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:

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

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

Function-Specific Output Data

Read Data Block Multi (s7.read.db.multi):

{
  "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
dbNumber	number	Data block number that was read
dataPoints	object	Map of data point name to result. Each entry contains value, dataType, start, size, and rawBuffer.
readOperations	array	Optimized read operations performed (adjacent points are coalesced)
totalDataPoints	number	Number of data points returned
totalReads	number	Number of actual read operations (may be fewer than data points due to coalescing)

Read Memory Area Multi (s7.read.memory.multi):

{
  "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
area	string	Memory area: M (Merkers), I (Process Inputs), Q (Process Outputs)
dataPoints	object	Same structure as Read Data Block
readOperations	array	Optimized read operations
totalDataPoints	number	Number of data points
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.payload.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)

Output:

{
  "dbNumber": 100,
  "start": 0,
  "dataType": "REAL",
  "value": "25.5",
  "bytesWritten": 4,
  "timestamp": "2026-01-15T08:30:00Z"
}

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)

Output:

{
  "area": "M",
  "start": 0,
  "dataType": "BIT",
  "value": "true",
  "bytesWritten": 1,
  "timestamp": "2026-01-15T08:30:00Z"
}

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, a Read All mode, and parallel or sequential execution.

Node Configuration

Parameter	Type	Required	Default	Description
Connection	Selection	Yes	—	S7 connection profile
Read All	Toggle	No	false	When enabled, executes all read functions from the connection
Functions	Array of {functionId, alias}	When Read All is off	[]	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

Read All Mode

When Read All is enabled the function list is ignored. The node automatically discovers and executes every read function defined on the selected connection.

Supported read function types for Read All:

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

{
  "DB100 Temperatures": {
    "value": {
      "dbNumber": 100,
      "dataPoints": {
        "Temperature": { "value": 25.5, "dataType": "REAL", "start": 0, "size": 4 }
      },
      "totalDataPoints": 1,
      "totalReads": 1
    },
    "success": true,
    "duration": 45,
    "timestamp": "2026-01-15T08:30:00Z"
  },
  "Merker Flags": {
    "value": {
      "area": "M",
      "dataPoints": {
        "RunFlag": { "value": true, "dataType": "BIT", "start": 0, "size": 1 }
      },
      "totalDataPoints": 1,
      "totalReads": 1
    },
    "success": true,
    "duration": 38,
    "timestamp": "2026-01-15T08:30:00Z"
  },
  "_meta": {
    "connectionId": "conn-789",
    "connectionName": "S7-1500 Line A",
    "total": 2,
    "successful": 2,
    "failed": 0,
    "totalDuration": 83,
    "executionMode": "parallel",
    "originalRequests": 2
  }
}

Each function result contains:

Field	Type	Description
value	any	The function's return data (Read DB or Read Memory result)
success	boolean	Whether this function succeeded
error	string	Error message (present only on failure)
duration	number	Execution time in milliseconds
timestamp	string	ISO 8601 / RFC 3339 UTC timestamp

The _meta object provides execution summary:

Field	Type	Description
connectionId	string	Connection profile ID
connectionName	string	Connection profile display name
total	number	Total functions executed
successful	number	Count of successful executions
failed	number	Count of failed executions
totalDuration	number	Wall-clock time for the entire group (ms)
executionMode	string	parallel or sequential
originalRequests	number	Number of function configs submitted
keyCollisions	string[]	Output keys that appeared more than once (omitted when empty)

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.
• When Read All is off, at least one function entry is required.
• Duplicate functionId values are not allowed.
• Duplicate alias values are not allowed.
• The connection type must be s7.

Best Practices

• Use Read All 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: stop the pipeline, continue to the next node, or follow the error output path

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