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Function Block Specifications
Section 2-1
ENO (Enable Output) Variable
The ENO variable is created as the default output variable. The ENO output
variable will be turned ON when the instance is called. The user can change
this value. The ENO output variable can be used as a flag to check whether or
not instance execution has been completed normally.
Input-Output Variables
Input-output variables use addresses to pass data to and from a function
block instance. An input-output variable is displayed on both the left and right
side of the instance. The value of the input-output variable immediately after
the instance is executed is not stored in the addresses internally allocated to
the input-output variable by the system, but rather the value is stored in the
address (and following addresses depending on the data size) of the parame-
ter used to pass data to and from the input-output variable.
Note Input-output variables are specified a CX-Programmer variable table by
selecting “In Out” for the variable usage.
■ Internal Variables
Internal variables are used within an instance. These variables are hidden
within each instance. They cannot be referenced from outside of the instance
and are not displayed in the instance.
The values of internal variables are retained until the next time the instance is
executed (i.e., when EN turns OFF, the value of the internal variable is
retained). Consequently, even if instances of the same function block defini-
tion are executed with the same I/O parameters, the result will not necessarily
be the same.
Example:
The internal variable tim_a in instance Pulse_2sON_1sOFF is different from
internal variable tim_a in instance Pulse_4sON_1sOFF, so the instances can-
not reference and will not affect each other’s tim_a value.
1.0
FB
EN ENO
CAL CAL
P_ON
D200
D200
Address D200 is passed to the input-output variable CAL.
Inside the function block, the specified data size of I/O
memory starting from D200 is processed, and changes are
thus passed outside the function block instance.
P_On
1.0
&10
CLOCK PULSE
EN ENO
ON_TIME
OFF_TIME
&20
Pulse_2sON_1sOFF
P_On
1.1
&10
CLOCK PULSE
EN ENO
ON_TIME
OFF_TIME
&40
Pulse_4sON_1sOFF
tim_a TIMER
tim_b TIMER
ON_TIME INT
OFF_TIME INT
Variable table
Name
Internal
Internal
Input
Input
Data type
Usage
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