Hi Dave,
A couple of small things noticed:
1) You can read the value direct into X instead of first reading it to Z and then copying it to X. Nothing wrong with what you're doing it'll just save some program space and time.
2) The line GOSUB RAN: looks strange. First, there shouldn't be any colon after the label in the jump statement, only where you declare the actual label. Second, you don't want to GOSUB a routine from which you don't RETURN. In this case it may work but it's generally a bad idea.
3) Speaking of GOSUB and GOTO, you are making a couple of unneccessary jumps. At the beginning you say GOTO Power_Up even though the next line in the program is the beginning of the Power_Up routine. Same thing when Power_Up is done, then you jump to RAN which already is the next line so it will get there without needing to jump to it.
Now, if you have some other code "in between" then it makes sense, and as you've found it, it works the way you have it but it's not needed.
4) The EEPROM has a limited number of write-cycles. We're talking tens or even hundreds of thousands of cycles but if you write to it on average ever 1500ms, 100.000 writes are less than 42 hours.
There are ways to get around that but it requires a little hardware and the use of interrupts. Basically you have a capacitor that allows the PIC to stay powered long enough to make the EEPROM writes. The capacitor is charged from your powersupply thru a diode. Then you have a "direct" wire going to an input on the PIC which fires an interrupt when the powersupply goes down (the cap is keeping the PIC alive).
Again, just a couple of small things to consider. Good job!
/Henrik.
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