EtherNet/IP on Siemens ERTEC 200P: Implementation Reference

Overview

The Siemens ERTEC 200P is an ASIC designed primarily for PROFINET device development, integrating a dual Ethernet PHY, ARM9 core, and on-chip peripherals targeting industrial I/O. Because the silicon exposes Layer 2 access through the PROFINET Device Development Kit (DevKit), EtherNet/IP — which is built on CIP over standard Ethernet/TCP/UDP — can be ported to the same hardware without modification. This reference describes the protocol requirements, software stack components, and licensing constraints needed to run an EtherNet/IP node on the ERTEC 200P.

Hardware Platform: ERTEC 200P Capabilities

The ERTEC 200P integrates the resources required for both PROFINET and EtherNet/IP device implementations:

• Integrated dual 100 Mbit/s Ethernet PHY supporting switch-internal cut-through and store-and-forward modes. The PHY is protocol-agnostic; the "PROFINET-IP" chapter label in the datasheet refers to PROFINET's use of the PHY, not an exclusive hardware lock.
• ARM926EJ-S core (typically 250 MHz) for application and stack execution.
• External memory interface for SDRAM/SRAM/Flash to host the protocol stack, CIP object library, and application code.
• Enhanced Real-Time Ethernet Controller (ERTEC) MAC with IRT-aware cut-through, but usable as a standard IEEE 802.3 MAC when PROFINET RT/IRT are disabled.

Protocol Foundation: CIP on Ethernet

According to ODVA publication PUB00138R8 CIP on Ethernet, EtherNet/IP adapts the Common Industrial Protocol (CIP) to standard Ethernet transport. CIP provides a unified object model that is identical across DeviceNet, ControlNet, and EtherNet/IP — only the link-layer encapsulation differs. On Ethernet, CIP rides on:

As outlined in the Rockwell Automation EtherNet/IP white paper, a device can behave as either an Adapter (server I/O device) or Scanner (master/PLC-class) node. Adapter functionality is the lowest-effort entry point on the ERTEC 200P.

Software Stack Components on the DevKit

The PROFINET Device Development Kit for ERTEC 200P exposes its TCP/IP subsystem as a reusable wrapper. Per the Siemens TCP/IP Stack manual, this component is responsible for:

• TCP and UDP socket handling, including listen/accept, connect, send, receive.
• IP packet send/receive through the ERTEC MAC driver.
• ARP, ICMP, and optional IGMP/MLD support.
• BSD-style socket API for application code.

For EtherNet/IP, the DevKit TCP/IP stack supplies the IETF-defined transport layer functions. Above it, the application supplies the CIP encapsulation layer and CIP object library.

Layer 2 Access

The DevKit exposes Layer 2 (raw Ethernet) send/receive hooks, which means the application can emit EtherType 0x0800 (IPv4), 0x0806 (ARP), 0x88CC (LLDP), and 0x88A4 (EtherNet/IP encapsulation header on UDP/TCP) without interference from PROFINET RT/IRT framing. To free the MAC for non-PROFINET traffic:

1. Disable PROFINET RT/IRT scheduling in the DevKit configuration.
2. Release the IRT time-slot reserves; switch the MAC to standard store-and-forward.
3. Register an EtherType filter for 0x0800 and 0x88CC so that standard Ethernet/IP/LLDP frames reach the socket layer.

Required CIP Objects for an Adapter

An EtherNet/IP Adapter must expose a defined subset of CIP objects. Minimum object list for a class-A adapter:

Implementations must respond to the Get_Attribute_Single and Set_Attribute_Single services (service codes 0x0E, 0x10) on the supported instances. Instance 0 (class attributes) and Instance 1 of the Identity object must always be reachable.

IGMP and Multicast Considerations

EtherNet/IP uses IP multicast for Class 1 and Class 3 implicit I/O connections (UDP port 2222, multicast group 239.192.1.0–239.192.1.255 reserved for CIP transport class). Although ODVA does not mandate IGMPv2/v3 join support on simple adapters, leaving it out means the device depends on a flood-from-switch behavior and may not scale on managed networks.

• Recommended: Implement IGMPv2 join/leave for the multicast groups assigned by the scanner during Forward_Open parameter negotiation.
• Acceptable for non-managed networks: Skip IGMP; treat the MAC multicast filter directly using the multicast address mask exposed by the ERTEC MAC registers.
• Hardware filter: Program the ERTEC 200P hash table for the assigned multicast destination so non-subscribed frames are dropped at the MAC.

