ISPSoft User Manual

Chapter 6 Symbols
• VAR-General symbol
The symbols of this class are for general operations only. The significance of a symbol of this
class depends on the data type of the symbol or the corresponding device.
• Latched symbol
Only AH500 series modules support the symbols of this class. Users can not declare the symbols
of this class in a function block. The function of the symbols of the VAR_RETAIN class is the
same as the function of the symbols of the VAR class. The difference between the symbols of the
VAR_RETAIN class and the symbols of the VAR class lies in the fact that the devices
automatically assigned to the symbols of the VAR_RETAIN class are latched devices. As a result,
the values of the symbols of this class will be retained after the PLC is disconnected.
*. Users can not assign a device to a symbol of this class. Besides, the data type can not be TIMER, COUNTER, or
STEP.
• VAR_INPUT-Symbol used as an input pin of a function block
A symbol of this class is used as an input pin of a function block, and is declared in the function
block. If a function block is called, the symbol of this class can receive the input value from the
caller. Besides, in a ladder diagram/function block diagram, the symbols of this class are put at
the left sides of the function blocks, and the pins which receive the values from the caller are
assigned to the symbols of this class.
• VAR_OUTPUT-Symbol used as an output pin of a function block
A symbol of this class is used as an output pin of a function block, and is declared in the function
block. After the execution of a function block is complete, the operation result will be sent to the
caller through the symbol of this class. Besides, in a ladder diagram/function block diagram, the
symbols of this class are put at the right sides of the function blocks, and the pins which sent the
operation results to the caller are assigned to the symbols of this class.
• VAR_IN_OUT-Symbol used as a feedback pin of a function block
A symbol of this class is used as a feedback pin of a function block, and is declared in the function
block. Please refer to the following example. When the function block is called, the caller sends
the value in D1 to DT_IO, which is a symbol of the VAR_IN_OUT class. After the operation comes
to an end, the final value of DT_IO is sent to D1. Besides, in a ladder diagram/function block
diagram, the symbols of this class are put at the right sides of the function blocks, and the blue
pins which connect to the caller are assigned to the symbols of this class.
6.1.3 Data Types
The data type of a symbol determines the significance of the value of symbol. Suppose there are
two symbols VAR_1 and VAR_2. The data type of VAR_1 is BOOL, and the data type of VAR_2 is
WORD. When VAR_1 and VAR_2 are used in a program, VAR_1 represents a contact, and VAR_1
represents a 16-bit device which can be involved in arithmetic or data transfer.
The data types supported by ISPSoft are listed below. Different models support different data types,
and the symbols which can be declared in a POU of the program type are different from the symbols
which can be declared in a POU of the function block type.
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