A function calculates a result according to the current value of its inputs. A function has no internal data and is not linked to declared instances. Block - Up/down counter.
Inputs
CU : BOOL Enable counting. Counter is increased on each call when CU is TRUE
CD : BOOL Enable counting. Counter is decreased on each call when CD is TRUE
RESET : BOOL Reset command. Counter is reset to 0 called with RESET to TRUE
LOAD : BOOL Re-load command. Counter is set to PV when called with LOAD to TRUE
PV : DINT Programmed maximum value
Outputs
QU : BOOL TRUE when counter is full, i.e. when CV = PV
QD : BOOL TRUE when counter is empty, i.e. when CV = 0
CV : DINT Current value of the counter
Remarks
- The counter is empty (CV = 0) when the application starts. The counter does not include a pulse detection for CU and CD inputs. Use R_TRIG or F_TRIG function blocks for counting pulses of CU or CD input signals. In FFLD language, CU is the input rung. The output rung is the QU output.
- CTUr, CTDr, CTUDr function blocks operate exactly as other counters, except
that all Boolean inputs (CU, CD, RESET, LOAD) have an implicit rising edgeA rising edge is the transition of a digital signal from low to high. It is also called positive edge
detection included.
ST Language
(* MyCounter is a declared instance of CTUD function block *)
MyCounter (CU, CD, RESET, LOAD, PV);
QU := MyCounter.QU;
QD := MyCounter.QD;
CV := MyCounter.CV;
FBD Language
FFLD Language
IL Language:
(* MyCounter is a declared instance of CTUD function block *)
Op1: CAL MyCounter (CU, CD, RESET, LOAD, PV)
FFLD MyCounter.QU
ST QU
FFLD MyCounter.QD
ST QD
FFLD MyCounter.CV
ST CV
See also
