In the field of industrial automation, the PowerFlex 750 series drives by Rockwell Automation are highly regarded for their flexibility, scalability, and rich functionalities. However, precisely because these drives offer numerous optional modules and communication methods, certain fault messages can appear in ways that seem puzzling. Many engineers, for instance, encounter an alert such as “X06 Not Running” or “Port x06 Not Running,” only to open the drive’s enclosure and discover—much to their surprise—that there is no label or port physically marked “X6.” This article aims to address that very phenomenon by clarifying the relationship between logical ports and physical slots. We will delve into why the “X06 Not Running” error occurs, how to troubleshoot it systematically, and—given the possible scenario of drives connected in parallel—how to arrive at practical solutions.
I. Why Can’t We Find “X6” on the Hardware?
1. Logical Ports vs. Physical Slots
In PowerFlex 750 series drives, the term “Port” represents not just a visible hardware interface, but a logical address assigned by the drive firmware. For example, Port 0 usually refers to the Main Control Board, Ports 1 and 2 might be for the front-panel Human Interface Module (HIM) or DPI devices, while Port 6 typically corresponds to the optional module slot, often labeled “Slot C” or “Option Slot 3.” When the drive reports “X06 Not Running” or “Port 6 Adapter Fault,” it is referring to logical Port 6, indicating a module at that position is malfunctioning, rather than some physical connector marked “X6.”

2. Physical Labels Often Appear as “Slot C” or “Option Slot 3”
From a design standpoint, to accommodate various expansion needs in a limited space, the main control board usually includes three to four optional module slots for installing communication adapters, I/O extension cards, or feedback modules. These slots are often labeled “Slot A/B/C” or “Option Slot 1/2/3.” At the software level, the drive maps these slots to Ports 4, 5, 6, and so forth. The main objective is to unify the management of internal and external resources: logical port numbering handles internal data flow, whereas hardware slot labels facilitate on-site module installation and removal.
Consequently, you may see a physical slot labeled “Slot C” or “Option 3” on the drive but not find any silkscreen or marking of “X6” or “Port 6.” If the module in this slot malfunctions or if the slot configuration is incorrect, the system will display an alarm specifically mentioning “Port 6,” leading to a mismatch between how the hardware is labeled and how the firmware identifies it.
II. Possible Causes of the “X06 Not Running” Error
When you see “X06 Not Running” or “Port 6 Not Running,” it generally indicates that the expansion module at Port 6 is in an abnormal state. Common causes include:
- Uninstalled or Empty Slot, Yet Configured The drive might be configured to have a communication or I/O module at Port 6, but the slot is physically empty. Consequently, the system cannot detect the module and raises the error indicating that Port 6 is not running.
- Improper Module Installation or Hardware Failure If the slot does have an expansion module (for example, a 20-750-ENETR Ethernet adapter or a 20-750-DNET DeviceNet adapter) but the module is loose, has poor contact, or is damaged, the drive will perceive it as disconnected. Hardware issues can include defective internal components, as well as firmware incompatibilities.
- Network or Communication Configuration Conflicts For communication modules, if there is a duplicate network address, a mismatched baud rate, or a failure on the fieldbus (cabling short, bus power issues, and so on), the module cannot communicate properly with the drive’s main board. As a result, the drive may show “Port 6 Not Running” or “Comm Loss.”
- Firmware and Configuration Incompatibility When the drive’s firmware version differs substantially from that of the module, the drive might not be able to fully recognize the module’s functionality or might detect an invalid configuration. An older drive firmware may not support certain features in a new adapter.
- Parallel System Configuration Errors In systems where multiple PowerFlex 750 drives are connected in parallel to drive a high-power motor or share a common bus, Port 6 is often used for inter-drive synchronization or redundancy communication. An addressing conflict or a misconfiguration of master/slave roles can cause one of the drives to report a port error.

