Siemens simatic s7-400 FM 450-1, User Manual, Page: 80 / 130

Modes, settings, parameters and commands
8.12 Initiating a process interrupt
Counter module FM 450-1
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Manual, 02/2014, A5E03648739-02
8.10 Command: Open and close gate
Overview
The FM 450-1 counters have the following gates:
● A hardware gate (HW gate) which you can open and close level controlled or edge
controlled.
● A software gate (SW gate) which you can open and close via control bits in the user
program.
Selecting a gate
In the "Operating Mode" dialog (see section "Overview of modes, settings and commands
(Page 66)"), you specify which gate you want to use for the count process.
The following figures demonstrate the various possibilities for opening and closing the
FM°450-1 gates.
Level controlled opening and closing of the HW gate
The following figure shows the level controlled opening and closing of the HW gate of
counter°1.
Figure 8-4 Level controlled opening and closing of the HW gate of counter 1
If you set input 1I0 to 1 the count signals can reach counter 1 and are counted. If you reset
input 1I0 to 0, the door is closed. The count pulses are no longer counted, counter 1 stops.
If the gate of counter 1 is closed owing to overflow or underflow, you must first reset input 1I0
and apply a positive edge to input 1I0 to reopen the door.