L9_DCTR: Down Counter
(Original Document)
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Function Description
The L9_DCTR function block counts control input transitions - from OFF to ON - down from a counter PRESET value to 0.
The downward counting operation begins when the input to the ENABLE pin is turned ON. The ACCUM value decrements while the RUN input remains ON. When the RUN input turns OFF, the ACCUM value is reset to the counter PRESET value.
L9_DCTR can activate 1 of 2 outputs. The EQ_ZERO output turns ON if the ACCUM value has decremented to 0; the GR_ZERO output turns ON when the block is solved and the value of ACCUM is greater than 0.
NOTE: The ACCUM value is also decremented in case of a PLC Start or in case of Power ON.
Representation
Parameters
Input Pin
Name
Data Type
Address Range
Meaning
Top
ENABLE
BOOL
–
OFF to ON initiates the count if the RUN button is also ON.
Bottom
RUN
BOOL
–
OFF resets the counter to the PRESET value; ON lets the counter execute when ENABLE turns ON.
Node
Node Type
Name
Data Type
Address Range
Meaning
Top
IN
PRESET
UINT
%IW, %MW
The preset value from which the counter counts down. Can be displayed as an integer constant, or can be stored in a variable located in a %IW input word or a %MW memory word or an unlocated word. Valid range: 1 to 65,535.
Bottom
IN/OUT
ACCUM
UINT
%MW
The accumulated count. Decrements down from the preset value by a value of 1 each time the top input transitions from OFF to ON, until this value reaches 0. A variable tied to this pin can be located in a %MW memory word or an unlocated UINT word.
Output Pin
Name
Data Type
Address Range
Meaning
Top
EQ_ZERO
BOOL
–
ON indicates the accumulated count equals 0.
Bottom
GR_ZERO
BOOL
–
ON indicates the accumulated count is greater than 0.