20-COMM-E EtherNet/IP Adapter Replacement Guide

Overview

The Allen-Bradley 20-COMM-E is a widely deployed Drive Peripheral Interface (DPI) EtherNet/IP communication adapter. For over two decades, it served as the standard network interface for Rockwell Automation’s "7-Class" PowerFlex variable frequency drives (VFDs), including the PowerFlex 70, PowerFlex 700, PowerFlex 700S, PowerFlex 700H, and PowerFlex 753 (via a reference adapter).

Because Rockwell Automation has transitioned the 20-COMM-E to "End of Life" (EOL) status, automation engineers and maintenance technicians face the challenge of retrofitting obsolete communication networks. This guide delivers the technical specifications, physical and logical compatibility considerations, and step-by-step installation instructions required to replace a malfunctioning or obsolete 20-COMM-E module.

---

Legacy Product Information

The 20-COMM-E connects directly to the internal DPI port of host PowerFlex drives. It translates standard EtherNet/IP industrial protocols into the drive's internal DPI protocol, allowing Allen-Bradley ControlLogix, CompactLogix, and legacy SLC 500 or PLC-5 controllers to monitor, configure, and control the host drive.

Technical Specifications

• Catalog Number: 20-COMM-E
• Protocol: EtherNet/IP (CIP)
• Interface Rate: 10/100 Mbps (Auto-negotiating, Half or Full Duplex)
• Data Consumption: Up to 3.0 Amps at 5V DC (supplied by the host drive's control board via the DPI ribbon cable)
• Diagnostic Indicators: Four status LEDs (PORT, MOD, NET A, NET B)
• Firmware Controls: Features an embedded web server, email notifications, and TCP/IP utility configurations.
• Lifecycle Status: Discontinued / Obsolete

Common Legacy Applications

The module is typically mounted internally within the drive chassis or on an external communication carrier (such as the 20-XCOMM-DC-BASE) to bring EtherNet/IP connectivity to:

• PowerFlex 70 (Standard and Enhanced control)
• PowerFlex 700 (Standard, Vector Control, and Phase II control)
• PowerFlex 700S and 700H
• PowerFlex 753 (using the 20-750-20COMM or 20-750-20COMM-F1 adapter board)
• SMC Flex and SMC-50 Smart Motor Controllers

---

Recommended Replacements

When a 20-COMM-E fails or needs to be phased out, engineers can choose among several replacement paths. The optimal choice depends on whether they are executing a modular repair or performing a complete drive-system modernization.

---

Compatibility Considerations

Replacing a 20-COMM-E requires evaluating physical, electrical, and software limitations to prevent communication dropping or hardware damage.

1. Wiring & Networking Footprint

• Port Count: The 20-COMM-E features a single RJ45 EtherNet/IP port. The upgraded 20-COMM-ER features dual RJ45 ports. If replacing with a 20-COMM-ER to introduce Device Level Ring (DLR) capabilities, ensure you have sufficient physical clearance for two Ethernet cables within the drive's low-voltage wiring compartment.
• Power Draw: Both modules draw power directly from the drive's DPI bus. No external 24V DC power supply is required for the card itself when mounted internally.

2. Physical Footprint and Mounting

• These internal cards mount onto a dedicated plastic bracket inside the drive cover, plugging directly into the drive’s control board via a 20-pin DPI ribbon cable. The ribbon cable and mounting footprint of the 20-COMM-E and 20-COMM-ER are identical.
• Caution: Do not attempt to interface a 22-COMM-E DSI-based adapter with a PowerFlex 7-Class drive. The 22-COMM-E is designed strictly for DSI drives (PowerFlex 4-Class) and will damage the interface or control board if connected via custom conversions.

3. Software & Master Controller Configuration

• System I/O Assembly Configuration: If replacing a 20-COMM-E with a 20-COMM-ER, the CompactLogix/ControlLogix I/O configuration in Studio 5000 / RSLogix 5000 may require modification. If Electronic Keying is set to "Exact Match," the PLC will reject the new 20-COMM-ER until the module profile is updated in the I/O tree or the keying parameter is set to "Compatible Module".
• BOOToP/DHCP Utility: Both modules ship from the factory with DHCP/BOOTP enabled. You must use the Rockwell BOOTP/DHCP tool or a Human Interface Module (HIM) to assign the permanent IP address, Subnet Mask, and Gateway.

4. Firmware Versioning

• Older PowerFlex 700 drives (with Vector Control firmware versions below 4.001) may not recognize some of the advanced Web/Email diagnostic parameters of newer 20-COMM-E or 20-COMM-ER cards. Ensure the Host Drive’s firmware version is compatible with the version of the communication adapter you plan to install. Refer to Rockwell's Product Compatibility and Download Center (PCDC) for compatibility matrix details.

---

Upgrade Benefits

Migrating to the 20-COMM-ER provides significant system architecture advantages over the legacy 20-COMM-E:

1. Device Level Ring (DLR) Support: Enables a redundant network ring topology directly at the drive level. If an Ethernet cable breaks or a switch port fails, the communication path switches in under a millisecond, keeping the drive running and preventing costly downtime.
2. Elimination of External Hardware: Using the 20-COMM-ER in a daisy-chain deployment eliminates the need for expensive managed switches inside drive enclosures or local "tap" modules (like the 1783-ETAP).
3. Enhanced Diagnostics: Improved TCP/IP diagnostic structures and web-interface responsiveness, allowing faster debugging of packets directly via any standard web browser.

