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AT: Direct representation of a variable.
FUNCTION BLOCK: It is a function that needs an instance.
CONFIGURATION: It is the organization of a software application in a higher level. It may contain Resources within a Configuration.
FUNCTION: It is a block responsible for executing a certain behavior or an action based on possible parameters (VAR_IN, VAR_IN_OUT, VAR_OUT).
INSTANCE: Memory area taken according to the Functional Block.
LD (Ladder Diagram): Graphical language based on the electric diagrams (interconnected contacts and coils), according to the power flow between the elements.
OVERFLOW: It occurs when the result of a mathematical calculation exceeds the limits permitted for the result data type.
POU: Program Organization Unit. It may be: Program, Functional Block or Function.
PROGRAM: It is the logical grouping of all programming elements and constructions necessary for processing the signals required to control a machine or process.
RESOURCE: They consist of any element with processing capacity responsible for executing the programs.
SCAN: Scan cycle of a program.
STACK: Stack of the Ladder program. It is the memory area used to perform the Program Logics.
TASK: Responsible for the execution of programs, in a periodical or triggered way, with trigger by event.
DATATYPE: It informs the compiler the space taken by a variable and its respective format (to the Blocks).
VARIABLE: It consists of a memory position able to withhold and represent a value or expression. It may have scope:
| • | Location: whose automatic position is calculated by the compiler. |
| • | Global: located in a determined memory area with digital inputs and outputs, it may be accessed at any point of the Configuration. |
The variable may be:
| • | Retentive: it stores the value after powering down the device; |
| • | Volatile: it begins with the value contained in the initial value field after the powering down of the device; |
| • | Constant: it does not allow the modification of its content. |
VAR: Variables for internal use of a User’s Block (USERFB). Equivalent to a variable of Local scope.
VAR_IN: Input argument of a User’s Block (USERFB). Variables configured in this field will be only read on the USERFB.
VAR_IN_OUT: Input and output argument of a User’s Block (USERFB). It will not allow CONSTANT variables, PHYSICAL INPUTS (%I_), NETWORK INPUTS (%I_) or READING SYSTEM MARKERS (%S_), because they will be read at the beginning of the USERFB and will be updated with new values (written) at the end of the USERFB.
VAR_OUT: Output argument of a User’s Block (USERFB). It will not allow CONSTANT variables, PHYSICAL INPUTS (%I_), NETWORK INPUTS (%I_) or READING SYSTEM MARKERS (%S_), because they will be updated with new values (written) at the end of the USERFB.
WATCHDOG: It is a way provided by the manufacturer to perform specific actions if the integrity of the system is violated.