TMR0 stops working

[shahidali55]

Decoupling capacitors don't seem to help . . .
Using the 16F628A with MCLR disabled while programming solves the problem (for now)...

[Archangel]

Hi shahidali55,
If your display is large and has long wires , it may well be acting as an antenna, try decoupling caps on each output line going to it, as well as any inputs, also try hooking all ground connections to a single ground connection, as ground loops often cause electronic circuits to oscillate, That is what they used to do in high end audio gear.
HTH
JS

[shahidali55]

Hello Joe,
My display is large and there are a lot of long wires running around and there are 2 ground loops.
How should i add decoupling capacitors to the output and input pins ?

I have attached a few photos of the complete clock and PCB side. . .
(They may take a while to download)

[Archangel]

Hi shahidali55,
On the perfboard I would probably run a buss wire lengthwise under the pic and from each pin I would add .o1uf or even .001 uf capacitors to the buss wire which is hooked up to ground, I think you are getting RF into the chip from the outputs, RF is funny, it sort of crawls on the outside of conductors and does funny things. AS for things like cellphone chargers emitting RF I guess it depends upon which country's emission standards they meet or fail to meet. You might try using 2 bypass caps, 1 from each leg of the Mains power to ground right at the outlet. Ferrite beads are useful to trap RFI on wires on the circuit board. Be sure they are made for that high of a voltage,otherwise they pop like firecrackers Some links on RFI:

http://www.edn.com/archives/1995/010595/01df1.htm
http://www.eham.net/articles/12139

[shahidali55]

16F628A has been running stable for 10 days now.(Tried doing all sorts of things to make it reset, but its immunity is really good).
So i guess the only solution is to stick with the 16F628A . . .

[shahidali55]

My problem is still very much alive.
I had turned off the clock for over a month.
Now the clock "locks up" within 48 hours.
It has locked up twice at 7 hours , 14 minutes (7:14).
The mux routine works fine but the ISR just stops updating timing registers.
(The varibles that handle this are bres_hi ,bres_mid ,bres_lo.)
(uC is 16F628A and TMR0 used ot keep time)

[Darrel Taylor]

I'm still thinking it's related to voltage.

The device is being powered by 3.6V
But the 16F84A is only specified to work down to 4.5V

In post #3 you said the datasheet specifies 2.0V
But that's only for the 16LF84A

Edit: Doh! You're using the 628 now. Nevermind.
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