config word question

[vortech1]

sir nigel,

i've observed in your tutorial for the pic16f628 that in your config line you placed
__CONFIG 0x3D18

meaning PWRTEN is disabled why is this?

when i'm programming pic16f84 i always do _PWRTE_ON

what really does pwrte do?

based on some web site and from what i know it is used so that the pic is in reset until vdd reaches the voltage needed for proper operation. by disabling it what does it do then?

 

[Exo]

yes, it's a timer that keeps the pic in reset for a short while on power up so everything can settle down before the program starts running...

By disabling it the pic starts running directly, If the pic has a clean power supply and no devices are on the same power line that may need a high startup current then it will probabely be ok without the timer

 

[Nigel Goodwin]

sir nigel,

i've observed in your tutorial for the pic16f628 that in your config line you placed
__CONFIG 0x3D18

meaning PWRTEN is disabled why is this?

when i'm programming pic16f84 i always do _PWRTE_ON

what really does pwrte do?

based on some web site and from what i know it is used so that the pic is in reset until vdd reaches the voltage needed for proper operation. by disabling it what does it do then?

As you say, the 'Power Up Timer' delays the reset, giving the power rail more time to settle down - but this is very rarely needed. Feel free to turn it on if you want, but I've never found any need to.

If the power rail takes a fairly long time to come up, it could be useful, but generally a power rail comes up plenty fast enough - particularly when fed from a 7805 as in the tutorials.

In your existing 16F84 projects, try turning it off and see if it makes any difference?.