Configuring CP 343-1 PROFINET IO in STEP 7 with FC11/FC12

CP 343-1 Family Overview

The CP 343-1 family of communications processors plugs into the S7-300 backplane and provides an Industrial Ethernet / PROFINET interface on top of the CPU's integrated port or as a stand-alone interface. Each variant differs in PROFINET capability (IO Controller, IO Device, CBA), number of ports, supported firmware features, and supported protocols (S7 communication, TCP/UDP, ISO-on-TCP, PROFINET, OPC UA on Advanced variants).

The field report explicitly addresses the CP 343-1 Lean (6GK7343-1CX10-0XE0), the most recent Lean variant at the time, which supports PROFINET IO Device operation but cannot function as a PROFINET IO Controller. For PROFINET IO Controller functionality, a non-Lean CP 343-1 or higher variant is required.

According to Siemens support entry 109820745 – CP 343-1 as PROFINET IO controller in STEP 7 Professional, when an Industrial Ethernet CP of the S7-300 is operated as a PROFINET IO Controller or IO Device, the FC11 (PNIO_SEND) and FC12 (PNIO_RECV) function blocks from the SIMATIC NET CP 300 library must be called in the S7 program.

Variant Capability Summary

PROFINET Architecture Background

PROFINET is an Industrial Ethernet-based protocol standardized by PROFIBUS & PROFINET International (PI). It uses the following roles:

• IO Controller: The PLC that runs the PROFINET stack and exchanges cyclic I/O with one or more IO Devices.
• IO Device: A distributed field device (or another PLC's CP) that is assigned to an IO Controller and provides cyclic input/output data.
• IO Supervisor: A diagnostic or engineering station (e.g., STEP 7, TIA Portal) used for commissioning and diagnostics — does not participate in cyclic data exchange.

The CP 343-1 supports IO Controller and IO Device roles depending on variant. PROFINET exchanges data cyclically using Record Data CRs (Communication Relations) for IOCR (IO Communication Relationship) and acyclic Record Data for parameters, diagnostics, and identification.

IRT (Isochronous Real-Time) is a synchronised, scheduled PROFINET class used for high-deterministic motion applications. The CP 343-1 Lean does not support IRT; only the Advanced and ERPC variants support it on S7-300.

CP 343-1 Variant Selection Decision Matrix

Apply the following decision path before procurement and configuration:

1. Does the S7-300 need to operate as a PROFINET IO Controller?
   • Yes → CP 343-1 (standard), CP 343-1 Advanced, or CP 343-1 ERPC required.
   • No → CP 343-1 Lean (6GK7343-1CX10-0XE0) is sufficient if only IO Device functionality is needed.
2. Is PROFINET CBA (Component Based Automation) needed?
   • Yes → CP 343-1 Advanced required.
   • No → Any variant except Lean (for IO Controller).
3. Is IRT (Isochronous Real Time) required for motion or high-deterministic applications?
   • Yes → CP 343-1 Advanced or CP 343-1 ERPC with matching firmware.
   • No → Any PROFINET-capable variant.
4. Is S7 communication (PUT/GET) needed in parallel with PROFINET?
   • Yes → All variants support S7 communication alongside PROFINET.
5. Is OPC UA, IT integration, or web server needed?
   • Yes → CP 343-1 Advanced.

Prerequisites

Hardware

• S7-300 station with CPU 3xx (e.g., CPU 315-2 PN/DP, CPU 317-2 PN/DP, CPU 319-3 PN/DP). The CPU is required for cyclic OB1 execution even when the CP handles PROFINET.
• CP 343-1 variant appropriate for the role. For IO Device only: 6GK7343-1CX10-0XE0.
• PROFINET-capable partner device (IO Device, IO Controller, or another CP 343-1).
• Industrial Ethernet cabling — CAT5e minimum, RJ45 or M12 D-coded per device. Maximum segment length 100 m (copper).
• For initial commissioning: PG/PC with Ethernet interface.

Software

• STEP 7 V5.5 SP4 or later (the source explicitly references STEP 7 with the NCM S7 Manual installed).
• SIMATIC NET CD with the CP 300 library, which provides FC11/FC12 (PNIO_SEND/PNIO_RECV), and the FB55/FB56/FB65/FB66 transport blocks for TCP/UDP/ISO-on-TCP.
• NCM S7 Manual for SIMATIC NET CP 300 — installed via STEP 7 Setup under Documentation > Manuals > NCM S7.
• GSD file (GSDML-Vx.x-...) for any third-party IO Device, imported into HW Config under Options > Install GSD File.

