Allen-Bradley 20-COMM-E Communication Adapter – PowerFlex 700 Series

Allen-Bradley 20-COMM-E: EtherNet/IP Peripheral Adapter for PowerFlex 700-Series AC Drives

The 20-COMM-E is a peripheral communication adapter engineered by Rockwell Automation for the PowerFlex 70, 700, 700H, 700S, 700L, 7000, and 7000L variable-frequency drive families. Its function within a control architecture is unambiguous: it translates the drive’s internal DSI (Drive Serial Interface) backplane traffic into EtherNet/IP CIP (Common Industrial Protocol) frames, enabling a Logix-based controller to exercise deterministic command authority over motor speed, torque reference, and fault state — all over standard IEEE 802.3 infrastructure.

In a typical ControlLogix or CompactLogix topology, the 20-COMM-E participates as a Class 1 I/O connection target. The scanner (PLC) establishes a cyclic connection at a configurable RPI (Requested Packet Interval), typically 10–20 ms, during which the controller writes output assembly data (speed reference, control word) and reads input assembly data (output frequency, status word, fault code) in a single UDP/IP exchange. This deterministic exchange model is what separates EtherNet/IP from generic TCP/IP polling — the adapter does not wait for a request; it responds on a fixed schedule governed by the CIP connection parameters negotiated at connection open.

The adapter mounts directly into the drive’s peripheral port — a proprietary 20-pin DSI connector located on the control board of compatible PowerFlex drives. No external power supply is required; the adapter draws operating power from the drive’s internal 5 V DSI bus. This architecture eliminates field wiring between the adapter and the drive’s control logic, reducing both installation time and potential noise ingress points.

For facilities operating mixed-generation PowerFlex fleets, the 20-COMM-E provides a single SKU that spans the entire 700-series product line. A maintenance engineer can stock one adapter type and deploy it across PowerFlex 70 (20A), 700 (20B), 700H (20C), 700S (20D), 700L (20G), 7000 (20P), and 7000L (20R) frames — a meaningful reduction in spare-parts inventory overhead for large installations.

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Technical Parameters

Hardware Logical Analysis

The 20-COMM-E’s internal architecture centers on a dual-processor design: a dedicated DSI protocol engine handles the serial link to the drive’s control board at a fixed 125 kbps baud rate, while a separate Ethernet MAC/PHY subsystem manages the 10/100 Mbps network interface. The two processors communicate through a shared-memory buffer, which decouples the deterministic DSI polling cycle from the asynchronous Ethernet frame handling. This separation is architecturally significant — it means network congestion or a momentary Ethernet collision event does not introduce jitter into the drive’s internal control loop timing.

The DSI bus itself uses a master-slave polling model. The drive’s control board is the master; the 20-COMM-E is one of up to five peripheral slaves addressable on the bus. Each DSI transaction is a fixed-length frame: a 1-byte address, a 1-byte command, up to 4 bytes of data, and a 1-byte CRC. The adapter maps a subset of drive parameters — specifically the output assembly (speed reference, control word) and input assembly (output frequency, DC bus voltage, fault code, status word) — into a CIP I/O assembly object. This mapping is configurable via explicit messaging during commissioning, allowing the integrator to select which drive parameters appear in the cyclic I/O data.

From an EMC standpoint, the adapter’s RJ-45 port incorporates integrated magnetics (transformer isolation) that provide 1500 V AC galvanic isolation between the Ethernet cable shield and the adapter’s internal ground plane. This isolation is critical in drive enclosures where the DC bus switching transients (dV/dt rates of 5–10 kV/μs on 480 V drives) can couple capacitively into signal wiring. The transformer isolation prevents these transients from propagating onto the plant Ethernet backbone.

The adapter supports Device Level Ring (DLR) topology when used with a DLR-capable managed switch (e.g., Stratix 5700). In DLR mode, the adapter participates as a ring node, not a ring supervisor. The ring supervisor (typically the managed switch or a ControlLogix module) monitors ring integrity and executes a sub-3 ms failover if a cable break is detected — a recovery time that is transparent to the CIP I/O connection’s RPI timer in most applications.

System Integration Benefits

• Deterministic I/O Latency: Class 1 CIP connections deliver cyclic data at a configurable RPI (minimum 2 ms), providing the PLC with a predictable, bounded update rate for speed feedback and control word delivery — essential for coordinated multi-drive motion sequences.
• Transparent Drive Diagnostics: Fault codes, warning bits, output current, DC bus voltage, and heatsink temperature are all accessible as explicit CIP attributes, enabling the SCADA or HMI layer to display drive health without requiring a separate serial connection or keypad interrogation.
• Remote Parameter Read/Write: Studio 5000 MSG instructions can read or write any drive parameter (by parameter number) over the EtherNet/IP connection, eliminating the need for a laptop and USB-to-DSI cable during commissioning or parameter adjustment in the field.
• Logix Add-On Profile (AOP) Support: Rockwell’s AOP for the 20-COMM-E integrates directly into Studio 5000, presenting the drive’s I/O assembly as structured tags (e.g., Drive.Speed_Ref, Drive.Output_Freq) rather than raw integer arrays — reducing ladder logic complexity and improving code readability.
• BOOTP/DHCP Address Management: In large installations with centralized DHCP servers, the adapter can receive its IP address automatically at power-up, simplifying network commissioning and ensuring address consistency across drive replacements.
• DLR Ring Topology Compatibility: Supports Device Level Ring for high-availability network architectures, providing sub-3 ms failover on cable fault without requiring a redundant controller or additional network hardware.
• Cross-Generation Drive Compatibility: A single 20-COMM-E SKU covers seven PowerFlex drive families, allowing maintenance teams to standardize on one spare adapter type across mixed-vintage installations — reducing inventory carrying cost and simplifying procurement.
• EDS File Availability: The adapter’s Electronic Data Sheet (EDS) file is available from Rockwell’s PCDC portal, enabling third-party EtherNet/IP scanners (non-Logix) to configure and communicate with the drive using standard ODVA tooling.
• Scalable Network Architecture: Multiple 20-COMM-E adapters can coexist on a single Ethernet segment without address conflicts, supporting installations ranging from a single drive to hundreds of drives on a segmented plant network.
• Firmware Upgrade Path: Adapter firmware is field-upgradeable via the ControlFLASH utility over the EtherNet/IP connection, allowing security patches and feature updates to be applied without physical access to the drive enclosure.

Quality Assurance & Global Logistics

Every 20-COMM-E unit shipped from our Xiamen, China facility is sourced from verified supply channels with full lot traceability. Prior to dispatch, each adapter undergoes a structured inspection protocol: visual examination of the RJ-45 connector, DSI 20-pin interface, and housing for mechanical integrity; label and serial number authentication cross-referenced against known genuine unit profiles; and a power-on functional check confirming Ethernet link establishment and DSI bus enumeration.

Units are packaged in anti-static (ESD) bags with desiccant, sealed in moisture-barrier pouches, and placed in rigid foam-lined cartons rated for international air freight handling. This packaging specification meets IEC 61340-5-1 ESD protection requirements and IATA Dangerous Goods Regulations for electronic components.

Shipping is executed via DHL Express, FedEx International Priority, and UPS Worldwide Express — all with door-to-door tracking and commercial invoice documentation for customs clearance. Standard in-stock lead time is 1–3 business days from order confirmation. All units carry a 12-month quality warranty from the shipment date, covering manufacturing defects and functional failures under normal operating conditions.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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