Configuring SIMATIC Industrial Ethernet ISO Protocol for CP443-1

Overview

SIMATIC Industrial Ethernet (IE) supports several transport layers on top of an IEEE 802.3 / Ethernet II physical link. Among them, the ISO Transport protocol (ISO/IEC 8073 class 4) and ISO-on-TCP (RFC 1006) are the two connection-oriented variants most often used with the CP443-1 communications processor on the S7-400 family. The ISO Transport protocol operates at layer 2/4 of the OSI model and routes frames by destination MAC address, which is exactly the behaviour required when a CP443-1 has been pre-configured at the factory with a fixed MAC address and no IP address is available. This reference documents the full procedure to install the SIMATIC ISO protocol stack on a Windows engineering station, configure an ISO Transport connection in NCM S7 / STEP 7, target the partner CP443-1 by its MAC address, and verify the connection with the standard diagnostics tools.

The procedure is based on the official Siemens FAQ How do you configure an ISO-on-TCP connection for data exchange between S7-300 and/or S7-400 by way of Industrial Ethernet CPs?, the application example Ethernet communication (ISO Transport protocol) between SIMATIC S5 and SIMATIC S7-1500, and the AutomationDirect integration guide Siemens Ethernet ISO over TCP/IP (S7-1200 or S7-1500) Setup.

Protocol Stack Comparison: ISO Transport vs ISO-on-TCP vs TCP/IP

Before installing any software, clarify which transport the application needs. The wrong choice produces an "0x0001" connection-error entry in the CP443-1 diagnostic buffer, or a passive-connection waiting state that never completes.

Use ISO Transport when the partner CP443-1 ships with a fixed, non-IP configuration. Use ISO-on-TCP (the default in STEP 7 V5.x NetPro) when an IP address is available and a routed network is in use.

Prerequisites

1. Engineering station: Windows 7 SP1 / Windows 10 (64-bit) with STEP 7 V5.6 or V5.7 and the NCM S7 option installed. STEP 7 Basic in TIA Portal is insufficient for the legacy CP443-1 family; the SIMATIC S7-400 is programmed with the classic STEP 7 V5.x toolset.
2. SIMATIC NET CD (version 14 SP1 or higher) or the SIMATIC NET PC Software component that ships with STEP 7 V5.6+. This installer is what binds the SIMATIC Industrial Ethernet (ISO) Protocol to the network interface.
3. CP443-1 firmware at V2.x or higher (6GK7 443-1EX20-, -1EX30-, -1EX40-, or -1GX20-0XE0). The CP443-1 EX11-0XE0 (the first IT-capable variant) only supports ISO Transport on Ethernet, not ISO-on-TCP until V5.0 firmware is loaded. Check the firmware on the factory computer with CP->Online -> Firmware in NetPro.
4. Administrator rights on the engineering station. The ISO protocol driver installs a NDIS 5/6 intermediate driver; non-admin installs silently fail.
5. Known MAC address of the target CP443-1. The address is printed on the front label of the module (format 08-00-06-xx-xx-xx for Siemens) and can be read on the factory computer via Start -> Run -> cmd -> arp -a or with SIMATIC Manager's Accessible Nodes on the factory bus.

Installing the SIMATIC Industrial Ethernet ISO Protocol Stack

The Windows TCP/IP stack does not include the SIMATIC ISO Transport protocol. The driver must be installed and bound to the physical NIC.