III. Why You Can’t Find “X6” After Disassembling the Drive
Many users, upon seeing the fault code, first attempt a physical inspection. However, after opening the enclosure, they notice that none of the slot labels match “Port 6,” and they don’t see anything labeled “X6.” This is likely due to the following factors:
- Chassis Labels Only Read “Slot C” The PowerFlex series generally uses letters or numbers to identify slot order, and not a marking such as “X6” or “Port 6.”
- Ports Are Assigned at the Software Level Port 6, Port 5, Port 4, etc., are naming conventions in the drive’s internal DPI or system bus rather than user-facing hardware markings.
- Slot Position May Be Obscured by a Metal Bracket or Circuit Board On higher frame sizes (Frame 8 and above) or particular designs, there may be layered sub-boards or shielding that hides the slot labels. You might need to remove additional parts to locate “Slot C.”
- Empty or Damaged Slots If the slot meant for Port 6 is truly empty or if the module has fallen out or is damaged, there is no direct label for the user to see.
IV. How to Identify and Locate Port 6
- Refer to the Official Installation Manual’s “Slot Layout Diagram” Rockwell documentation typically provides a layout diagram for these optional slots, clearly explaining how “Slot A = Port 4,” “Slot B = Port 5,” “Slot C = Port 6.” Comparing the manual’s diagram with the physical drive helps pinpoint the slot corresponding to Port 6.
- Check Module Information Using HIM or Software By accessing the parameters in the front-panel HIM or by using DriveTools or Studio 5000 software, you can view “Module Info” or “Adapter Info,” where each port’s installed hardware is displayed. If Port 6 shows a communication adapter model, that indicates it is mounted in “Slot C” or “Option Slot 3” physically.
- Physical Observation of the Slot Layout Most PowerFlex 753/755 drives have three side-by-side optional slots on or near the main control board, labeled A, B, and C, or Option 1, 2, and 3. If you see a module in Slot C, that module is the physical carrier for Port 6 from the firmware’s perspective.
- Cross-Check with the Drive’s Fault Log The HIM or the drive configuration software can display a fault queue. If there are repeated references to “Port 6 Adapter Fault” or “Port 6 Comm Loss,” that indicates issues specifically related to the module in Slot C.

V. Steps to Resolve the “X06 Not Running” Error
- Confirm Whether Port 6 Module Is Needed
- If the slot is supposed to be empty, disable or remove the configuration referencing Port 6 in the drive parameters.
- If it does require a module, check whether the module is missing or physically damaged.
- Examine Physical Installation and Connections
- Power down the drive, remove the module, inspect for bent pins or contamination, then re-seat it firmly.
- For communication modules, make sure the bus cables and terminators are set up properly, and that bus power is available.
- Diagnose Network Conflicts
- For DeviceNet or other fieldbus protocols, ensure all device addresses are unique and the baud rate matches.
- In parallel systems, verify that each drive’s address and roles (master/slave) do not conflict.
- Check Drive and Module Firmware Compatibility
- Certain older drives might not recognize newer modules. Consult the official Rockwell documentation and release notes, and consider firmware updates that support the required module features.
- Factory Reset or Reconfigure If Necessary
- If hardware is intact but the issue persists, try restoring Port 6 parameters to defaults and then reapply correct settings. This step can help resolve initialization failures caused by parameter corruption.
VI. Avoiding Port Faults in Parallel Applications
When multiple PowerFlex 750 drives run in parallel to drive a high-power motor or share a common bus, they often rely on inter-drive communication and synchronization. Common issues leading to “X06 Not Running” in such scenarios include:
- Address Conflicts: For instance, if each drive has a DeviceNet module with the same node address, then some modules will drop offline.
- Improper N-1 Redundancy Configuration: If one drive is designated as the master and another is the follower, a misconfigured follower may cause the master drive to detect that Port 6 is down, stopping the entire system.
- Missing Synchronization Signals: If the optical fiber or sync cables between parallel drives are disconnected, the drive can report a fault for the relevant port.
To prevent such faults, proper planning is essential from the outset—assigning unique addresses, defining consistent master/slave roles, and thoroughly testing each drive individually, then in collective operation. Regularly monitoring network status and each drive’s port modules will help you detect potential problems early.
VII. Conclusion
The message “X06 Not Running” may initially seem mysterious or perplexing, but in reality, it reflects the PowerFlex 750 drive’s internal scheme for managing expansion modules via logical ports. The drive firmware assigns port numbers to identify each module; as soon as a particular module is missing, malfunctioning, or misconfigured, the drive displays an alert naming that logical port—for example, Port 6.
Effective troubleshooting requires a solid understanding of how hardware slots (such as Slot C) correspond to these logical ports, along with targeted use of official documentation or diagnostic tools. In multi-drive, parallel systems, you must also pay close attention to address settings, role assignments, and synchronization signals to ensure each drive operates in harmony.
By applying the concepts outlined here, you can significantly reduce downtime and confusion related to “X06 Not Running” or similarly cryptic errors. This knowledge also lays a robust foundation for future maintenance and potential system expansions, where familiarity with port-slot logic and network coordination becomes even more valuable.