Cooperative Multitasking; Starting A Parallel Process (Spawn) - HEIDENHAIN iTNC 530 HSCI Technical Manual

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9.12 Cooperative multitasking

You can run several processes in the PLC with cooperative multitasking.

Unlike genuine multitasking, with cooperative multitasking information and

tasks are exchanged only at places that you define. Cooperative multitasking

permits up to eight parallel PLC processes and the submit queue. In a program

that you have started with SUBM, you can use commands for changing tasks

and controlling events (Module 926x). You should additionally insert a task

change between the individual jobs in the submit queue, so that the iTNC can

execute parallel processes by the end of a job at the latest. The cyclic PLC

main program does not participate in cooperative multitasking, but interrupts

a submit job and the parallel processes at whatever their current stage is.

SPAWN <label>

In the specified double word, the iTNC returns the identifier (, see page 1831).

If no process could be started, the iTNC returns the value –1. You can call the

spawn command only in a submit job or in another spawn process (maximum

of 16 parallel processes are permitted). If a process ends with EM, the iTNC

removes it from the memory to provide space.

9.12 Cooperative multitasking