CTDΒΆ

Provided by Standard Library.

Function block working as a decrementer.

Inputs:

CD : BOOL; With each rising edge at this input the counter value (CV) is decremented by 1 until 0 is reached.

LOAD : BOOL; If TRUE, CV will be set to the start value given by PV.

PV : WORD; start value for decrementing of CV.

Attention

Datatype WORD, which is used for PV in CODESYS, does not match the IEC standard, which for PV defines datatype INT.

Outputs:

Q : BOOL; gets TRUE as soon as CV is 0.

CV : WORD; gets decremented by 1, starting with PV until 0 is reached.

Declaration example:\ \ \ \

CTDInst : CTD ;

Example in IL:\ \ \ \

../_images/f106f23f1e8f77e8c0a8640e01947982

Example in FBD:\ \ \ \ :

../_images/467969ce1e8f773ac0a8640e01947982

Example in ST:\ \ \ \

CTDInst(CD:= VarBOOL1, LOAD:=VarBOOL2 , PV:= VarWORD1);

VarBOOL3 := CTDInst.Q ;

VarWORD2 := CTDInst.CV;