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ISPSoft User Manual

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Chapter 7 Function Block<br />

*. SM400 is a special auxiliary relay in an AH500 series CPU module. It is ON when the CPU module is<br />

powered.<br />

7.2.5 Function Block Definition and Function Block Instance<br />

The definition of a function block and an example of a function block are important concepts. Please<br />

refer to the following example. Whenever the superior POU (caller) is executed, the value of V1_IN<br />

is sent to the function block RIPPLE_FILTER. After the value sent to the function block this time is<br />

compared with the value recorded last time, the final operation result will be sent to V1_OUT in the<br />

superior POU. In order to record the operation result, a local symbol in which the operation result<br />

can be stored is declared in the function block. When the program is compiled, the system assigns a<br />

substantial memory block to this local symbol.<br />

7-11

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