---

Common Migration Challenges

• IP Address Retention Loop: A common challenge occurs when setting the IP address via BOOTP, where the adapter assigns the IP address temporarily but reverts to DHCP mode after a power cycle. Solution: Be sure to click "Disable BOOTP/DHCP" in the utility tool after assigning the IP, or change Drive parameter 3 [IP Addr Source] to "Parameters" instead of "BOOTP".
• Physical Space and Bending Radius: In smaller drive enclosures (e.g., PowerFlex 70 Frame A or B), the dual Ethernet cables connected to a replacement 20-COMM-ER can press against the outer drive cover. Use high-quality, right-angle, shielded Cat5e Ethernet cables to prevent mechanical stress on the RJ45 ports.
• Firmware Configuration Mismatch: When swapping a failed module, configuring the new device's parameters is critical. If you have "Automatic Device Configuration" (ADC) enabled in Logix, matching firmware builds is mandatory for automatic parameter download to succeed.

---

Step-by-Step Replacement Procedure

Phase 1: Safety & Isolation

1. Apply LOTO: Ensure all high-voltage sources input to the PowerFlex drive are isolated, locked, and tagged out according to local safety regulations.
2. Verify Zero Energy: Wait a minimum of 5 minutes for the drive's internal DC bus capacitors to fully discharge. Verify zero-voltage status at the DC+ and DC- test points inside the drive with a trusted, calibrated digital multimeter.

Phase 2: Physical Removal and Installation

3. Access the Module: Open the front cover of the PowerFlex drive housing.
4. Disconnect Cables: Gently disconnect the RJ45 Ethernet communication cable from the lower port of the 20-COMM-E.
5. Disconnect DPI Ribbon Cable: Unplug the internal 20-pin DPI ribbon cable from the drive mating connector. Take care not to twist or pull the pins.
6. Unmount the Card: Remove the mounting screws securing the 20-COMM-E adapter to its internal chassis bracket, then remove the obsolete card.
7. Mount the Replacement: Align the replacement 20-COMM-E or 20-COMM-ER card with the mounting bracket pins and secure it using the original hardware.
8. Reattach DPI Ribbon Cable: Plug the 20-pin DPI ribbon cable back into the replacement card's DPI port, ensuring it clicks firmly into place.
9. Attach Ethernet: Plug the Ethernet cable(s) back into the RJ45 port(s).

Phase 3: Setup and Addressing

10. Power Up: Apply main or auxiliary control power to the drive.
11. Verify Bootup Diagnostic LEDs: Check that the PORT status LED glows solid green, indicating a successful host connection. The MOD LED should turn steady green shortly after.
12. Assign the IP Address:
    • Via HIM: Plug an LCD HIM (e.g., 20-HIM-A6) into the drive. Navigate to the communication port menu (typically Port 4, 5, or 6, depending on mounting location). Set parameter 3 [IP Addr Source] to "Parameters". Enter the correct IP addresses in parameters 4 through 7 [IP Addr Dec 1-4], subnet masks in 8 through 11, and gateway in 12 through 15. Cycle power to the drive to commit the configuration.
    • Via BOOTP Utility: Run the Rockwell BOOTP/DHCP Server Utility software on a connected laptop. Locate the MAC address of the new card (printed on the labeling sticker of the card), assign the target IP, and click "Disable BOOTP/DHCP" to lock it into the volatile memory.

Phase 4: PLC Integration Adjustments

13. Validate Controller Connection: In Studio 5000, verify the communication connection. If a revised 20-COMM-ER card was used to replace a 20-COMM-E, adjust the Keying option under the Module Properties to "Compatible Module" or update the system hardware definitions to prevent I/O connection faults.

---

Frequently Asked Questions

Q1: Can I replace a 20-COMM-E with a 22-COMM-E?

No. The 20-COMM-E is a DPI-based adapter designed for 7-Class drives. The 22-COMM-E is a DSI-based adapter designed for 4-Class drives (PowerFlex 4, 40, 400). They operate on entirely different internal communication protocols and pinouts; they are not interchangeable.

Q2: What do the four LEDs on the front of the 20-COMM-E represent?

• PORT: Status of the adapter's connection to the drive's internal DPI bus.
• MOD: Self-diagnostic status of the adapter's micro-controller.
• NET A: Status of the EtherNet/IP connection to the controller.
• NET B: Identifies backup loop/second port activity (this LED is typically inactive on single-port legacy units unless web services are transmitting).

Q3: How do I perform a hard factory reset on a 20-COMM-E card?

You can use a HIM module to navigate to the adapter's port parameters and modify Parameter 19 [Reset Device]. Set this value to "1" (Reset Device) or "2" (Set Defaults). This will wipe the stored IP configuration and revert the card to DHCP/BOOTP mode.

Q4: If I upgrade to a 20-COMM-ER, will my existing PLC program still communicate?

Yes, provided Electronic Keying in your Logix configuration is set to "Compatible Module" or "Disable Keying." The 20-COMM-ER acts as a logical emulator of the 20-COMM-E, ensuring seamless backward protocol compatibility.

---

Related Products & Families

To complete your PowerFlex drive maintenance or migration project, you may also require:

• HIM Modules: 20-HIM-A6, 20-HIM-C3S (For managing parameters directly at the drive door)
• Adapter Options: 20-750-20COMM and 20-750-20COMM-F1 (Enables mounting 20-COMM cards into newer PowerFlex 750 series drives)
• Legacy Protocols: 20-COMM-C (ControlNet), 20-COMM-D (DeviceNet), 20-COMM-Q (ControlNet Coaxial)
• DPI Cables: 20-HIM-H10 (Handheld DPI cable)

---

Need Help?

Whether you need to quickly locate an exact replacement for your legacy Allen-Bradley 20-COMM-E layout or want to procure an upgraded 20-COMM-ER module to modernize your industrial network topology, we can help. Palm Parts Solution can supply new, high-quality refurbished, or reliable surplus industrial automation parts with a comprehensive warranty to ensure your operations stay online. Reach out to our technical sales team today for stock availability and component pricing.