Automatic control function programming manual ladder language

Return code
If OK
Value returned by the %SP module called using function return ().
Not significant if the called module does not return a value.
Example of Use of sp(), cpyarg(), return()
General Purpose Functions
Exchange of arguments during a call to an %SP module
Calling module (%TS, %TF or %SP):
%M100.W = sp(33, 10, %M20.B + %M30.B);
Module called %SP33:
Arguments 10 and (%M20.B + %M30.B) are extended to 32 bits
and stored on the stack. The call to %SP33 is then made.
cpyarg(M200.&, 2); Copies the two parameters of the call to local memory starting from
%M200. The value 10 is stored in %M200.L and the result of the
expression (%M20.B + %M30.B) is stored in %M204.L.
return(%V100.W+25);
Recommendation
Return to calling module. The value of expression %V100.W + 25
is loaded in %M100.W.
Passing arguments avoids inter-module communication via common variables.
This programming concept is recommended because it keeps the modules independent, thereby facilitating their
reuse in other applications.
6.26.2 Call an %SP Module with %Y Local Variables spy
Syntax
spy(moduleno {, argn}6 ...)
moduleno: Number of the %SP module to be called.
argn: Optional argument.
Calls an %SP module (%SP0 to %SP255) with creation of 128 %Y local variables and passes it any arguments via
the stack.
Operation
The module number must be between 0 (call to %SP0) and 255 (call to %SP255).
128 %Y local variables are created in the stack. These variables are deleted on return to the calling programme.
The arguments are extended on 32 bits and stored on the stack except moduleno which is not stacked.
The total number of arguments (including moduleno) must not exceed NBM_PARAM (i.e. 7).
spy(..) and %Y variables are used to write relocatable, reentrant %SP modules.
REMARK The sample programme L_E_VAR.MCH available under PLCTOOL illustrates instruction
spy().
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