dual 7-segment countdown timer code

[precision]

i've said that hundreds of time on many forums... they're good for lazy prototyping and/or in a well shielded enclosure. In harsh environment, they could (and sure they will) be a real pain in the... but on the flip side, it may work good... and maybe long enough to cover the warranty time

i NEVER use pull-up, never use the 'Set your pin as output and let'em floating in the air' The theory is hum hum good, but... will your design will always be powered? What happen with those pull-up when you remove the power... they're software enable after all!

Please explain what is the problem in pullup, if chip have pullup feature ?
i ever useing OUTPUT PORTB.0 , is this wrong way ? Please tell what we must...


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[mister_e]

it can be useful in few situation : tight space, mass production with tight budget, Push-button handling, prototyping, etc etc. They're weak, and may cause some problem (noise, ESD, strange behaviour, etc etc) one day or another. I got few ESD and erratic problems in the past with that in noisy environment, since i add external one, no more problem!

It's a long debate, some never ever had problem with... too bad i no longer take the risk.

[precision]

Thanks, one more Q. please
what should we use instead of output pin / input pin. I mean tbe best way to make input output pin ?

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[BobK]

Hi Precision,

I think what Mister E is saying is always use an external resistor either in a pull up or pull down situation. Don't make an unused pin an output and just leave it floating. Look at the data sheet for the particular PIC you are using and search for the state of the pins ON RESET. If you are leaving a number of pins unused and they start as inputs on powerup or on reset then you need to make sure they are properly terminated with a pullup or pulldown resistor.

HTH,

BobK