Siemens SIMATIC S5 Manual page 129

Programming the IP 265 with COM 265
Counter operation
Up counter "CU":
Each change from "0" to "1" at the CU input
increments the count by 1. The counter is not
incremented once it has reached the upper limit value
(999).
Down counter "CD":
Each change from "0" to "1" at the CD input
decrements the count by 1. The counter is not de-
cremented once it has reached the lower limit value
(0).
Example: The counter is set to 7 when input 0.1 is
set. Output 0.5 is now "1". Each time
input 0.0 is set (down counting), the count
is decremented by 1. The output is set to
"0" when the count is "0".
Possible options for counter functions:
• The following inputs and outputs for counter functions may be inverted: S, R, CU, CD, Q.
9-24
Table 9-11. Counter Operations
CSF (example)
CU/D
> CU
> CD
I 0.0
CV
KC 7
> S
I 0.1 BI
R Q
Timing diagram
1
0
1
0
7
0
1
0
Set Set
EWA 4NEB 812 6130-02a
IP 265
Q 0.5
I 0.0
I 0.1
Count
Q 0.5
Time