Introduction

The basic mechanisms implemented for the block search are contained in the functional description "Block search" (FCT-C6). The section below describes the commanding of the various block search variants by means of the PLC application HLI BlockSearch.

The PLC application is used to parameterise the block search and to observe the reaction of the NC kernel after starting the block search. The block search itself is activated when a block search type is selected in the PLC application, the required parameters are set and then a start of an NC program is requested. In the case of the example application, this is usually done via the Online tab of the corresponding channel in the SystemManager (TwinCAT 2) or the MOTION configuration (TwinCAT 3) by pressing the Start button there. For the purpose of simplification, the tab is referred to as Operation below

The block search is parameterised in the ADS program. There are no corresponding interfaces for this on the HLI. However, state data of the NC kernel can be retrieved via ADS and the HLI. State data can then be used to parameterise the block search via ADS communication. The handshake between PLC and NC kernel during the block search is processed by the corresponding control unit (CNC build >= 2800: gpCh[i].bahn_lc_control.block_search) on the HLI (see also [HLI//Block search], including diagrams on handshake).

The PLC application automatically acknowledges all technology functions (M, H, S, T) output by the NC kernel for channels 1 and 2 (see programme MAIN(), Fct: QuitChTechFunction() ).

The PLC application can be used to parameterise the block search and then to select whether the handshakes required to execute the function are carried out automatically by the PLC application (see state machine at the end of POU BlockSearch) or whether the user wants to command them step-by-step via the visualisation.

Visualisations are structured so that

• the data in the column under the designation "read command” are the currently effective parameters in the NC kernel for the block search and were read out by the ADS.
• the data in the column under "command to set” are the parameters that will become active the next time a block search is commanded, provided they have been transferred to the NC kernel by ADS after being entered in the visualisation field by pressing the set button.
• the state data displayed in the column "HLI act.value” can be transferred to the corresponding "command to set” field on the HLI by pressing the copy button. This is used to adopt the data on the HLI, e.g. after a program abort, in order to parameterise the block search.