Linking Files - HEIDENHAIN TNC 426 PB/M Technical Manual

7.14 Linking Files

7 – 174
You can store the source code of the PLC program in several files. To manage
these files, use the following commands:
n
USES
n
GLOBAL
n
EXTERN
These instructions must be located at the very beginning of your PLC program
– i.e., before the first PLC command (see PLC programming example). With
the USES instruction you link another file into the program. The GLOBAL
instruction supplies a label from its own file for an entry that can be used by
all other files. The EXTERN instruction provides a label that is defined in
another file and is identified there with GLOBAL. You can then call this label
from the active file. You can dramatically improve the transparency of your
program by dividing your source code by function into individual groups and
then save these groups in individual files. Each file can contain up to 1000
labels. You can link up to 60 files to one program. Each file can generate up to
64 KB of code. The permissible total length of the code is limited to 128 KB. If
you use more than one file, the main program must have the status flag "M"
in the directory. This is done in the RAM by using the PLC program function
"COMPILE" once and selecting the main program in the file window. In the
EPROM you must enter the option /M behind the main program in the linker
file for binary output.
HEIDENHAIN Technical Manual TNC 426, TNC 430