S7-300 to S7-300 Communication Setup with TIA Portal V13 SP1

Overview: Bridging Independent S7-300 Machines with a Link PLC

Brownfield factory cells based on SIMATIC S7-300 controllers typically evolve without a unified network plan. When a new machine is added that must exchange a defined I/O dataset with five pre-existing cells, pulling dedicated PROFIBUS cable runs is rarely practical. The field-proven alternative is to install a link PLC that sits on the same Industrial Ethernet subnet as the existing cells, and exposes a PROFIBUS segment terminated by DP/DP couplers to the new vendor machine.

This reference covers the full engineering of that bridge using TIA Portal V13 SP1, including:

• Hardware selection between CP 343-1 Lean and a CPU 315-2 PN/DP as the link controller.
• Why the CP 343-1 Lean is restricted to server role in S7 connections.
• How to keep alterations to the existing cell programs to a minimum.
• Configuring S7 connections with PUT/GET in TIA Portal V13 SP1.
• Integrating DP/DP couplers (Siemens 6ES7158-0AD01-0XA0) on the new machine's PROFIBUS.
• Commissioning, diagnostics, and verification steps.

Prerequisites

Hardware Selection: Why CPU 315-2 PN/DP Beats CP 343-1 Lean as a Link

The original concept was to drop a CPU 315-2 DP with a CP 343-1 Lean into the new machine. The architecture is physically possible, but the CP 343-1 Lean has a hard functional restriction that determines where it can sit in the topology:

Because the link PLC must read signals from five partner cells and write consolidated tags to the DP/DP couplers, the link must be able to initiate PUT/GET transfers. A partner that holds a CP 343-1 Lean can only answer incoming requests, not start them. With one CP 343-1 Lean there is no way to drive the data exchange on its own.

Network Topology

The link PLC is on the same Ethernet subnet as the four partner cells. Its PROFIBUS DP master port daisy-chains the four DP/DP couplers inside the new vendor machine. Each coupler passes a pre-defined slice of process data between the link PLC's PROFIBUS image and the new machine's own PROFIBUS master.

Step-by-Step: Configuring the Link PLC in TIA Portal V13 SP1

Step 1 - Create the project and add the link PLC

1. Open TIA Portal V13 SP1 and select Create new project.
2. In the project tree, choose Add new device > SIMATIC S7-300 > CPU > CPU 315-2 PN/DP > 6ES7315-2EH14-0AB0 V3.3.
3. Open Device view and confirm the integrated PROFINET interface and PROFIBUS DP master appear in slot 2 (PN) and slot 2 (X2 DP).

Step 2 - Configure the PROFINET interface

1. Select the PN interface and assign IP 10.10.0.10, subnet mask 255.255.0.0.
2. Add the partner CPUs as Unspecified CPU 300 in Devices & Networks > Network view. Enter each partner's IP (10.10.0.11 through 10.10.0.14) under PROFINET interface > Ethernet addresses.
3. Create a logical S7 connection from the link PLC to each partner. The endpoint on the partner side is left as unspecified; the partner IP is entered manually.

Step 3 - Configure the S7 connection properties

For each of the four S7 connections, set the following parameters in Properties > General > Connection mechanisms:

Step 4 - Enable PUT/GET access on the partner S7-300 CPUs

On every partner CPU that exposes its data, the PUT/GET access flag must be enabled. This is a CPU property in STEP 7 / TIA Portal:

1. Open the partner's project (or online configuration if the original project is unavailable).
2. Select the CPU and go to Properties > Protection & Security > Connection mechanisms.
3. Tick Permit access with PUT/GET communication from remote partner.
4. Compile and download to the partner CPU.

Step 5 - Program PUT/GET in the link PLC

Use the PUT and GET instructions from the Instructions > Communication > S7 Communication task card. The block interface for the link PLC program is:

// Data block DB100 - shared with vendor machine via PROFIBUS
DATA_BLOCK "DB_Vendor_Image"
  STRUCT
    From_CellA : WORD;     // status word from Cell A
    From_CellB : WORD;     // status word from Cell B
    From_CellC : WORD;     // status word from Cell C
    From_CellD : WORD;     // status word from Cell D
    To_All     : WORD;      // consolidated command broadcast
  END_STRUCT
END_DATA_BLOCK

OB1 cyclic call (SCL example):

