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Ok FWIW...WD timer info:
WD = Watch Dog, in general is a mechanism for monitoring the CPU state, both for lock ups or a program is getting lost, ....not clearing the watchdog timer. Watchdog timers are used to bring microprocessors out of an endless loop. It resets the microprocessor if the timer is not reset. A normal running program will keep the watchdog timer cleared. If it is not cleared, it will time out, give an error message and reset the processor to a known starting position.
Some causes:
U3, MCP-450. In Gemini I know it monitors the voltage of the power supply +5V to the CPU - if it goes too low it resets the processor. You can remove this U3 for testing.
One cause can be the F2 resettable fuse dropping too much voltage (usually when a peripheral is plugged into the serial port), but this depends on which version PCB. The older versions had no F2 so D10 could be suspect.
If you have an older unit then this fuse F2 (re-settable polyfuse) probably needs replacing.
Check and make sure that your battery is fresh. Make sure that the EPROM is firmly seated into it's socket. Also make sure your power supply is supplying at least 12V.
You could have a bad battery, or maybe a EPROM going bad.
I have sen one fixed with a new programmed EPROM.
Also the RTC and SRAM both share the same data bus and both can spoil the other's operation and cause a WD reset if faulty.
Thus if you see it once...ok ....but if its happens all the time...clear SRAM data and re-enter data to clear the WD reset on power up.
regards
Brendan
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