Transport Layer Configuration

UDP Port 2222 — Implicit I/O

The CIP encapsulation layer for implicit messaging uses UDP port 2222. On the ERTEC 200P, configure the TCP/IP wrapper to:

• Bind a UDP socket to 0.0.0.0:2222.
• Enable receive for the multicast groups assigned at runtime.
• Set DSCP field per CIP Connection object (typically 0x2E for Class 1 priority, 0x00 for Class 3).

TCP Port 44818 — Explicit Messaging

All CIP explicit messaging and encapsulation commands (ListIdentity, SendRRData, SendUnitData) traverse TCP port 44818. The DevKit TCP/IP stack supports up to 16 concurrent TCP connections; the ERTEC 200P resource ceiling is comfortable for an Adapter role.

Encapsulation Header

Every explicit message begins with a 24-byte encapsulation header. The application must parse:

struct EncapsulationHeader {
    uint16_t command;
    uint16_t length;
    uint32_t session_handle;
    uint32_t status;
    uint8_t  sender_context[8];
    uint32_t options;
};

Supported commands per ODVA: 0x0065 ListIdentity, 0x006F SendRRData, 0x0070 SendUnitData, 0x0064 RegisterSession, 0x0066 UnregisterSession.

ODVA Membership and Stack Licensing

The CIP specification is publicly available, but devices bearing the ODVA "EtherNet/IP Conformant" mark require conformance testing. Practical licensing paths:

Implementation Path: Adapter Role

The simplest ERTEC 200P EtherNet/IP deployment is an Adapter. Implementation steps:

1. Project setup: Start from the PROFINET DevKit sample; remove PROFINET-specific task scheduling.
2. TCP/IP layer: Reuse the DevKit TCP/IP wrapper. Configure IP addressing via DHCP or static; populate the TCP/IP Interface object (0xF5).
3. EtherNet/IP encapsulation: Implement a thread/task handling the TCP 44818 listener and the encapsulation command parser.
4. CIP object database: Implement Identity, Message Router, Connection Manager, Assembly, Connection, Parameter, TCP/IP Interface, and EtherNet/IP Link objects.
5. I/O connection engine: Handle Forward_Open (service 0x54) and Forward_Close (0x4E) on the Connection Manager. Track Class 1 and Class 3 connection instances in the Connection object.
6. Multicast plumbing: Join the multicast group on Forward_Open, leave on Forward_Close.
7. Diagnostic counters: Populate the EtherNet/IP Link object counters for transmit/receive errors, dropped frames, and octet counts.

Memory Footprint

Indicative RAM/ROM partitioning for an Adapter-only stack on ERTEC 200P:

Leave at least 1 MB SDRAM headroom for application expansion; the ERTEC 200P typically pairs with 8–32 MB SDRAM.

Verification and Conformance Testing

Once the stack is operational, validate against the ODVA EtherNet/IP CT (Conformance Test) suite:

1. Wire capture: Run Wireshark with an EtherNet/IP dissector enabled. Verify ListIdentity response, RegisterSession/UnregisterSession handshake, and Forward_Open parameter negotiation.
2. Behavior against reference scanner: Use Rockwell Studio 5000 Logix Designer or a third-party CIP scanner to drive the adapter under nominal and fault conditions.
3. Stress test: Cycle power, force IP address conflict, test duplicate session rejection, and verify Connection Timeout multiplier behavior (typically 4x RPI).
4. EDS file: Publish an EDS (Electronic Data Sheet) describing object instances, parameter defaults, and connection paths so the scanner can configure the adapter offline.

Troubleshooting Matrix

Field-Proven Caveats

• Clock drift: The DevKit's internal PTP stack may still emit sync frames; ensure PROFINET sync is fully disabled to avoid spurious multicast frames confusing the scanner.
• PHY LED behavior: LED signaling is PROFINET-defined; expect non-standard link/activity behavior on EtherNet/IP. External LEDs may need to be re-mapped in firmware.
• EMC: The hardware meets PROFINET EMC profiles; this covers EtherNet/IP but field installations should still observe CIP volume 2 recommended cable categories (Cat 5e minimum, Cat 6A for industrial sites > 50 m).
• Concurrent PROFINET + EtherNet/IP: Theoretically possible but unsupported by the DevKit build chain and ODVA/SIEMENS documentation. Run only one industrial Ethernet protocol at a time.

Summary of Constraints

The ERTEC 200P silicon, exposed through the Siemens DevKit, supports EtherNet/IP Adapter implementation without hardware modification. The TCP/IP wrapper already in the DevKit satisfies IETF UDP/TCP requirements. IGMP remains an engineering decision. CIP objects must be implemented to ODVA specification. The only barriers are software effort and conformance licensing. A Vendor Member ODVA relationship, or a licensed stack, is the recommended path for production deployment.