SIMATIC NET LEAN COMMUNICATION PROCESSOR 6GK7343-1CX10-0XE0 6GK7 343-1CX10-0XE0 6GK7343-1CX1O-OXEO

Siemens 6GK7343-1CX10-0XE0 | SIMATIC NET CP 343-1 Lean — S7-300 Industrial Ethernet Communication Processor, TCP/IP, PROFINET IO Device, Integrated 2-Port Switch, 2×RJ45

Part Number: 6GK7343-1CX10-0XE0

Manufacturer: Siemens AG (Germany)

Switch: Integrated 2-port switch (ERTEC 200 chip) — provides 2 physical RJ45 ports on a single IE interface

Physical Ports: 2 × RJ45 (10/100 Mbit/s)

Communication Protocols:

• TCP/IP (SEND/RECEIVE with and without RFC 1006)
• UDP (SEND/RECEIVE)
• Multicast (UDP)
• ISO-on-TCP transport (RFC 1006)
• Fetch/Write (PG/OP access)
• S7 communication (server function)
• PROFINET IO device

Overview

The Siemens 6GK7343-1CX10-0XE0 is the CP 343-1 Lean — the cost-optimised Industrial Ethernet communication processor for the SIMATIC S7-300 platform.

It occupies a single slot in the S7-300 rack alongside the CPU, and from that slot it manages the S7-300's entire Industrial Ethernet communication: maintaining connections to SCADA servers, HMI panels, and other PLCs; exchanging cyclic process data as a PROFINET IO device; and providing programming access over Ethernet from STEP 7 / TIA Portal workstations.

The "Lean" designation within the CP 343-1 family identifies this as the entry-level variant — lighter on communication resources than the full CP 343-1 (6GK7343-1EX30) but covering all the communication scenarios that the majority of S7-300 Ethernet applications actually require.

TCP/IP with ISO transport (RFC 1006), S7 communication, PROFINET IO device, Fetch/Write, and UDP are all present; what the Lean omits relative to the full CP 343-1 is primarily the extended client-side S7 communication (it supports S7 communication as a server but not as an active client), and certain high-volume simultaneous connection counts.

For HMI connectivity, remote programming, SCADA data collection, and PROFINET IO device integration, the Lean is fully capable.

The integrated 2-port ERTEC 200 switch is a meaningful practical feature.

A conventional single-port Ethernet module requires a separate external switch to connect more than one downstream device at the PLC — a cost and space overhead that adds up across a plant with dozens of S7-300 stations.

The CP 343-1 Lean's built-in 2-port switch means two Ethernet devices (for example, the plant backbone cable and an HMI panel or another device) can connect directly to the CP without any external switch hardware.

This reduces panel footprint, eliminates the switch's power supply and DIN-rail mounting, and simplifies wiring.

Key Specifications

Protocol Suite — What Each Service Does

TCP/IP with SEND/RECEIVE: The fundamental data exchange mechanism. The S7-300 CPU uses STEP 7's AG_SEND / AG_RECV library blocks (or equivalent TIA Portal TCON/TSEND/TRECV blocks) to open TCP connections to remote partners and exchange data.

Without RFC 1006 (raw TCP), this communicates with any TCP/IP device — SCADA servers, PC-based historian systems, third-party controllers — regardless of vendor.

With RFC 1006 (ISO-on-TCP), the transport encapsulates ISO transport layer segments for compatibility with other Siemens devices and older industrial protocols that used ISO transport natively.

UDP with SEND/RECEIVE and Multicast: UDP-based exchange is connectionless — no persistent connection to maintain, lower overhead, appropriate for cyclic data broadcast and one-to-many communication. Multicast enables the CP to send data to multiple receivers simultaneously without repeating the transmission for each receiver, useful for plant-wide status broadcast or time synchronisation.

PROFINET IO Device: The CP 343-1 Lean can operate as a PROFINET IO device — placing the S7-300's I/O data into the cyclic IO exchange of a PROFINET IO controller.

In this role, the S7-300 with CP 343-1 Lean appears to a PROFINET IO controller (perhaps a larger S7-400 or S7-1500 acting as the system master) as a remote I/O device, with the CP managing the PROFINET cyclic data exchange. 

This is the mechanism that allows S7-300 systems to integrate into PROFINET-based plant architectures that predated the S7-300's own PROFINET CPU variants.

Fetch/Write: This protocol allows a remote device (PG, PC, or SCADA system) to directly read from or write to the S7-300's data blocks without any ladder program handling the communication.

Fetch/Write is a polling protocol — the remote device initiates each read or write; the CP responds by accessing the CPU's data directly. 

This simplifies SCADA integration because the SCADA system can map S7-300 data addresses directly to its own tag database.

