NORD Drivesystems BU0550 - Manual (Page 44)

PLC logic for NORD SK 54xE frequency inverters
44 BU 0550 GB-0813
3.5.1.1 CTD downward counter
With a rising flank on CD the counter of the function block CV is reduced by 1, as long as CV is greater than
-32768. If CV is less than or equal to 0, the output Q remains set to TRUE. Via LD the counter CV can be
set to the value saved in PV.
CD
LD
CV
Q
PV
Table 59 CTD downward counter
3.5.1.2 CTU upward counter
With a rising flank on CU, the counter of the function block CV is increased by 1. CV can count up to the
value 32767. As long as CV is greater than or equal to PV output Q remains set to TRUE. Via R the counter
CV can be reset to 0.
CU
R
CV
Q
PV
Table 60 CTU upward counter
VAR_INPUT VAR_OUTPUT
Input Explanation Type Output Explanation Type
CD Counter input BOOL Q TRUE, if CV <= 0 BOOL
LD Lad starting value BOOL CV Actual counter reading INT
PV Starting value INT
VAR_INPUT VAR_OUTPUT
Input Explanation Type Output Explanation Type
CU Counter input BOOL Q TRUE, if CV >= PV BOOL
R Reset: counter reading BOOL CV Actual counter reading INT
PV Max. counter value INT