126-012E

Identify affected CC index

Note the CC index number shown in the %1 parameter of the alarm message. This identifies which communication controller has too many UM units assigned.

The CC index corresponds to the physical CC slot position or logical CC numbering in your machine configuration.

Count physical UM connections

Trace the DRIVE communication cable from the identified CC module and count all UM units in the daisy-chain topology connected to that specific CC controller.

Power down the machine before tracing cables in the electrical cabinet to prevent shock hazard.

Redistribute UM units

If more than 8 UM units are found on one CC, physically reconnect UM units to distribute them across multiple CC controllers. Maintain proper cable termination at the end of each DRIVE bus segment.

Balance axes logically - put related axes (e.g., gantry pairs) on the same CC when possible for synchronized communication.

Update drive configuration

Access MOD > SYSTEM CONFIGURATION > CfgDriveController and modify the CC assignment for each relocated UM unit to match the new physical topology. Save configuration and reboot.

Use SEL to select each axis and verify its AxisCCIndex parameter matches the physical CC connection.

Access drive controller configuration

Press MOD key, select SYSTEM PARAMETERS, then navigate to CfgDriveController section to view all UM unit assignments and their associated CC indices.

Use the filter function to display only axes assigned to the problematic CC index shown in %1.

Verify physical vs logical topology

Cross-reference each UM unit's physical CC connection against its configured AxisCCIndex parameter. Look for mismatches where the parameter doesn't match actual wiring.

Create a wiring diagram showing CC index, UM address, and axis name for future reference during troubleshooting.

Correct CC index assignments

For each misassigned UM, edit the AxisCCIndex parameter to match the physical CC controller it's connected to. Ensure no more than 8 UM units share the same CC index value.

Incorrect CC assignment will prevent axis communication - verify wiring before changing parameters.

Save and restart control

Save the modified configuration parameters and perform a complete control restart (not just NC reset). Verify alarm does not reappear during drive initialization sequence.

Monitor the PLC Program Run window during startup to observe drive enumeration and confirm proper UM detection.

Check UM address switches

Power down and physically inspect the rotary address switches on each UM unit connected to the affected CC. Document each UM's set address value.

Disconnect power before opening drive cabinets. Wait for DC bus capacitors to discharge (check voltage indicator LEDs).

Identify duplicate addresses

Compare all documented UM addresses on the same CC bus segment. Each UM must have a unique address value within its CC communication group.

Heidenhain UM addresses typically range from 0-7 or 0-15 depending on system configuration. Consult your machine documentation for the addressing scheme.

Reassign conflicting addresses

Set unique addresses on any UM units sharing duplicate values. Use sequential numbering within each CC group for easier troubleshooting and logical organization.

Take photos of address switch settings after making changes for maintenance documentation.

Update configuration database

In MOD > CfgDriveController, verify that the AxisDriveAddress parameter for each axis matches its physical UM address switch setting. Update any mismatches.

Some controls auto-detect UM addresses during enumeration, but explicit configuration prevents detection errors.

Verify with drive diagnostics

Power up and access MOD > DIAGNOSTICS > DRIVE STATUS to confirm each UM is detected with correct address and CC assignment. Check for duplicate entries.

The drive status display shows real-time enumeration - watch for any UM units appearing multiple times in the list.