TMR0 stops working

[shahidali55]

Hello Darrel,
As you suggested in post 2, the battery now charges from output from the 5v regulator (through a diode and a 2.2k resistor). The voltage at the PIC never rises above 4.6v. I tested this system with a 20v DC supply and the voltage at the pic pins is still at 4.63 volts (after 48 hours of running).

I have attached a copy of the file with the required include (Instant interrupts) as a zip archive.
The pushbuttons are not a concern now since the primary function of the device itself
(i.e. keeping time) is not met.

Is ASM opcodes in column 1 bad ?

[Darrel Taylor]

I have attached a copy of the file with the required include (Instant interrupts) as a zip archive.

I don't understand why you've modified DT_INTS-14 like that. There's no need.
I also don't like modified versions being posted on the Internet. Somebody will download it, it won't work, and then they'll blame me.

Is ASM opcodes in column 1 bad ?

Yes! Very BAD!
ONLY Labels can go in the first column of ASM code.
This applies to lines using the @ sign too. There must be a space after the @. (unless it's a label)

With opcodes in column 1, the program won't compile. So that can't be the program you are currently running in the chip.

DT

[shahidali55]

Strange . . .
Compiles fine for me.
I have corrected the OPCODE in column 1 errors and attached another copy of the file.
Sorry for modifying DT_INTS-14 , it it your work and i respect that. I modified it in my frustating attempts to correct the resetting and locking up of the chip.
(still getting 3 warnings though)

[Darrel Taylor]

That is Strange! Wouldn't compile here the way it was before.

I can't see anything in the program that would cause it to lock up.
So I put together a breadboard to see what I could see.

click image for larger version

It's running on a 16F88 right now. Couldn't find my 628A.

I'll see if it makes it past 7:14 first.
Then set the time, and let it run.
Hopefully I can find that 628A by then.

I'll let you know if it locks up.

DT

[shahidali55]

Thanks DT.
That is one really neat breadboard.
Did you notice the hourly on screen animation?


Just after the two LOOKUP statements there is a tricky piece of code that used to blink the colon:-
;if bres_hi<8 then
; Segments.7=0
;else
;Segments.7=1
;endif
It is there in the code posted in #1.
The code in post #18 has this part commented. Hence no blinking colon.
But after 4 days of testing with this code (#18) everything seems to be fine.
Could the blinking colon code have caused the problem?
To blink the colon, i used to check a critical time keeping variable (bres_hi) of the 24 bit counter. I think if bres_hi was being read when an interrupt occured and the ISR tried to update the register, it got corrupted. Can this happen?

[Darrel Taylor]

It is pretty neat isn't it? I'm actually thinking about hanging it on the wall just like it is.

It's still happily keeping time. No glitches so far.
I can't image that the blinking colon would have made any difference, but I'll uncomment it just for diligence sake.

Yup, I saw the animation. That's cute. Also saw the upside down digits that I can see in your previous pictures, were mounted that way. Accidental??
I commented out the extra Lookup and IF statement.

Still haven't found the 628A, but I don't think there's enough difference to matter.
I suppose I should put a battery in there and run it at lower voltages too.
<br>

[shahidali55]

I'm actually thinking about hanging it on the wall just like it is.
<br>

Not a bad idea. A clock does always comes in handy.
The last 2 digits were put upside down so as to get a colon from combining the two dot points on the oppositely placed standard 7-segment displays. An extra lookup table was the overhead.
If the clock is loosing or gaining time, you can adjust bres_lo reload value in the ISR.
(+.25 sec/day = bres_lo - 8 , -.25sec/day = bres_lo + 8).

Running it on a battery down to 2.1v will be the ultimate test.
My chip seems to have no problem till 2.1v. Below that the oscillator stalls and below 0.9v the ram gets corrupted.