Attention
IronPLC can only run very simple programs. The steps described are accurate but many language features are not yet supported.
CTD¶
Count-down counter. Decrements the counter value CV on each rising edge of
CD. Output Q becomes TRUE when CV reaches or falls below zero.
IEC 61131-3 |
Section 2.5.2.3.4 |
Support |
Not yet supported |
Inputs¶
Name |
Type |
Description |
|---|---|---|
|
|
Count-down input (decrements on rising edge) |
|
|
Load input (loads PV into CV) |
|
|
Preset value |
Outputs¶
Name |
Type |
Description |
|---|---|---|
|
|
Counter output (TRUE when CV <= 0) |
|
|
Current counter value |
Behavior¶
On each rising edge of CD, the counter value CV is decremented by one.
When LD is TRUE, the preset value PV is loaded into CV. The
output Q is TRUE when CV is less than or equal to zero.
Example¶
VAR
counter1 : CTD;
count_pulse : BOOL;
load : BOOL;
done : BOOL;
END_VAR
counter1(CD := count_pulse, LD := load, PV := 10);
done := counter1.Q;