Memory Tests; Figure 8 Led Indicators On The Pwc22 Board - Vaisala PWD22 User Manual

Chapter 3________________________________________________________ Functional Description
VAISALA ________________________________________________________________________ 33
The software generates alarms, if visibility is less than a given limit.
PWD22 generates warnings of suspected faulty hardware. If a fatal
hardware failure is detected, visibility data is not generated; it is
substituted with slashes (/////). A status message displays the cause of
the error in status bits.
Built-in tests include memory test, analog monitoring, and signal
measurement monitoring. Results of the monitoring measurements are
displayed in volts or hertz depending on their origin.
Program operation is monitored by the watchdog circuitry. If the
circuit is not triggered in about two seconds, it will perform a
hardware reset.
Figure 8 LED Indicators on the PWC22 Board
Normal operation is indicated by the Run LED blinking once every
second. The Signal/Offset LED is on, when PWD22 measures the
visibility signal.
The RxD and TxD LEDs are directly controlled by the serial line
hardware indicating all action in the serial line.

Memory Tests

After resetting, PWD22 tests and clears its SRAM data memory. It
indicates an error by the Signal/Offset LED blinking. After 50 blinks
PWD22 tries to start the program anyway. Usually this causes a
watchdog reset, if the SRAM is really faulty.
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