Siemens SIMATIC S7-200 System Manual page 137

Phase A
Clock
Phase B
Clock
Counter Current
Value
0
Figure 6-26 Operation Example of Modes 9, 10, or 11 (Quadrature 4x Mode)
Reset and Start Operation
The operation of the reset and start inputs shown in Figure 6-27 applies to all modes that use
reset and start inputs. In the diagrams for the reset and start inputs, both reset and start are
shown with the active state programmed to a high level.
Example with Reset
and without Start
Reset 1
(Active High)
0
+2,147,483,647
Counter
0
Current Value
- -2,147,483,648
Counter value is somewhere in this range.
Figure 6-27 Operation Examples Using Reset with and without Start
Current value loaded to 0, preset loaded to 9, initial counting direction set to up.
Counter enable bit set to enabled.
PV=CV interrupt generated
1
0
1
0
10
9
8
7
6
5
4
3
2
1
Reset interrupt
generated
S7-200 Instruction Set
12
11
Example with Reset
Counter
and Start
disabled
Start 1
(Active High)
0
Reset 1
(Active High)
0
+2,147,483,647
Current
Counter
0
value
Current Value
frozen
- -2,147,483,648
Counter value is somewhere in this range.
Chapter 6
Direction Changed
interrupt generated
PV=CV
interrupt generated
11
10
9
8
7
6
Reset interrupt Reset interrupt
generated generated
Counter Counter
Counter
disabled enabled
enabled
Current
value
frozen
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