PLC Programming

The Standard.lib library
CTUD
Function Block Incrementer/Decrementer
The input variables CU, CD, RESET, LOAD as well as the output variables QU and QD are type
BOOL, PV and CV are type INT.
If RESET is valid, the counter variable CV will be initialized with 0. If LOAD is valid, CV will be
initialized with PV.
If CU has a rising edge from FALSE to TRUE, CV will be raised by 1. If CD has a rising edge from
FALSE to TRUE, CV will be lowered by 1 provided this does not cause the value to fall below 0.
QU returns TRUE when CV has become greater than or equal to PV.
QD returns TRUE when CV has become equal to 0.
Declaration example:
CTUDInst : CUTD ;
Example in IL:
CAL
LD
ST
LD
ST
LD
ST
CTUDInst(CU := VarBOOL2, RESET := VarBOOL3, LOAD := VarBOOL4,
PV := VarINT1)
CTUDInst.QU
VarBOOL5
CTUDInst.QD
VarBOOL6
CTUDInst.CV
VarINT2
Example in FBD:
Example in ST:
CTUDInst(CU := VarBOOL1, CU:= VarBOOL2, RESET := VarBOOL3, LOAD:=VarBOOL4 , PV:=
VarINT1);
VarBOOL5 := CTUDInst.QU ;
VarBOOL6 := CTUDInst.QD ;
VarINT2 := CTUDInst.CV;
10.16.5 Timer...
TP
The function blockTimer is a trigger. TP(IN, PT, Q, ET) means:
IN and PT are input variables of the BOOL and TIME types respectively. Q and ET are output
variables of the BOOL and TIME types respectively. If IN is FALSE, Q is FALSE and ET is 0.
10-48 CoDeSys V2.3