Siemens Simatic S7-200 System Manual page 52

S7-200 Programmable Controller System Manual
The S7-200 Allows You to Allocate Processing Time for Communications
Tasks
You can configure a percentage of the scan cycle to be dedicated for processing the communications
requests that are associated with a RUN mode edit compilation or execution status. (Run mode edit and
execution status are options provided by STEP 7–Micro/WIN to make debugging your program easier.) As
you increase the percentage of time that is dedicated to processing communications requests, you
increase the scan time, which makes your control process run more slowly.
The default percentage of the scan dedicated to
processing communications requests is set to
10%. This setting was chosen to provide a
4
reasonable compromise for processing the
compilation and status operations while
minimizing the impact to your control process.
You can adjust this value by 5% increments up to
a maximum of 50%. To set the scan cycle
time-slice for background communications:
1. Select the View > Component >
System Block menu command and click
on the Background Time tab.
2. Edit the properties for the communications
background time and click OK.
3. Download the modified system block to the
S7-200.
The S7-200 Allows You to Set the States of Digital Outputs for Stop Mode
The output table of the S7-200 allows you to determine whether to set the state of the digital output points
to known values upon a transition to the STOP mode, or to leave the outputs in the state they were in
before the transition to the STOP mode. The output table is part of the system block that is downloaded
and stored in the S7-200 and applies only to the digital outputs.
1. Select the View > Component >
System Block menu command and click
on the Output Table tab.
2. To freeze the outputs in their last state,
select the Freeze Outputs check box.
3. To copy the table values to the outputs,
enter the output table values by clicking the
checkbox for each output bit you want to
set to On (1) after a run-to-stop transition.
(The default values of the table are all
zeroes.)
4. Click OK to save your selections.
5. Download the modified system block to the
S7-200.
40
Figure 4-21 Communications Background Time
Figure 4-22 Configuring the Output Table
1.
2.
1.
2.
3.