PLC Programming

The Graphic Editors...
'Extras' 'Expand macro'
With this command, the selected macro is re-expanded and the elements contained in it are inserted
in the POU at the macro's location. The connections to the pins of the macro are again displayed as
connections to the in- or outputs of the elements. If the expansion of the macro can not occur at the
location of the macro box for lack of space, the macro is displaced to the right and down until enough
space is available.
Note:
If the project is saved under project version number 2.1, the macros will likewise all be expanded. All
macros will also be expanded before conversion into other languages.
'Extras' 'One macro level back', 'Extras' 'All macro levels back'
Symbols:
These commands are also available in the toolbar, as soon as a macro is opened for editing. If
macros are nested within one another, it is possible to switch to the next higher or to the highest
display level.
Feedback paths in CFC
Feedback paths can only be displayed directly in the continuous function chart editor and not in the
usual function block diagram editor. Here it should be observed that the output of a block always
carries an internal intermediate variable. The data type of the intermediate variable results, for
operators, from the largest data type of the inputs.
The data type of a constant is obtained from the smallest possible data type, that is the constant '1'
adopts the data type SINT. If now an addition with feedback and the constant '1' is executed, the first
input gives the data type SINT and the second is undefined because of the feedback. Thus the
intermediate variable is also of the type SINT. The value of the intermediate variable is only then
allocated to the output variable.
The diagram below shows an addition with feedback and an addition with a variable. The variables x
and y should be of the type INT here.
There are differences between the two additions:
The variable y can be initialised with a value which is not equal to zero but this is not the case for
intermediate variable for the left addition.
The intermediate variable for the left addition has the data type SINT while that on the right has the
data type INT. The variables x and y have different values after the 129 th call up. The variable x,
although it is of the type INT, contains the value 127 because the intermediate variable has gone into
overflow. The variable y contains the value 129, on the other hand.
CFC in Online mode
Monitoring:
The values for inputs and outputs are displayed within the input or output boxes. Constants are not
monitored. For non-boolean variables, the boxes are expanded to accommodated the values
displayed. For boolean connections, the variable name as well as the connection are displayed in blue
if the value is TRUE, otherwise they remain black.
Internal boolean connections are also displayed Online in blue in the TRUE state, otherwise black.
The value of internal non-boolean connections is displayed in a small box with rounded corners on the
output pin of the connection.
5-46 CoDeSys V2.3