// Read from Cell A (partner IP 10.10.0.11, connection ID 1)
"GET_DB".ID        := 1;                     // connection ID
"GET_DB".REQ       := %DB5.DBX0.0;           // 1 Hz trigger from cyclic OB
"GET_DB".DONE      := "CellA_Done";
"GET_DB".ERROR     := "CellA_Err";
"GET_DB".STATUS    := "CellA_Status";
"GET_DB".ADDR_1    := P#DB10.DBX0.0 BYTE 2;  // partner DB10, 2 bytes
"GET_DB".RD_1      := P#DB100.DBX0.0 BYTE 2; // local target

// Write to Cell A
"PUT_DB".ID        := 1;
"PUT_DB".REQ       := %DB5.DBX0.1;
"PUT_DB".ADDR_1    := P#DB11.DBX0.0 BYTE 2;
"PUT_DB".SD_1      := P#DB100.DBX10.0 BYTE 2;

Each GET/PUT call is fired once per cycle on a 100 ms tick from OB35 to avoid flooding the partner CPUs.

Step-by-Step: Integrating the DP/DP Couplers

1. In the link PLC's device configuration, open the PROFIBUS subnet and set master address to 2 with transmission rate 1.5 Mbps.
2. From the hardware catalog, drag the DP/DP coupler (6ES7158-0AD01-0XA0) four times onto the PROFIBUS subnet and assign PROFIBUS addresses 3, 4, 5, 6.
3. For each coupler, open the device properties and define the I/O length on the link side (e.g. 4 words in / 4 words out per coupler). The vendor must mirror the same length on the opposite side.
4. Add a global data block (DB200) on the link PLC with one slice per coupler, mapped symbolically to the vendor's image.

DP/DP coupler addressing table

Connection Resource Accounting

Both the link PLC's CPU and the partner CP/CPU modules have a hard limit on concurrent S7 connections. Crossing the limit raises SF on the partner and the connection is silently rejected.

Commissioning Sequence

1. Download the link PLC's hardware configuration. Verify the partner CPUs are reachable from Online & Diagnostics > Accessible nodes.
2. Enable PUT/GET on each partner and recompile / download (or use online configuration if the project is not available).
3. Download the link PLC's S7 program with PUT/GET blocks.
4. Watch the STATUS output of each GET block. A status of 0000_0000 indicates success; common transient codes are 0001_0001 (job active) and 0001_0081 (partner rejected - check PUT/GET flag).
5. Once the Ethernet side is stable, download the PROFIBUS configuration and verify the DP/DP couplers show green RUN on the diagnostic LEDs.
6. Force one bit in DB100 from the link PLC and verify it appears in the vendor's input image, then verify a return bit in the opposite direction.

Diagnostics and Verification Matrix

Programming in SIMATIC Manager vs TIA Portal V13 SP1

Functionally, both STEP 7 V5.5 (SIMATIC Manager) and TIA Portal V13 SP1 generate the same S7 connection configuration. The differences relevant to this scenario are:

If the existing cell projects are still in SIMATIC Manager and not migrated, it is possible to use TIA Portal V13 SP1 only for the link PLC and import the partner projects via Migration > Migrate project to step through the protection settings. Migrating is not strictly required; PUT/GET will work as long as the partner CPU has the runtime flag set in its loaded configuration, regardless of the engineering tool used to write that configuration.

Spare-Parts and Lifecycle Notes

• CPU 315-2 PN/DP 6ES7315-2EH14-0AB0: shipped with firmware V3.3; remains in active sales per the Siemens product portfolio.
• CP 343-1 Lean 6GK7343-1CX10-0XE0: phased out of catalog; replacements are the SCALANCE M series or a PROFINET interface on the CPU itself.
• DP/DP coupler 6ES7158-0AD01-0XA0: still orderable, no functional successor required.
• Always update to the latest hotfix of TIA Portal V13 SP1 (Update 9 at time of writing) before commissioning to avoid the PUT/GET status code display bug reported in early service packs.

Verification Checklist Before Hand-Over

1. All four partner connections show STATUS = 0 for at least 10 minutes of OB35 cycles.
2. Forced bits in the link PLC appear in the vendor machine's HMI within one PROFIBUS cycle (≤ 10 ms at 1.5 Mbps).
3. Loss of one partner's Ethernet cable is detected by the link PLC (STATUS jumps to a non-zero value) and a vendor-side alarm is raised.
4. Diagnostic buffer of the link PLC contains no SF events during a 1-hour soak test.
5. Connection resource utilization on every partner is recorded in the hand-over document.

FAQ