Introduction

Alternative sequences and parallel sequences are differentiated in SFC:

• Alternative sequence

  The alternative sequence offers the option to program conditional branches in the control flow of the SFC structure, see also Alternative Branches and Alternative Joints in the Reference manual.

  Alternative sequences consist of:

  • Alternative branch

    With alternative branches, as many transitions follow a step under the horizontal line as there are different processes.

  • Alternative joint

    All alternative branches are linked to a single branch using alternative joints or jumps where they are then continued to be processed.

• Parallel sequence

  With parallel sequences the connection of an individual transition leads to the parallel activation of several (maximum 32) steps (branches). After this activation, the individual branches are processed independently from one another, see also Parallel Branches and Parallel Joints in the Reference manual.

  Parallel sequences consist of:

  • Parallel branch

    With parallel branches, as many transitions follow a step under the horizontal line as there are parallel processes.

  • Parallel joint

    In accordance to IEC 61131-1, all parallel branches are joined at their ends by a common parallel joint. The transition to a parallel connection is evaluated when all previous steps of the transition are set.

    If a parallel branch is combined using an alternative joint, this is only possible with Multi-Token-Operation, see also dialog box Tools > Project Settings tab Language extensions area Sequential control (SFC).

Selecting Branches and Joints

Selecting Branches and Joints: