The Siemens S7 Plus Connector reads and writes symbolic variables in Siemens S7-1200 and S7-1500 PLCs. Use it for optimized data blocks, symbolic tag paths, arrays, user-defined types, and direct input, output, or marker access.

This guide explains instance configuration, item discovery, symbolic and direct addressing, supported data types, array and UDT handling, and troubleshooting.

Prerequisites

• Install the Siemens S7 Plus Connector.
• Use a Siemens S7-1200 or S7-1500 PLC that supports S7CommPlus communication.
• Connect SIA Connect and the PLC to networks where they can reach each other.
• Allow ISO-on-TCP communication on TCP port 102.
• Download the current PLC program and place the PLC in the required operating state.
• Configure PLC users, passwords, and access rights when authentication is enabled.
• Identify the exact symbolic paths and data types when creating items manually.

Configure a Siemens S7 Plus instance

1. Open Workspace > Instances.
2. Create an instance and select the Siemens S7 Plus Connector.
3. Enter a clear instance name.
4. Enter the PLC IP address or hostname in Address.
5. Enter the PLC Username and Password when authentication is required.
6. Set the connection Timeout.
7. Create the instance.

The Connector communicates on TCP port 102. The port cannot be changed in the instance parameters.

Instance parameters

The Connector attempts a secure S7CommPlus connection first. It can automatically try a compatible legacy S7CommPlus connection when the PLC rejects TLS initialization.

Discover items

The Siemens S7 Plus Connector supports item discovery on an existing instance. It does not support instance discovery.

1. Open the Siemens S7 Plus instance.
2. Start item discovery.
3. Wait while the Connector connects to the PLC and browses its symbols.
4. Review the discovered candidates and warnings.
5. Select the required candidates.
6. Import the selected items.

Discovery uses the instance Address, Username, Password, and Timeout. It imports supported scalar leaf symbols and assigns their detected data types.

Discovery does not import complete array roots or complete STRUCT and UDT roots. Supported scalar members inside structures can appear as individual candidates. Unsupported data types are skipped and reported in the discovery warnings.

Discovered items are configured for read and write access. Confirm the PLC permissions and the intended item direction before using a discovered item as a mapping receiver.

Configure an item manually

1. Open the Siemens S7 Plus instance.
2. Create an item.
3. Enter a clear item name.
4. Enter the PLC tag path or direct memory address in Symbol.
5. Select the matching Type.
6. Configure the item's access and polling settings as required.
7. Create the item.

The selected Type must match the PLC variable or array element type. A mismatch can cause incorrect values, failed writes, or skipped operations.

Item parameters

Address symbolic variables

Use the data block and variable names exactly as defined in TIA Portal.

Quoted and unquoted names are accepted. For example, "DB_Arrays"."IntArray" and DB_Arrays.IntArray refer to the same symbolic path.

Use direct input, output, and marker addresses

• An optional percent prefix is accepted. For example, %MW10 is treated as MW10.
• I0, Q0, and M0 use byte access when no size letter or bit number is provided.
• Analog forms such as AIW0 and AQW0 are not supported.
• PLC input memory is normally read-only. The PLC will usually reject writes to an I address.

Supported data types

For BOOL writes, 0 and false are written as false. 1 and true are written as true. Any other non-empty value is also treated as true.

Read and write arrays

Read a complete array

Use the array root symbol without an index. The value is returned as a compact JSON array.

Example: DB_Arrays.IntArray can return [0,1,2,3,4].

BOOL arrays are returned as numeric values, such as [1,0,1,0].

Read or write one element

Add the PLC array index to the symbol. For example, DB_Arrays.IntArray[4] reads or writes only element 4.

The Connector respects arrays whose lower bound is not zero. An array declared as Array[1..10] accepts indexes from 1 to 10.

Write a complete array

Use the array root symbol and write a valid JSON array, such as [10,20,30,40]. The Connector expands the value into indexed writes starting from the PLC array's lower bound.

• The JSON array must contain at least one element.
• The number of supplied elements cannot exceed the PLC array length.
• The configured Type must match the PLC array element type.
• Full and indexed writes to STRING and WSTRING arrays are not supported.
• Indexed writes to multidimensional arrays are not supported.

Read and write UDTs and structures

Complete UDT writes support primitive scalar fields and primitive arrays. Missing or unknown JSON fields are ignored, which allows partial object updates. For example, {"Setpoint":33} updates only the matching Setpoint field.

BOOL fields in returned UDT JSON use 0 and 1.

Writing a complete element of a UDT array is not supported. Writing an indexed array member inside a UDT array element, such as DB_Process.Motors[2].Values[1], is also not supported.

Verify communication

1. Enable the Siemens S7 Plus instance and its items.
2. Confirm that the instance has no connection or authentication error.
3. Confirm that scalar item values match the corresponding PLC variables.
4. Check array and UDT values for valid JSON formatting.
5. For a writable variable, perform a controlled write only when it is safe.
6. Confirm the value in TIA Portal and verify that the item reads back the expected result.

Troubleshoot the Siemens S7 Plus Connector

Related articles

• Install and manage Connectors
• Create and edit instances
• Create and edit items
• Discover instances and items
• Ping tool
• Troubleshoot Connector, instance, item, and mapping errors
• Configure the Siemens S7 Connector
• Send Siemens S7 Plus data to an MQTT broker
• Siemens S7 Plus releases