1. Insert the SIMATIC NET DVD. If the installer autoruns, choose Install -> SIMATIC NET PC Software -> Individual Installation. If not, run setup.exe from the root of the DVD.
2. In the component tree, enable SIMATIC NET Driver -> SIMATIC Industrial Ethernet (ISO) Protocol. The installer also offers the RFC 1006 (ISO-on-TCP) and the S7 Protocol; leave the defaults selected so the project can switch between transports later without a re-install.
3. Accept the prompt that binds the ISO protocol to every detected Ethernet adapter. The binding can be re-checked later in Control Panel -> Network and Sharing Center -> Adapter Settings -> Properties; the SIMATIC Industrial Ethernet (ISO) Protocol entry must be checked for the local NIC that physically connects to the plant bus.
4. Reboot. After reboot, open Start -> Programs -> SIMATIC -> SIMATIC NET -> Commissioning -> Set PC Station. The CP443-1 partner is not a PC station, so do not change anything here; instead, only verify that the local index 1 (or higher) is the NIC with the ISO protocol bound.
5. Confirm with a quick ARP lookup. From the command line on the engineering station connected to the plant bus:

   arp -a
   ping <known IP of the factory computer on the same subnet>
   arp -a

   The factory computer's MAC entry must appear in the second listing; if it does not, the ISO protocol is not bound to the active interface.

Configuring the CP443-1 in HW Config

Open the S7-400 project in SIMATIC Manager and launch HW Config. The CP443-1 must be inserted in the S7-400 rack (slot 6, like every CP443-1 in a UR2/UR1/CR3 rack).

1. From the hardware catalog, navigate to SIMATIC 400 -> CP-400 -> Industrial Ethernet -> CP443-1. The exact order number shown in HW Config must match the part number printed on the front of the module (for example, 6GK7 443-1EX40-0XE0 for the latest ISO/IT variant). Using a generic placeholder order number causes a firmware mismatch at download and the CP rejects the configuration with diagnostic event 0x031A.
2. Double-click the CP443-1 to open the property dialog. On the General tab leave the slot address at the default.
3. On the Parameters tab, set the MAC address field to the value read from the factory computer. In the legacy CP443-1 property dialog, MAC is configured as a six-byte colon- or hyphen-separated string. The factory computer's ipconfig /all against the same NIC will show the same address; the CP443-1 uses this MAC as the Source MAC on every outbound frame.
4. On the Time-of-day Synchronization sub-tab, disable NTP unless the plant bus already provides it. Enabling NTP on an ISO-only bus causes the CP to broadcast UDP frames that never reach a server and the diagnostic buffer fills with "NTP server unreachable" warnings.
5. Save and compile (Station -> Save and Compile). The compilation produces the system data blocks SDB for the connection table that the next step will populate.

Setting Up a MAC-Based ISO Transport Connection in NetPro

NetPro is the connection editor for the S7-400. The CP443-1 supports the following connection types: S7 connection, ISO Transport, ISO-on-TCP, TCP, UDP, and S7-mail (FETCH/WRITE for HMI). For a MAC-only partner, choose ISO Transport Connection.

1. In NetPro, right-click the CP443-1 in the rack and choose Insert New Connection.
2. In the connection dialog, set Partner to unspecified (this is mandatory for a MAC-only target; choosing a known partner PLC would require an IP address).
3. Set Connection Type to ISO Transport Connection. The interface is auto-set to the local CP443-1.
4. Click Properties -> Address Details. The following table documents the mandatory parameters:

5. Confirm with OK. The connection is now shown in the NetPro matrix as a yellow line (configured but not loaded).
6. Select PLC -> Download to Target Station -> Connections and Routing. STEP 7 will push the modified system data to the S7-400 CPU. The CP443-1 internally stores the connection in SDB 110 .. SDB 119; the exact SDB depends on the connection number.
7. Run PLC -> Compile and Download All if the CP443-1 firmware was upgraded during the same session; the SDBs for the firmware parameters and the connection parameters are interdependent.

Connection Parameters Reference

The following block summarises every parameter that NetPro exposes for an ISO Transport connection on the CP443-1 and the practical value used in a typical factory-floor migration.

Integrating an HMI Panel on the Same ISO Bus

Some plants add a vendor HMI (for example, an AutomationDirect C-more panel) on the same ISO bus. The Siemens Ethernet ISO over TCP/IP setup guide documents the recommended approach.

