CTD block
Short summary
Name |
CTD |
→POU type |
|
Category |
|
Conform to →IEC-standard |
no restrictions |
Graphical interface |
|
Available since |
version 1.4.1 (for logi.CAD 3) |
Functionality
The block is a down-counter (for INT values).
If there is a positive →edge at input CD, the counter is activated and decrements the counter value by 1. If input LD is →turned on, the counter value is reset to the initial value entered at PV. If the counter value reaches or falls below 0, output Q is set to value TRUE (or an equivalent). The decrementing is stopped, if the lower limit of INT (= value -32,768) is reached. Output CV returns the current counter value of the block.
In-/outputs
|
Identifier |
Description |
|
Inputs: |
CD |
BOOL |
decrement in case of positive edge |
LD |
BOOL |
flag for reset to value of PV |
|
PV |
INT |
initial value for counting |
|
Outputs: |
Q |
BOOL |
flag showing whether value 0 is reached or not |
CV |
INT |
current counter value |
Input EN and output ENO are available when →calling the block. See "Execution control: EN, ENO" for information on input EN and output ENO.
Example for usage within ST-editor
PROGRAM Test
VAR
myCTD : CTD;
StartCounter : BOOL;
RestartCounter : BOOL;
out : BOOL;
counter : INT;
END_VAR
myCTD(CD := StartCounter, LD := RestartCounter, PV :=
10
, Q => out, CV => counter);
(* Instance of block
'CTD'
is called: The counter is activated, when
'StartCounter'
is
'TRUE'
. The value
for
counting is reset to
'10'
, when
'RestartCounter'
is
'TRUE'
. *)
(* Appropriate variables access the outputs. *)
END_PROGRAM
When creating your application within the ST-editor, enter a call of a block by typing the text as requested by the syntax or use Content Assist.