S7 Communication (Server): The CP 343-1 Lean supports S7 communication in the server role — it responds to S7 communication requests from other S7 devices or from S7-compatible clients (such as Siemens HMI panels communicating in S7 protocol mode).

As a server, it allows other devices to read and write its CPU's data.

The Lean variant does not initiate S7 communication as an active client; for active client S7 messaging, the CPU's own STEP 7 PUT/GET blocks can be used for limited S7 communication without the CP.

Module Replacement Without PG and Initialization via LAN

Two operational features address real maintenance scenarios:

Initialization via LAN means that a new CP 343-1 Lean's IP address and PROFINET device name can be assigned remotely over the Ethernet network without physically connecting a programming device to the PLC.

When a replacement CP arrives at a remote plant, a STEP 7 or TIA Portal workstation on the same Ethernet network assigns the module's network identity — IP address, subnet mask, router — using the NDIS-based network tools included with STEP 7. 

The module is online and functional without a service engineer needing to bring a laptop to the machine.

Module replacement without PG extends this concept: the CP stores its configuration in non-volatile memory.

When a replacement CP 343-1 Lean is installed in the same rack slot, it downloads its configuration from the S7-300 CPU's memory automatically at power-up — the CPU knows what CP configuration belongs in its rack and transfers it to the new module.

The service engineer installs the physical module; the system does the rest.

FAQ

Q1: The CP 343-1 Lean supports S7 communication as a server only. What does this mean for data exchange with other S7 controllers?

In server mode, the CP 343-1 Lean responds to S7 communication requests from other Siemens devices but does not initiate such requests itself.

This means a STEP 7 or TIA Portal engineering station can access the CPU's data, and other S7 controllers that initiate PUT/GET instructions can read and write data in this CPU's data blocks. 

For the CPU on the CP 343-1 Lean side to actively read data from a remote S7 controller over Ethernet, it must use either the STEP 7 PUT/GET function blocks with the CP's STEP 7 S7 connection (which works within the same project) or TCP/IP SEND/RECEIVE if the remote controller also runs a TCP server.

Q2: The integrated switch has 2 RJ45 ports. Does the CP 343-1 Lean support line or ring topologies, or only star?

The 2-port integrated switch supports both star and line (daisy-chain) topologies.

In a line topology, one RJ45 connects to the upstream network device (switch or another CP) and the other connects to the next downstream device — creating a chain of CP 343-1 Lean modules without requiring a central switch for each connection point. 

This is a common topology in panel rows or production lines where controllers are physically arranged in a sequence and a separate infrastructure switch at each location would be inconvenient.

Ring topology (for media redundancy) is not supported by the CP 343-1 Lean; for ring topology with MRP (Media Redundancy Protocol), the full CP 343-1 Advanced (6GK7343-1GX30) is required.

Q3: What is the maximum number of simultaneous TCP connections the CP 343-1 Lean supports?

The CP 343-1 Lean supports a limited number of simultaneous active connections — fewer than the full CP 343-1, which is the primary architectural difference between the two variants. The typical connection resource on the Lean version covers the common scenarios: several TCP connections to SCADA/historian systems, one or two S7 connections to HMI panels, and PROFINET IO device communication.

For high-density multi-connection applications (many simultaneous SCADA clients, multiple concurrent S7 partners), the full CP 343-1 (6GK7343-1EX30) with its larger connection table should be specified.

Q4: Can the CP 343-1 Lean be configured in TIA Portal, or is STEP 7 V5.x required?

The CP 343-1 Lean can be configured in both STEP 7 V5.5 (classic) and TIA Portal (V13 and later, with appropriate hardware support package).

In TIA Portal, the CP appears in the device catalog under SIMATIC NET / S7-300 communication modules and is configured using the CP's properties dialog within the network configuration. 

TIA Portal provides a unified environment for configuring the S7-300 CPU, the CP 343-1 Lean's Ethernet connections, and the PROFINET IO device configuration in a single tool.

Q5: Does the CP 343-1 Lean support PROFINET IO Controller function, or only device?

The 6GK7343-1CX10-0XE0 CP 343-1 Lean supports PROFINET IO Device function only — it cannot act as a PROFINET IO Controller to manage distributed IO devices on a PROFINET network.

For S7-300 systems that need to act as a PROFINET IO Controller (managing ET 200SP, ET 200M, or other PROFINET IO devices), either a PROFINET-capable CPU (such as the CPU 315-2 PN/DP) or the CP 343-1 Advanced (6GK7343-1GX30) with PROFINET IO Controller capability is required. 

The Lean's IO Device function allows it to be managed by an upstream PROFINET IO Controller, which is the appropriate role for an S7-300 acting as a slave or substation in a larger PROFINET system.