1. For native TCP/IP HMIs, use ISO-on-TCP (RFC 1006) instead of ISO Transport. The CP443-1 will then answer on TCP port 102.
2. Set the panel's IP Address to a free address on the same subnet as the CP443-1 (the CP443-1 must have its IP configured in HW Config when ISO-on-TCP is used; ISO Transport does not require an IP address).
3. Use the Siemens port settings documented in the C-more help: Port = 102, Protocol = ISO-on-TCP, TSAP = 10.01 on the PLC side, and the corresponding TSAP = 10.01 on the panel driver for an S7-200/300/400 connection.
4. If the HMI must ride a MAC-only bus (no IP), use a third-party ISO Transport stack on the panel; the C-more firmware does not include one, so an external protocol converter (such as a Helmholz DP/ISO-Coupler or a Phoenix Contact FL mGuard) is required. Reserve one CP443-1 port for the converter IP and let the converter forward ISO Transport to the C-more's TCP socket.

Bridging an S5 Partner to a Modern S7-1500

Older plants still run an AG S5 on the same bus. The application example Ethernet communication (ISO Transport protocol) between SIMATIC S5 and SIMATIC S7-1500 shows the bridging pattern:

• An S5 with a CP1430 (or CP143) only speaks ISO Transport on Ethernet. Configure the S5 side in COM 143 with the partner MAC = S7-1500's PROFINET interface MAC and partner TSAP = 10.01.
• On the S7-1500, the CP1543-1 (or the integrated PROFINET interface) is configured in TIA Portal as an ISO Transport Connection. The TSAP is the S7-1500 slot / connection-resource encoding, typically 01.01.
• The S7-1500 acts as a passive partner; the S5 with CP1430 must be the active initiator, otherwise the S5 keeps the connection in LISTEN forever.

The S5-to-S7-1500 path is included here because it is the most common reason an engineer ends up needing the legacy ISO Transport driver on a modern engineering station that otherwise only runs TIA Portal.

Diagnostics and Verification

After the download, verify the connection with the standard tools.

1. In NetPro, right-click the connection row and select Connection Status. The state must report ESTABLISHED. A value of PARTNER_NO_CONNECT means the local CP could not reach the partner MAC; check cabling, switch port VLAN, and the configured remote MAC.
2. Open the CP443-1 online diagnostics with PLC -> CP Diagnostics -> Diagnostic Buffer. The most useful entries for an ISO Transport problem are:

3. Issue a manual read from the partner with Accessible Nodes -> Read Online. A successful read confirms the ISO Transport path end-to-end.
4. For a non-STEP 7 partner, send a single PUT/GET via a small STL snippet:

   CALL FC5   // AG_SEND
     ID    := W#16#1     // connection ID from NetPro
     LADDR := W#16#1000  // I/O address of the CP443-1 in HW Config
     SEND  := P#DB100.DBX0.0 BYTE 240
     LEN   := 240
     DONE  := M10.0
     ERROR := M10.1
     STATUS:= MW12

   If STATUS = 0 and DONE = 1, the ISO Transport connection is up and the S7-400 can write to the partner.

Troubleshooting Matrix

Engineering Notes

• The CP443-1 cannot be configured to bridge between an ISO Transport bus and a TCP/IP bus; the routing is layer-2 only. A dedicated CP443-1 Advanced (6GK7 443-1GX20-0XE0) is required for IT/Internet routing.
• MAC addresses on a CP443-1 are always writable in HW Config regardless of what the field engineer sees. Siemens does not impose a MAC lock at the factory, but overwriting a MAC of an already-running plant disrupts the bus and is the most common cause of a "works on one PC but not on the other" behaviour.
• STEP 7 V5.6 supports CP443-1 up to order number 6GK7 443-1EX40-0XE0; for any 6GK7 443-1EX50-0XE0 modules a HSP (Hardware Support Package) must be installed. The HSP is delivered as a free download from the Siemens Online Support and is not part of the standard STEP 7 media.
• Always download the CP443-1 firmware using the same SIMATIC Manager session that owns the project; mixing firmware packages between two engineering stations is the most common cause of an 0x031A error on a recently migrated project.