Function Description - Siemens SIMATIC CM35 Manual

Timer Operating Mode
7.1

Function Description

Switch- -on times
Start and stop
timers
Controlling the
outputs
Monitoring the
outputs
7-2
Timer mode can be used to implement precisely defined switch- - on times for
the 8 digital outputs of the counter module.
Times from 10 milliseconds to 278 minutes can be specified seperately for
the switch- - on times.
The timers are started by the user program, thus setting the related digital
outputs.
If no parameter values for time base and factor are available when a timer is
started, these values are processed with 1 as the default value.
The related digital output is switched off after the parameterized time
expires.
A started timer can be terminated by transferring the control word with a ²0²
for the applicable channel in the start/stop byte. This resets the digital output
and the internal counter.
The end of the switch- - on time is indicated by a hardware interrupt. This can
be acquired by the user program to trigger additional processing (e.g., to
position the next container in proportioning systems/filling systems).
A timer must be stopped before the user program can execute a new start.
This can be done after the ²timer expired² hardware interrupt or after a time
calculated by the user program which is with certainty longer than the run
time of the timer.
The digital outputs of the timer can also be controlled by writing the DO byte
(e.g., for continuous switch- - on during washing procedures). The user pro-
gram must ensure that the timer channels cannot be manipulated
(see chapter 7.4).
The module can monitor the switching status of its outputs. To do this, the
digital outputs must be wired to the digital inputs. The firmware cyclically
compares the status of the digital outputs with the status of the digital inputs
and generates a hardware interrupt when required by the parameterization
(e.g., timer failure). The interrupt can be output as a group interrupt or as a
selective interrupt (i.e., channel- - specific).
CM35 Counter Module
(4) J31069-D0416-U001-A5-7618