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Designing a Sequential Function Chart 143 Transition Tag Each transition uses a BOOL tag to represent the true or false state of the transition. If the transition is: The value is: And: true 1 The SFC goes to the next step. false 0 The SFC continues to execute the current step. How Do You Want to Program the Transition? To program the transition, you have these options: If you want to: Then: enter the conditions as an expression in Structured Text Use a BOOL Expression enter the conditions as instructions in another routine Call a Subroutine use the same logic for multiple transitions Use a BOOL Expression The simplest way to program the transition is to enter the conditions as a BOOL expression in Structured Text. A BOOL expression uses bool tags, relational operators, and logical operators to compare values or check if conditions are true or false. For example, tag1>65. Here are some examples of BOOL expressions. bool_tag_a bool_tag_a & bool_tag_b dint_tag_a > 8 Publication 1756-PM001I-EN-P - January 2007
