HEIDENHAIN MANUALplus 620 Technical Manual page 1660

8.14.3 Program structure
1660
To make it easier to maintain and expand your PLC program, you should give
it a modular structure. Modular means that you write a separate program
module for each function. You can then call the individual modules from the
main program. You should interrogate improper functioning of the machine in
the PLC program and indicate such malfunctions on the screen with plain-
language error messages.
Module 9019 Size of the processing stack
To debug functions, you can use Module 9019 to interrogate the contents of
the processing stack. The function answers with the number of the bytes that
lie on the processing stack of the PLC at the moment. If the processing stack
is empty, the PLC run-time system returns the value zero. A byte, word or
double word occupies four bytes on the stack; a marker, input, output, timer
or counter occupies two bytes.
Call:
CM 9019
PL B/W/D <Number of bytes on processing stack>
HEIDENHAIN Technical Manual MANUALplus 620