330-00B4

Power Down System Safely

Execute emergency stop, navigate to MOD function, select 'Switch Off' to properly shut down the TNC system.

Never disconnect HSCI cables while system is powered - risk of component damage

Inspect HSCI Cable Connections

Check all HSCI cable connections at the TNC, drive modules, and I/O components. Look for bent pins, corrosion, or loose retention clips on the circular connectors.

HSCI connectors should click audibly when properly seated - partial connections are common failure points

Verify Cable Continuity

Using a multimeter, test continuity on HSCI cable pins according to Heidenhain wiring diagram. Check shield connection integrity.

HSCI uses differential signaling - both + and - lines must have equal resistance

Restart and Monitor

Power up system and observe alarm status. Check PLC program for proper HSCI component addressing in machine parameters.

Use MOD function 'System Info' to verify HSCI component detection before full startup

Identify Failed Component

Note the HSCI address from alarm message. Cross-reference with machine parameter MP7300.x (HSCI component assignment) to identify the specific module.

HSCI addresses are typically sequential starting from 0 - document your system layout

Check Component Status LEDs

Examine the suspected HSCI component for status LED indicators. Red or flashing LEDs typically indicate internal faults.

Some HSCI modules have diagnostic LEDs that show communication status - consult component manual for LED codes

Swap Component Test

If possible, swap the suspected component with an identical known-good module. Update machine parameters MP7300.x if HSCI addresses change.

Ensure exact part number match - different firmware versions can cause compatibility issues

Verify Component Configuration

Check that machine parameters MP7310.x through MP7390.x match the actual HSCI component configuration and firmware versions.

Use TNC diagnostic screen to compare detected vs. configured HSCI components

Locate Bus Termination

Identify the last HSCI component in the chain. Verify termination resistor (120 ohm) is installed only at the end of the bus.

HSCI bus should have exactly one termination resistor at the furthest component from TNC

Measure Bus Impedance

With system powered down, measure resistance between HSCI+ and HSCI- at TNC connector. Should read approximately 60 ohms with proper termination.

Incorrect readings indicate missing, extra, or wrong value termination resistors

Check Cable Length Limits

Verify total HSCI cable length does not exceed 100 meters. Measure actual cable runs and account for any extensions or splices.

Exceeding cable length limits causes signal degradation and intermittent communication failures

Verify Bus Topology

Ensure HSCI components are connected in proper daisy-chain topology, not star or branched configuration.

Draw your HSCI network diagram - star connections are a common wiring error

Access TNC Diagnostics

Navigate to MOD function, select 'System Info', then 'Hardware Info' to check HSCI interface card status and error counters.

Look for communication error counters - high values indicate interface problems

Perform HSCI Loop-back Test

Disconnect all HSCI components and install a loop-back connector at TNC HSCI port. Check if self-test passes with minimal configuration.

Use only Heidenhain-approved loop-back connectors to avoid damage to interface

Check TNC Software Version

Verify TNC software version compatibility with HSCI components using MOD 'Software Info'. Update if necessary through Heidenhain service.

Some HSCI issues are resolved with TNC software updates - check Heidenhain technical bulletins

Document for Service Call

Record exact alarm message, HSCI addresses, component types, and TNC software version for Heidenhain service technician.

TNC interface card replacement requires factory calibration - not a field-replaceable item