Siemens SIMATIC S7-300 FM 350-1 Manual page 115

Figure 7-19
Boundary conditions for the behavior of the digital outputs
If you assign the behavior of the digital outputs, you must observe the following boundary
conditions.
Table 7- 23 Boundary Conditions for the Behavior of the Digital Outputs
If...
... ...You want to parameterize an output "Active from
comparison value to overflow or underflow"
... ...You want to parameterize an output "Active from
comparison value to overflow"
... ...You want to parameterize an output "Active from
comparison value to underflow"
... ...You want to parameterize an output "Active on
reaching the comparison value for pulse duration
(up)"
... ...You want to parameterize an output "Active on
reaching the comparison value for pulse duration
(down)"
Default Setting of the Outputs
The outputs are disabled in the default setting.
FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01
Reactions of an output for a pulse duration = 0 ms
Then...
... ...You must ensure that the time between these events is
greater than the minimum switching time of the outputs (switching
time: 300 µs); otherwise, the control pulses at the outputs are lost.
If the counter status reaches the relevant comparison value again
while the output is still active, no new pulse is initiated. A further
pulse can only be initiated when the output is no longer active.
... ...you must not enable a hardware interrupt on "Reaching the
relevant comparison value (up/down)".
... ...you must not enable a hardware interrupt on "Reaching the
relevant comparison value (up/down)".
... ...You must not enable a hardware interrupt on "Reaching the
relevant comparison value (down)".
... ...You must not enable a hardware interrupt on "Reaching the
relevant comparison value (up)".
Operating Modes, parameters and commands
7.3 Count modes
115