Firmware

• Verify the CP's firmware version is compatible with your STEP 7 version. Open HW Config, right-click the CP, choose Object Properties > Diagnostics; the firmware version is reported under Module Identification. If the firmware is older than supported by STEP 7, an S7-Online firmware update may be required.

Hardware Installation Procedure

1. Power down the S7-300 station before inserting or removing the CP.
2. Plug the CP 343-1 into a free slot in the S7-300 rack. Slot rules:
   • Slot 0: reserved for the rack itself (in STEP 7).
   • Slot 1: Power Supply (PS).
   • Slot 2: CPU.
   • Slot 3: reserved for Interface Module (IM) in expansion racks.
   • Slot 4–11: Signal Modules, Function Modules, CPs (CP 343-1 typically occupies slot 4–11).
3. Tighten the front screws of the CP to seat it on the backplane. Improper seating produces "module fault" diagnostics.
4. Connect the PROFINET cable to port 1 (P1) of the integrated switch. Port 2 (P2) can be used for daisy-chaining additional PROFINET devices in a line topology.
5. Power up the S7-300 station. Verify the CP's LEDs indicate readiness: RUN green steady, STOP off, LINK green steady on the connected port.

STEP 7 Project Configuration – IO Controller Role

Inserting the CP in HW Config

1. Open SIMATIC Manager and load the S7-300 station.
2. Open HW Config for the station.
3. From the hardware catalog, navigate to SIMATIC 300 > CP 300 > Industrial Ethernet > CP 343-1.
4. Drag the correct order number (e.g., 6GK7 343-1EX30-0XE0 series for IO Controller) into a free slot (typically slot 4–11).
5. Double-click the CP to open Properties – CP 343-1.

Configuring the PROFINET Interface

1. In Properties, select the PROFINET tab or Ethernet Interface submenu.
2. Click Properties next to the PROFINET interface.
3. Assign an IP address, Subnet mask, and (optionally) a Router address for the CP.
4. Click New to create a PROFINET subnet (e.g., PN/IO_1) or select an existing one.
5. Confirm with OK.

Configuring the CP as PROFINET IO Controller

1. Right-click the CP 343-1 in HW Config and choose Insert PROFINET IO System.
2. The PROFINET IO System appears graphically under the CP.
3. From the hardware catalog, navigate to PROFINET IO > [Manufacturer] > [Device].
4. Drag the IO Device into the PROFINET IO System. Slots are populated automatically (Slot 0 = head module / interface; Slot 1+ = I/O modules).
5. Configure the IO Device's IP address and PROFINET device name. The device name is mandatory for PROFINET and must match the configuration loaded into the IO Device.
6. Click each slot of the IO Device to view and edit the I-addresses (inputs) and Q-addresses (outputs). These addresses are referenced in the S7 program as I/Q peripherals.

Assigning the Device Name to the Physical IO Device

1. In HW Config, right-click the PROFINET IO System and select Assign device name.
2. Select the accessible PROFINET nodes found via DCP discovery.
3. Assign the configured device name and click Assign name.
4. The IO Device reboots briefly to apply the name. Verify the LINK LED returns to steady green.

Downloading the Configuration

1. Save and compile HW Config (Station > Save and Compile).
2. Select the station and click Download to Target > Selected modules.
3. Confirm the download to both the CPU and the CP.

STEP 7 Project Configuration – IO Device Role (CP 343-1 Lean)

This section covers the CP 343-1 Lean (6GK7343-1CX10-0XE0) acting as a PROFINET IO Device, the case explicitly described in the field report.

Configure CP 343-1 Lean in HW Config

1. Open HW Config for the S7-300 station.
2. From the hardware catalog, navigate to SIMATIC 300 > CP 300 > Industrial Ethernet > CP 343-1 Lean and select 6GK7343-1CX10-0XE0.
3. Drag the CP into a free slot.
4. Double-click the CP and configure IP address, Subnet mask, and PROFINET subnet.
5. Apply and confirm.

Enable PROFINET IO Device Mode

1. Right-click the CP 343-1 Lean and select Properties > PROFINET Interface.
2. Enable PROFINET IO Device mode in the role selection.
3. Define the slots to expose to the IO Controller:
   • Slot 0: CP itself (diagnostics slot, mandatory).
   • Slot 1, 2, 3, …: PROFINET I/O modules (input, output, or mixed).
4. Configure each slot's address range (input/output bytes/words). Example:
   • Slot 1: 4 bytes input (IB 100–IB 103).
   • Slot 2: 4 bytes output (QB 100–QB 103).
5. Click New in Transfer areas to define data exchange with the IO Controller.
6. Set the Length of the transfer area in bytes and assign it to a slot.

