Standard Contact Bit Logic

Inputs/Outputs Operands Data Types
bit (LAD, STL) I, Q, M, SM, T, C, V, S, L BOOL
Input (FBD) I, Q, M, SM, T, C, V, S, L, Power Flow BOOL
Output (FBD) I, Q, M, SM, T, C, V, S, L, Power Flow BOOL

Memory Ranges ENO Errors Instruction Support for S7-200 CPUs SIMATIC/International Mnemonics
These instructions obtain the referenced value from memory or from the process image register if the data type is I or Q.

The Normally Open contact is closed (on) when the bit is equal to 1.

The Normally Closed contact is closed (on) when the bit is equal to 0.

In LAD, normally open and normally closed instructions are represented by contacts.

In FBD, normally open instructions are represented by AND/OR boxes. These instructions can be used to manipulate Boolean signals in the same manner as ladder contacts. Normally closed instructions are also represented by boxes. A normally closed instruction is constructed by placing the negation symbol on the stem of the input signal.

In STL, the normally open contact is represented by the Load, AND, and OR instructions. These instructions Load, AND, or OR the bit value of the address bit to the top of the stack.

In STL, the normally closed contact is represented by the Load NOT, AND NOT, and OR NOT instructions. These instructions Load, AND, or OR the logical NOT of the bit value of the address bit to the top of the stack.


Example