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Function Block Specifications
Section 2-1
(2) AT settings can be used only with the CIO (Core I/O Area), A (Auxiliary
Area), D (Data Memory Area), E (Extended Memory Area, H (Holding
Relay Area), W (Internal Relay Area).
The AT property cannot be set in the following memory areas:
• Index Register and Data Register Areas (directly/indirectly specified)
• Indirectly specified DM/EM (: binary mode, *:BCD mode)
(3) AT settings can be used for the following allocations.
• Addresses for Basic I/O Units, CPU Bus Units, or Special I/O Units
• Auxiliary Area bits not registered as external variables in advance
• PLC addresses for other nodes in the network
• Instruction operands specifying the beginning word (or end word) of
multiple words.
Example:
If the READ DATA FILE instruction (FREAD) is being used in the function
block definition and it is necessary to check the File Memory Operation Flag
(A34313), use an internal variable and specify the flag’s address in the AT set-
ting.
Register an internal variable, select the AT setting option, and specify A34313
as the address. The status of the File Memory Operation Flag can be checked
through this internal variable.
When the AT setting is used, the function block loses its flexibility. This func-
tion should thus be used only when necessary.
Array Setting
With internal variables, a variable can be defined as an array.
Note
Only one-dimensional arrays are supported by the CX-Programmer.
With the array setting, a large number of variables with the same properties
can be used by registering just one variable.
• An array can have from 1 to 32,000 array elements.
• The array setting can be set for internal variables only.
• Any data type can be specified for an array variable, as long as it is an
internal variable.
• When entering an array variable name in the algorithm of a function block
definition, enter the array index number in square brackets after the vari-
able name. The following three methods can be used to specify the index.
(In this case the array variable is a[].)
• Directly with numbers (for ladder or ST language programming)
Example: a[2]
• With a variable (for ladder or ST language programming)
Example: a[n], where n is a variable
Address A34313 is allocated to a
boolean internal variable named
NOW_CARD_ACCESS.
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