Parallel branching allows two or more states to occur simultaneously if a single transition condition is met. The difference between them lies in the placement of transition conditions. SFC allows branching of the paths in two ways: selective and parallel. Think of the vertical lines between steps as paths from the previous state to the next state. Links between steps and transitions which are direct and with direction.Transitions with associated logic conditions.Only if OUT 1 and IN 2 occur will OUT 2 activate. Only if IN 1 occurs will OUT 1 also activate. The first rung of the ladder is equivalent to Step 1. A step should always separate two transition conditions.Įvery SFC can be represented by an equivalent ladder logic.There should be a transition condition between two steps.Two conditions must be followed for every SFC: Outputs are represented as rectangular boxes linked horizontally to their respective state. Sometimes transition conditions can be denoted by a much smaller rectangle between the larger states.Īfter a step is completed, the process moves on to the next state only if the transition condition(s) is also satisfied.Įach of the states also has corresponding outputs. The horizontal lines between boxes represent transition conditions.
Two states are connected with a vertical line. The first box represents the start of the operation. Figure 1 below shows the general diagram for the sequential function chart. There is a transition condition between steps. A vertical straight line connects the different steps, and each step has a corresponding output.
In SFC programming, states or steps are represented by rectangular boxes. The terms ‘steps’ and ‘state’ represent the same concept in SFC programming. When one step is over, the next automatically begins. When a program is selected on the washing machine, it has multiple steps that come one after the other. In this programming language, the operations are described as separate steps that are sequentially connected.Īn example of this sequential connection can be seen in the operation of a washing machine.
SFC programming language makes it easier to visualize and design complex sequential systems. Sequential controls include processing sequential and parallel operations that are discrete in terms of time or events, mainly to control complex process sequences. SFC programming’s advantage is its ability to help the engineer break down large and complex processes into smaller pieces that are easy to understand. SFCs are commonly used and easier to represent in scenarios where there are multiple states of operations. SFCs are not text-based programming languages, but rather visual programming languages, similar to the flow charts for computer science algorithms.
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