ISPSoft User Manual

ISPSoft User Manual
7.3 Using a Function Block
7.3.1 Basic Specifications for the Function Blocks
The specifications for the function blocks in ISPSoft are shown below. When users use function
blocks, they have to make sure that the operation conforms to the specifications in the table.
Otherwise, an error occurs when the program is compiled or executed.
• Specifications for the function blocks
Number of
function block
definitions
Number of
function block
instances
Size of a function
block
Number of layers
AH500: The number of function block definitions which produce the instances
can not be larger than 1024.
DVP: The number of function block definitions depends on the number of P
devices available. (One function block instance occupies one P
device.)
AH500: The maximum number of memory blocks depends on the model
selected. (Please refer to appendix B.)
DVP: The number of function block instances depends on the number of P
devices available. (One function block instance occupies one P
device.)
AH500: The size of a memory block is 4096 words.
DVP: The size of a function block depends on the devices assigned to the
function block
A function block can calls another function block, and 32 layers of function
blocks at most can be called.
• Note
‣ The pins of a function block must be assigned operands. The operands can be device
addresses or symbols. If the class of a symbol is VAR_INPUT, the operand assigned to the
symbol can be a constant.
‣ An inferior function block can not call the superior function block, and a function block can not
call itself.
‣ If a function block is exported, the definition of the function block is exported, but the definitions
of the inferior function blocks and the global symbols used are not exported.
‣ The En pins of the function blocks in ladder diagrams, sequential function charts, function block
diagrams, and instruction lists must be connected to contacts. However, the En pins of the
function blocks in structured texts do not have to be connected to contacts.
‣ The programming languages which support the creation of function blocks include ladder
diagrams, instruction lists, structured texts, and function block diagrams. Sequential function
charts do not support the creation of function blocks.
‣ The programming languages which support the calling of function blocks include ladder
diagrams, instruction lists, structured texts, and function block diagrams. Users can also use
function blocks in the actions in sequential function charts.
‣ Users can modify function block definitions, but they can not modify function block instances.
(Please refer to section 7.3.4.)
‣ If the modification of a function block definition in the online mode results in the abnormal
representation of the function block in the superior POU, users have to disable the online
editing function, delete the abnormal representation of the function block, and add the normal
representation of the function block. After the normal representation of the function block is
added, the program can be compiled and downloaded. (Please refer to section 7.3.4 for more
information.)
‣ If a jump instruction is used in a function block, the jump destination must be in the same
function block, and can not be outside the function block or in the inferior function block.
‣ Users can not declare symbols whose data types are TIMER and symbols whose data types
are COUNTER in the function blocks in a project for an AH500 series CPU module, but they
can declare symbols whose data types are POINTER, symbols whose data types are
T_POINTER, symbols whose data types are C_POINTER, and symbols whose data types are
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