Siemens SIMATIC S7-200 System Manual page 58

S7-200 Programmable Controller System Manual
Tip
Changing the range MB0 to MB13 to be retentive enables a special feature that automatically
saves these locations to the permanent memory on power down.
To define the retentive memory:
1. Select the View > Component >
System Block menu command
and select Retentive Ranges.
2. Select the ranges of memory to be
retained following loss of power
and click OK.
3. Download the modified system
block to the S7-200.
The S7-200 Allows You to Filter the Digital Inputs
The S7-200 allows you to select an input filter that defines a delay time (selectable from 0.2 ms to
12.8 ms) for some or all of the local digital input points. This delay helps to filter noise on the input
wiring that could cause inadvertent changes to the states of the inputs.
The input filter is part of the system block
that is downloaded and stored in the
S7-200. The default filter time is 6.4 ms.
As shown in Figure 4-23, each delay
specification applies to groups of input
points.
To configure the delay times for the input
filter:
1. Select the View > Component >
System Block menu command
and select Input Filters. Click on
the Digital tab.
2. Enter the amount of delay for each
group of inputs and click OK.
3 3. Download the modified system Download the modified system
block to the S7-200.
Tip
The digital input filter affects the input value as seen by instruction reads, input interrupts, and
pulse catches. Depending on your filter selection, your program could miss an interrupt event or
pulse catch. The high speed counters count the events on the unfiltered inputs.
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Figure 4-22 Retentive Memory
Figure 4-23 Digital Input Filter