Special Message #3: Reset Dl20; Special Message #4: Test Battery; Special Message #5: Print He Stack - Allen-Bradley A-B QUALITY DL20 Series User Manual

Special Message #3: Reset DL20

Special message #3 has the same effect as cycling power. This is useful if
you want to run the powerup self test. This is sometimes useful for systems
that have a system test function. If you send the DL20 special message #3
when the test button is pressed, the display will go through its self tests.
Triggering special message #3:
terminates the display of any message running
clears message and data queues
causes the autorun message to be displayed
Special message #3 exactly mimics the conditions that occur when the power
is removed and then restored.

Special Message #4: Test Battery

Special message #4 tests the battery. When special message #4 is triggered,
the battery is tested and a message is shown, either BATTERY OK or
BATTERY LOW. Although the battery is normally checked on powerup,
some applications are running continually. Special message #4 provides a
way for your programmable controller to periodically test the battery. If the
relay flags battery special function is selected, then the relay is energized
each time special message #4 is triggered and the batteries are low.

Special Message #5: Print HE Stack

Special message #5 prints the contents of the Historical Event (HE) Stack,
with the most recently stacked messages printed first. Messages are not
removed from the stack as they are printed. Messages are printed until the
entire stack is printed, or until stack printing is halted by triggering special
message #6.
While the HE Stack is being printed, any message triggers or variable data
that are received are stored in the queue. If a message trigger is received
while printing the HE Stack, it is displayed when you terminate printing or
when the entire HE Stack is printed.
Chapter 5
Run Mode
5–7