Siemens S7 Write

This function block is used to send values into a Siemens S7 PLC (DB area). It lets you pick the DB number, byte address, data type and optionally a bit position for boolean writes. You can choose immediate (synchronous) writes or background (asynchronous) writes and provide an optional value to be sent when the scenario stops.

📥 Inputs

Enable Boolean input that enables the block. When False, the block will not send data.

Data Generic input containing the value to write to the PLC (number, boolean, text, depending on the selected data type).

[Optional] Data on Stop Generic input to provide a value that will be written when the block stops or the scenario finishes.

S7 Client Generic input that accepts a PLC connection reference (use with Siemens S7 Connect or a shared client provider).

📤 Outputs

This block does not produce outputs.

🕹️ Controls

DB Number DB number in the PLC where data will be written.

DB Byte Address Byte offset inside the DB where the write will start.

Bit Position Bit index inside the target byte (used only for boolean writes).

DB Data Type Dropdown to select the data type to write (examples: Boolean, Int, DInt, Real, String, Time, ...).

Connection Type Dropdown to choose between Async and Sync write modes.

🎯 Key Features

• Background writing option: choose Async to queue writes and run them in the background for better throughput.

• Immediate writes: choose Sync to write immediately (recommended when multiple blocks write to the same bytes).

• Wide data type support: supports numeric types, strings, boolean writes (with bit selection), and time types.

• Optional stop-time write: specify a separate value to be written when the block is stopped or removed.

• Automatic client reconnection guidance: the block can be paired with a connection provider to manage PLC connections.

⚙️ Running mechanism (user-facing)

• Provide a valid S7 Client from a connection block such as Siemens S7 Connect.

• Send values into Data while Enable is True to perform writes.

• If Connection Type is set to Async, writes are queued and executed on a background worker so the rest of the flow continues without waiting.

• If Connection Type is set to Sync, writes happen immediately and the block waits until the write finishes. This is safer when multiple writers target the same bytes.

• If you provide [Optional] Data on Stop, that value will be written when the block is stopped or removed.

📝 How to use (simple)

1. Add a connection provider block like Siemens S7 Connect and connect its client output to S7 Client.

2. Enter the destination DB number in DB Number and the byte offset in DB Byte Address.

3. Select the correct DB Data Type for the value you intend to write. If writing a boolean, set Bit Position.

4. Provide the value to be written to the Data input (use Number Input, String Input or other producers).

5. Toggle Enable (or drive it with a trigger block such as Logic Input or Rising Edge) to perform the write.

6. Optionally set [Optional] Data on Stop if you need a final value to be written when stopping.

💡 Tips and Tricks

• For connection setup, pair with Siemens S7 Connect so the connection is shared and managed separately.

• Use Siemens S7 Read after this block to verify the written value (read-then-compare).

• Use Logic Input or Rising Edge to trigger single-shot writes when an event occurs instead of continuous writes.

• Use Number Input or String Input blocks to feed clean, user-editable values into Data.

• Choose Sync when multiple blocks may write to overlapping DB addresses to avoid conflicting updates. Use Async for higher throughput when writes target different areas.

• Combine with Data Memory to hold a value and only send when it changes (prevents unnecessary writes).

• Add a Debug Input or connect a logger (CSV Export or Image Logger where appropriate) to keep a write history for troubleshooting.

• If you want to publish write events externally, route the same value to MQTT Publish or REST API - Post blocks after a successful write.

🛠️ Troubleshooting

• No connection / write fails: check that a valid S7 Client is connected (use Siemens S7 Connect).

• Wrong data type: ensure the selected DB Data Type matches the type of the Data you provide (e.g., do not feed text when a numeric type is selected).

• Boolean not changing: confirm the correct Bit Position is set and that the DB byte address is correct.

• Conflicting writes: if multiple blocks write to the same byte(s) and results are inconsistent, switch to Sync or consolidate writes into a single block.

• Need a guaranteed final write: provide the final value to [Optional] Data on Stop so it will be written when the block is removed or the scenario stops.

If you need example combinations, try: Number Input → Data and Logic Input → Enable for manual writes, or Siemens S7 Read → verify written values after using this block.