Manual – IPOSplus®
189
14
Explanation of const.h and io.h / constb.h and iob.h
Compiler – Programming
The io.h header file defines macros that make it easier to query terminal levels. The fol-
lowing example illustrates this point.
The if statement queries terminal DI00, the /CONTROLLER INHIBIT terminal. If the ar-
gument of the if statement is zero, then the statements in the else part are processed
(assuming there is an else part). In this case, IPOS
plus®
variable H1 is set to zero or one
depending on the input level of terminal DI00. Note that it is impossible to query when
the terminal is set to 1 (DI00 == 1) because the macro supplies a binary evaluation. In
practical terms, it is possible to query for zero (DI00 == 0) or not equal to zero (DI00 != 0).
This program extract can be made clearer using the commands which have already
been explained. This is done by introducing additional symbolic identifiers.
The following appears in the variable window:
if( DI00 )
{
H1 = 1; // execute command block, if terminal DI00 has NOT level 0
}
else
{
H1 = 0; // execute command block, if terminal DI00 has level 0
}
#define controller_inhibit H1
#define HI 1
#define LO 0
if( DI00 )
{
controller_inhibit = 1; // execute command block, if terminal DI00 has NOT
//level 0
}
else
{
controller_inhibit = 0; // execute command block, if terminal DI00 has
//level 0
}
499400587
INFORMATION
Note that the io.h header file must be linked using the #include io.h command line be-
fore it can be used.
To Next Page