Statement List (STL) - DCE FEL ČVUT v Praze

Counter Instructions
4.8 CD Counter Down
Format
CD
Address Data type Memory area Description
COUNTER C Counter, range
depends on CPU.
Description
CD decrements the count of the addressed counter by 1 when RLO
transitions from "0" to "1" and the count is greater than 0. When the count reaches its
lower limit of "0", decrementing stops. Additional transitions of RLO have no effect as
the counter will not count with negative values.
Status word
Example
BR CC 1 CC 0 OV OS OR STA RLO /FC
writes: - - - - - 0 - - 0
STL Explanation
L C#14 //Counter preset value.
A I 0.1 //Preset counter after detection of rising edge of I 0.1.
S C1 //Load counter 1 preset if enabled.
A I 0.0 //One count down per rising edge of I 0.0.
CD C1 //Decrement counter C1 by 1 when RL0 transitions from 0 to 1 depending on input
I 0.0.
AN C1 //Zero detection using the C1 bit.
= Q 0.0 //Q 0.0 = 1 if counter 1 value is zero.
Statement List (STL) for S7-300 and S7-400 Programming
4-8 A5E00706960-01