Assign Device Name

The CP 343-1 Lean must receive a unique PROFINET device name. Use one of the following methods:

• SIMATIC Manager: PLC > Ethernet > Assign PROFINET Device Name.
• STEP 7 Online Interface: PG/PC reachable on the PROFINET subnet.
• From the IO Controller project: HW Config > IO System > Assign device name.

Download Configuration to S7-300

Download the HW Config to the CPU. The CP retains its PROFINET device name across power cycles in non-volatile storage.

FC11 PNIO_SEND Interface Reference

The FC11 (PNIO_SEND) block is part of the SIMATIC NET CP 300 library and ships with STEP 7. When the CP 343-1 operates as a PROFINET IO Controller, FC11 transmits output data to the configured IO Devices; when it operates as an IO Device, FC11 transmits the IO Device's process output data to the IO Controller.

FC11 Call Example – Structured Text

// OB1 - cyclic program
// Send process data to PROFINET IO Controller
PNIO_SEND(
  CPLADDR := W#16#0100,        // CP base address from HW Config
  SEND    := P#DB20.DBX0.0 BYTE 32,
  LEN     := 32,
  DONE    := M100.0,
  ERROR   := M100.1,
  STATUS  := MW102
);

FC11 Call Example – Ladder Logic

// Network 1 - PNIO_SEND call
A       M100.0            // DONE pulse
=       M200.0            // send_ok_flag

// FC11 instance call
CALL "PNIO_SEND"
  CPLADDR := W#16#0100
  SEND    := P#DB20.DBX0.0 BYTE 32
  LEN     := 32
  DONE    := M100.0
  ERROR   := M100.1
  STATUS  := MW102

FC12 PNIO_RECV Interface Reference

FC12 (PNIO_RECV) receives input data from the IO Controller (when CP is an IO Device) or from IO Devices (when CP is an IO Controller).

FC12 Call Example – Structured Text

PNIO_RECV(
  CPLADDR := W#16#0100,
  RECV    := P#DB30.DBX0.0 BYTE 32,
  LEN     := MW110,
  NDR     := M120.0,
  ERROR   := M120.1,
  STATUS  := MW122
);

Complete OB1 Program for CP 343-1 Lean as IO Device

// OB1 - Main cyclic
// Receive input data from IO Controller
PNIO_RECV(
  CPLADDR := W#16#0100,        // CP base address
  RECV    := P#DB40.DBX0.0 BYTE 32,
  LEN     := "recv_len",
  NDR     := "io_new_data",
  ERROR   := "io_recv_err",
  STATUS  := "io_recv_status"
);

// Process received data
IF "io_new_data" THEN
   // Example: copy input word 0 to flags
   "input_word_0" := DB40.DBW0;
   "process_enable" := TRUE;
END_IF;

// Application logic
IF "process_enable" AND NOT "emergency_stop" THEN
   DB41.DBW0 := DB40.DBW2;        // echo back modified data
END_IF;

// Transmit output data back to IO Controller
PNIO_SEND(
  CPLADDR := W#16#0100,
  SEND    := P#DB41.DBX0.0 BYTE 32,
  LEN     := 32,
  DONE    := "io_send_done",
  ERROR   := "io_send_err",
  STATUS  := "io_send_status"
);

Integrating the SIMATIC NET Library into the Project

If FC11/FC12 are not present in the S7 program, install them as follows:

1. Locate the SIMATIC NET CP 300 library. Default paths:
   • STEP 7 installation: C:\Programs\Siemens\Automation\S7libs\SIMATIC_NET_CP_300
   • SIMATIC NET CD: \CP_300\S7libs
2. Open SIMATIC Manager, choose File > Open > Library, browse to SIMATIC_NET_CP_300.
3. From the library's Blocks container, copy FC11 (PNIO_SEND) and FC12 (PNIO_RECV) into your S7 project's Blocks.
4. Alternative installation: Options > Install Library in SIMATIC Manager, then reference the library directly.

The NCM S7 Manual documents all function blocks of the SIMATIC NET CP 300 library. Install it via STEP 7 Setup under Documentation > Manuals > NCM S7.

Diagnostics and Online Tools

Online Diagnostics Path

• In HW Config, right-click the CP 343-1 → PLC > Module Information (online).
• Status tab: shows the CP's operational state (RUN, STOP, fault).
• Communication tab: PROFINET diagnostics, link status.
• I/O tab: PNIO_SEND/PNIO_RECV status and last error.

