Block search

Block search on/off, handshake with PLC

Description

At every block search on/off request, the CNC initiates a handshake with the PLC;

As long as the request element has the value TRUE, the PLC is notified of every change in block search mode.

Data type

LC_CONTROL_BOOL_UNIT, see description Control Unit

Special features

Consumption data item

Access

If an NC program starts with the block search mode activated, the CNC set the CNC signal to TRUE and waits for the PLC signal indicating that it is ready for block search.

When the PLC has executed the necessary actions to prepare for block search, it notifies this to the CNC by setting the PLC signal to TRUE.

After this signal, the NC program can be processed in block search mode. This takes place by the “Continue motion” or “Program start” commands.

If the re-engagement position is reached while the NC program is processed, the CNC signals this by setting the CNC signal to FALSE.

The PLC detects this, completes its preparations for operation with real axis motions and then sets the PLC signal to FALSE.

ST path

gpCh[channel_idx]^.bahn_lc_control.block_search

CNC signal

ST element

.command_r

Signal flow

CNC → PLC

Data type

BOOL

Value range

[TRUE = NC program was started in block search mode, FLASE = Block search is disabled]

PLC signal

ST element

.state_w

Signal flow

PLC → CNC

Data type

BOOL

Value range

[TRUE = PLC acknowledged the notification about block search activation, FALSE = PLC acknowledged the notification of block search deactivation]

Requirement

ST element

.enable_w

Data type

BOOL

Value range

[TRUE = PLC wants to be notified about activation of block search, FALSE]