ISPSoft User Manual

Chapter 7 Function Block
The principles of using a symbol whose data type is POINTER, T_POINTER, C_POINTER, or
HC_POINTER are as follows.
1. Only AH500 series CPU modules support a symbol whose data type is POINTER, T_POINTER,
C_POINTER, or HC_POINTER.
2. The symbols whose data types are POINTER can only be declared in the function blocks in a
project, and they must be symbols of VAR_IN_OUT class.
3. The pointers and the restrictions are described below.
Pointer
Restriction
Maximum 16 symbols whose data types are POINTER can be
number declared in a function block.
General pointer
Symbol whose data type is
POINTER
Reference WORD/DWORD/LWORD/INT/DINT/LINT, data register, link
register, or X/Y device (e.g. X0/Y0)
Maximum 8 symbols whose data types are T_POINTER can be
Pointer for a timer
number declared in a function block.
T_POINTER
Reference Timer or symbol whose data type is TIMER
Maximum 8 symbols whose data types are C_POINTER can be
Pointer for a counter
number declared in a function block.
C_POINTER
Reference Counter or symbol whose data type is COUNTER
Pointer for a
Maximum 8 symbols whose data types are HC_POINTER can be
high-speed counter
number declared in a function block.
32-bit counter or symbol whose data type is COUNTER and
HC_POINTER Reference
to which a 32-bit counter is assigned
• Example of using a symbol whose data type is POINTER
The function block FB0 has three input pins. The data types and the classes are in the red
frame in the local symbol table below. D0, D1, and D2 in the POU (caller) are assigned to the
three pins. (The initial values in D0, D1, and D2 are 0.) The execution of the program is as
follows.
‣ D0 is assigned to VAR_IN. VAR_IN is a symbol of the VAR_INPUT class, and the data type
of VAR_IN is WORD. When the function block is called, the present value in D0 is copied
into VAR_IN. After the operation inside the function block is performed, 4 will be added to
the value of VAE_IN. The operation result does not affect D0, and therefore the value in D0
is always 0.
‣ D1 is assigned to VAR_IO. VAR_IO is a symbol of the VAR_IN_OUT class, and the data
type of VAR_IO is WORD. When the function block is called, the present value in D1 is
copied into VAR_IO. After the operation inside the function block is performed, 4 is added to
the value of VAR_IO. Owing to the fact that VAR_IO is a symbol of the VAR_IN_OUT class,
the value of VAR_IO is copied into D1 after the function block is executed. The value sent
from D1 to VAR_IO is an accumulated value. The value in D1 accumulates during the
execution of the function block.
‣ D2 is assigned to pVAR. Owing to the fact that the data type of pVAR is POINTER, the sum
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