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Function blocks: they are a general routine (software) executed in different programs.
It is possible to “call” the FB in every part of the program; in this way is
not necessary to write the same program a lot of time. Besides you can
save them in the library and also protect them with a password.
These FB can be developed by ISaGRAF, Dixell and from third party.
Variables: they are values that can change during the execution of the program.
For each variable we can define:
• NAME: it is the name of the variable
• COMMENT: the description of the variable (free field)
• GROUP: you can organize the variables in different groups.
• INIT VALUE: it is the value when the program starts.
• TYPE:
Bool: can assume the value 0=FALSE, 1=TRUE
Dint: can assume values from -2147483648 to +2147483647
Real: can assume floating point values
String: contain character strings (with specified the length)
Time: contain values used in time expression
Any: function block
• DIMENSION: specifies the dimension of the array of variables
• RETAIN:
Yes: the value will be saved in not volatile memory
No: the value will not be saved
• ATTRIBUTE:
Read: the application can read the value but not change it
Write: the application can modify the value but not read it
Free: the application can read and modify the value
• DIRECTION:
Input: the application reads the value from field
Output: the application writes the value to the field
Internal: any other variables
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