memory read — neither result carries a top-level value), otherwise its whole result. null when the read failed
result.<alias>.success	boolean	true when this function's read succeeded
result.<alias>.error	string	Why the read failed; empty when it succeeded — always present
result.<alias>.duration	number	How long this function's read took, in milliseconds
result.<alias>.timestamp	string	When the read was issued, RFC 3339 UTC

The _metadata object is the group's execution summary:

Field	Type	Description
_metadata.connectionId	string	The connection every function was read on
_metadata.connectionName	string	That connection's display name
_metadata.total	number	How many functions the group ran
_metadata.successful	number	How many read successfully — including the ones onChange then suppressed
_metadata.failed	number	How many failed; successful + failed = total
_metadata.totalDuration	number	Wall-clock time of the whole group, in milliseconds
_metadata.executionMode	string	parallel or sequential
_metadata.originalRequests	number	How many functions were selected to run
_metadata.keyCollisions	string[]	Output keys that two or more functions resolved to — the later read overwrote the earlier under that key. Present only when it happened
_metadata.configWarnings	string[]	Non-fatal problems in the node's config, each saying what was ignored. Present only when there were any
_metadata.outputMode	string	onChange — present only in that mode
_metadata.suppressedCount	number	onChange mode: how many successful reads were unchanged since the last run and left out of result
_metadata.emittedCount	number	onChange mode: how many entries result carries — total − suppressedCount
_metadata.suppressedKeys	string[]	onChange mode: the output keys left out as unchanged. Present only when at least one was
_metadata.reason	string	onChange mode, when every successful read was unchanged: why result is empty — the node buffers instead of waking downstream

Output Key Resolution

Each function result is keyed in the output map using the first available value:

1. Alias — the custom alias set in the function entry
2. Function Name — the name defined on the connection function
3. Function ID — the unique function identifier (fallback)

Execution Modes

Parallel (default)

• All functions execute concurrently.
• Fastest total execution time.
• Best when reading from different data blocks or memory areas.

Sequential

• Functions execute one after another in list order.
• More predictable timing and lower peak load on the PLC.
• When Continue on Error is off, execution stops at the first failure.

tip

S7 PLCs typically support a limited number of concurrent connections (usually 8). Parallel mode runs multiple reads within a single connection, which is safe and efficient.

Error Handling

Continue on Error	Behavior
true (default)	The node completes even if individual functions fail. Failed functions include an error field in their result. The node output remains successful.
false	The node fails as soon as any function fails. In sequential mode, remaining functions are skipped. The node result is marked as failed.

Validation Rules

• connectionId is required.
• executionMode must be parallel or sequential.
• With Select Functions, at least one function entry is required; with By Labels, at least one label is required.
• Duplicate functionId values are not allowed.
• Duplicate alias values are not allowed.
• The connection type must be s7.

Best Practices

• Use All Functions for complete PLC data snapshots during commissioning or diagnostics.
• Use specific functions in production pipelines for targeted reads.
• Assign aliases to make output keys descriptive (e.g., "Line A Temperatures" instead of a function ID).
• Leverage read coalescing — define data points close together in the same DB to minimize the number of actual read operations.

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Supported Data Types

The following data types are supported in S7 read and write operations:

Data Type	Size	Description
BIT	1 byte	Boolean value (requires bitPos 0–7)
BYTE	1 byte	Unsigned 8-bit integer (0–255)
WORD	2 bytes	Unsigned 16-bit integer (0–65535)
DWORD	4 bytes	Unsigned 32-bit integer
INT	2 bytes	Signed 16-bit integer (−32768 to 32767)
DINT	4 bytes	Signed 32-bit integer
REAL	4 bytes	32-bit IEEE 754 floating point
LREAL	8 bytes	64-bit IEEE 754 floating point
CHAR	Variable	ASCII character(s)
STRING	Variable	S7 string with 2-byte header (DB writes only)

Memory Areas:

Area	Name	Readable	Writable
M	Merkers (Flags)	Yes	Yes
I	Process Inputs	Yes	No
Q	Process Outputs	Yes	Yes

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Settings Tab

All S7 node types share the same Settings tab:

Setting	Type	Default	Description
Description	Text	—	Optional description displayed on the node
Timeout (seconds)	Number	Pipeline default	Maximum time the node may run before timing out
Retry on Timeout	Toggle	Pipeline default	Automatically retry the node if it times out
Retry on Fail	Toggle	Pipeline default	Automatically retry the node if it fails
On Error	Selection	Pipeline default	Error strategy: Pipeline Default (the pipeline's Error Handling setting), Stop Pipeline or Continue Execution

When left at their defaults, these settings inherit from the pipeline-level execution configuration.