Low power aplication on 12F629

[cncmachineguy]

but still for timing applications you need an external Xtal, INTRC its not enough after some days running

Sounds like a test is in order. Are you saying that after a few days the clock is no longer at said speed? by how much? I can see a test such as this:

main:
 toggle port pin
 goto main

this will give some freq out. so if we let it run a few days, we can see the new freq out.

[El_AMPo]

Sounds like a test is in order. Are you saying that after a few days the clock is no longer at said speed? by how much? I can see a test such as this:

main:
 toggle port pin
 goto main

this will give some freq out. so if we let it run a few days, we can see the new freq out.

It's a clock keeping code so you work "accumulating cycles", if you use an RC source, even if you calibrate it to a perfect frequency within a few days you will have noticeable drift because of temperature changes during the day and voltage drop from the battery. Crystals also suffer from drift but much less noticeable, and if you want better than that you will need temperature compensated RTCs or OCXO (oven controled crystal oscillators) both an overkill for my clock.

Talking about INTRC 4mhz clock... anyone was able to calibrate the value at 5 volts via oscal value?.
The factory default is calibrated at 4mhz 1% BUT at 3.5V 20ºC if I remember well. So at 5V it's like 1.1Mhz per instruction actually (measured), that means goodbye serial comms and reasonable good timing.

[cncmachineguy]

1.1Mhz per instruction actually (measured)

WOW, thats 10%!!!!