Axis-specific interface
| PLC present | |
| Description | The PLC signals that it is present by setting the value to TRUE. 
 | 
| Signal flow | PLC → CNC | 
| ST path | gpAx[axis_idx]^.head.plc_present_w | 
| Data type | BOOL | 
| Value range | [TRUE = PLC present, FALSE] | 
| Access | Write | 
Notice

Only if this value is set to TRUE can the PLC influence the NC kernel by axis-specific control units and be supplied with technology commands by the NC kernel.
| Logical axis number | |
| Description | Logical number of an axis which is unique within the entire system and identifies the axis. The datum is available at this point after controller start-up irrespective of configured axis operation mode or assignment of the axis to a channel. | 
| Signal flow | CNC → PLC | 
| ST path | gpAx[axis_idx]^.head.log_ax_n_r | 
| Data type | UINT | 
| Access | Read | 
| Axis type | |
| Description | Displays the axis type which was configured for this axis in the associated axis parameter list (see P-AXIS-00018). The value is defined by interpreting the axis parameter list at controller start-up. | 
| Signal flow | CNC → PLC | 
| ST path | gpAx[axis_idx]^.head.axis_type_r | 
| Data type | UINT | 
| Access | Read | 
| Axis error | |
| Description | The CNC sets this value to TRUE if the axis is in error state. | 
| Signal flow | CNC → PLC | 
| ST path | gpAx[axis_idx]^.head.error_r | 
| Data type | BOOL | 
| Value range | [TRUE = Axis is in error state, FALSE = No error] | 
| Access | Read | 
| Axis error, not resettable | |
| Description | The CNC sets this value to TRUE if an unresettable error was issued for an axis. | 
| Signal flow | CNC → PLC | 
| ST path | gpAx[axis_idx]^.head.reset_error_locked_r | 
| Data type | BOOL | 
| Value range | [TRUE = Not resettable axis error occurred, FALSE = No error or resettable error occurred] | 
| Access | PLC reads | 
| Data in the axis list parameter P-AXIS-00510 | |
| Description | The data configured by the user in the parameter P-AXIS-00510 in the axis parameter list are available here on the HLI. | 
| Signal flow | CNC → PLC | 
| ST path | gpAx[axis_idx]^.head.customer_val_r[ ] | 
| Data type | ARRAY [0..HLI_AXIS_CUSTOM_MAXIDX] OF UDINT | 
| Access | PLC reads | 
| Updating the HLI | |
| Description | By setting this value to TRUE, the PLC can initiate an update of the entire axis-specific interface area. This value is reset to FALSE by the NC kernel after the update is completed. | 
| Signal flow | CNC → PLC | 
| ST path | gpAx[axis_idx]^.head.f_update_request_rw | 
| Data type | BOOL | 
| Value range | [TRUE = Updating of the HLI activated, FALSE] | 
| Access | Read/write | 
| Special features | Still currently supported, i.e. the HLI is updated in every NC cycle. | 
| Update cycle of the HLI | |
| Description | Using this element, the PLC informs the NC kernel of the number of interrupt cycles the NC kernel may distribute the updating of the axis-specific interface area. This leads to a reduced load on the interrupt task in particular with multi-channel and multi-axis configurations. | 
| Signal flow | PLC → CNC | 
| ST path | gpAx[axis_idx]^.head.n_update_tick_count_rw | 
| Data type | UINT | 
| Unit | Number of interpolator cycles | 
| Access | Write | 
| Special features | Currently not supported, i.e. the HLI is updated in every NC cycle. |