Siemens simatic hmi op27 Equipment Manual page 204

Internal functional
units
OP27, OP37 Equipment Manual
Release 05/99
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Display Test Initiated by Key
DISPLAY
K7
Functional Initiated by Key
Unit Test
WATCH-
K8
DOG
RTC/
K9
BATTERY
TEST
K10
ENTRIES
T est Functions
Result
The display test consists of the following
four individual tests, each of which can be
performed on its own:
White
Pixel test of the screen surface,
the entire display goes white.
Black
Pixel test of the screen surface,
the entire display is blanked.
Grid
The grid lines are displayed.
Characters
The character set is displayed.
Result
This test verifies whether the watchdog,
once triggered, initiates a restart when the
trigger stops.
The battery connection and hardware
clock are tested (floating bit test).
This function is reserved and must not be
selected.
C-5