Synchronizing NC and PLC with FN 20: WAIT FOR

Application

With the FN 20: WAIT FOR function you can synchronize the NC and PLC during a program run. The NC stops machining until the condition that you have programmed in the FN 20: WAIT FOR block is fulfilled.

Description of function

 
Notice
Danger of collision!
Changes to the PLC can result in undesired behavior and serious errors (e.g., inoperability of the control). For this reason, access to the PLC is protected by password. This function provides HEIDENHAIN as well as your machine manufacturer and suppliers with the ability to communicate with the PLC from an NC program. It is not recommended for the machine operator or NC programmer to use this function. There is risk of collision during the execution of the function and during the subsequent machining!
  1. Only use the function in consultation with HEIDENHAIN, the machine manufacturer, or the supplier.
  2. Comply with the documentation from HEIDENHAIN, the machine manufacturer, and suppliers.

SYNC is used whenever you read, for example, system data via FN 18: SYSREAD that require synchronization with real time. The control stops the look-ahead calculation and executes the following NC block only when the NC program has actually reached that NC block.

Application example

32 FN 20: WAIT FOR SYNC

33 FN 18: SYSREAD Q1 = ID270 NR1 IDX1

In this example, you stop the internal pre-calculation of the control in order to determine the current position of the X axis.