CTD / CTDr
Function Block - Down counter.
Inputs
|
Input |
Data type |
Description |
|
CD |
BOOL |
Enable counting. Counter is decreased on each call when CD is TRUE. |
|
LOAD |
BOOL |
Re-load command. Counter is set to PV when called with LOAD to TRUE. |
|
PV |
DINT |
Programmed maximum value. |
Outputs
|
Output |
Data type |
Description |
|
Q |
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 CD input. Use R_TRIG or F_TRIG function block for counting pulses of CD input signal. In LD language, CD is the input rung. The output rung is the Q output.
CTUr, CTDr, CTUDr function blocks operate exactly as other counters, except that all boolean inputs (CU, CD, RESET, LOAD) have an implicit rising edge detection included. Not that these counters may be not supported on some target systems.
ST Language
MyCounter is a declared instance of CTD function block.
MyCounter (CD, LOAD, PV);
Q := MyCounter.Q;
CV := MyCounter.CV;
FBD Language
LD Language
CTD / CTDr |
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IEC 61131-3 Automation platform > Programming - Reference guide > Counters > CTD / CTDr |
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