CPU Diagnostic Buffer

From SIMATIC Manager, target the CPU and open PLC > Diagnostic Buffer. Filter for PROFINET-related events:

• Station failure: PROFINET IO Device not reachable.
• Station return: IO Device reachable again.
• PROFINET IO fault: configuration mismatch or hardware diagnostic.
• Module fault: physical I/O module pulled or faulty.

PROFINET Topology Discovery

Use PLC > Ethernet > Discover in SIMATIC Manager to list PROFINET nodes reachable on the local subnet. The discovery uses DCP (Discovery and Configuration Protocol) on UDP port 34964. Devices without a PROFINET device name appear with their MAC address only.

LED Status Decoding (CP 343-1 Lean)

STATUS Code Reference Table

The PNIO_SEND (FC11) and PNIO_RECV (FC12) blocks report status in the STATUS DWORD. The high word typically encodes the FC and protocol layer; the low word encodes the specific condition. The NCM S7 Manual is authoritative for the complete list.

Troubleshooting Matrix

Network Topology and Infrastructure Notes

• Line topology: The CP 343-1's two integrated switch ports support line topology without an external switch. Each additional PROFINET device replaces the need for a separate switch port.
• Star topology: Use an external managed PROFINET switch for star topology. Managed switches support PROFINET Conformance Class B or C and forward DCP correctly.
• Maximum devices: The CP 343-1 IO Controller can manage a maximum number of IO Devices per PROFINET network — verify against the CP's manual for the exact number for your firmware version.
• Cable length: 100 m maximum per copper segment (CAT5e or higher). For longer runs, use fibre with a media converter or a switch with fibre uplinks.
• DCP multicast: DCP discovery uses multicast on UDP port 34964. Many unmanaged switches forward DCP; some managed switches require explicit configuration.

Verification Procedure After Configuration

1. Link verification: Both LINK LEDs on the CP are green steady.
2. Device name verification: IO Device responds to DCP discovery from the IO Controller.
3. Cyclic data exchange: In HW Config online view, the IO Device status shows "OK" with green checkmark.
4. Application-level verification: Toggle an output bit in the IO Controller program; verify the corresponding input bit changes on the IO Device side within one PROFINET update cycle.
5. Diagnostic buffer check: In the CPU's online diagnostic buffer, no PROFINET-related fault entries should be present.
6. STATUS check: After one cycle, PNIO_SEND's STATUS returns 0000 0000 and PNIO_RECV's STATUS returns 0000 0000 with NDR pulsing.
7. Throughput test: Run an extended cyclic test for 1 hour minimum, monitoring STATUS for transient errors. Any non-zero STATUS during steady-state indicates configuration or cabling issues.

Performance and Cycle Time Considerations

• PROFINET update time on the CP 343-1 family is configurable from 1 ms upward, depending on variant and firmware.
• IRT (Isochronous Real Time) requires both hardware and configuration support. The CP 343-1 Lean does not support IRT.
• The CPU's OB1 cycle time plus the PROFINET update time determines end-to-end latency. A CPU with cycle time > PROFINET update time introduces jitter.
• For high-deterministic applications, use CP 343-1 Advanced with IRT and a CPU capable of isochronous mode (e.g., CPU 317T, CPU 319F PN/DP with sync).

Migration and Upgrade Path

When upgrading from a non-PROFINET-capable CP 343-1 Lean (e.g., 6GK7343-1CX00-0XE0) to the PROFINET-capable 6GK7343-1CX10-0XE0:

1. Confirm the STEP 7 version supports the new order number.
2. Replace the CP physically; the slot and backplane interface are compatible.
3. Update HW Config to the new MLFB.
4. Re-assign the PROFINET device name if changed.
5. Verify all FC11/FC12 calls still operate correctly.

When migrating from S7-300 with CP 343-1 to S7-1500 with integrated PROFINET interface: the FC11/FC12 blocks are replaced by native PROFINET I/O access in TIA Portal — the application program logic remains valid but the cyclic call structure changes.

Security and Operational Notes

• PROFINET device name: Treat as security-relevant. A malicious device with a matching device name can hijack IO communication.
• DCP write protection: Some CP variants allow DCP write protection from the TIA Portal / STEP 7 to prevent device name changes after commissioning.
• Network segmentation: Place PROFINET networks on a separate VLAN or physically isolated network from office IT.
• Firmware updates: Apply Siemens security advisories. The CP 343-1 supports signed firmware updates from STEP 7.

Frequently Asked Questions