If a port pin is unused, it may be left unconnected but configured as an output pin driving to either state (high or low), or it may be configured as an input with an external resistor (about 10 kΩ) pulling it to Vdd or Vss. If configured as an input, only the pin input leakage current will be drawn through the pin (the same current would flow if the pin was connected directly to Vdd or Vss). Both options allow the pin to be used later for either input or output without significant hardware modifications.

 

I am not getting any pic 12F629 chip here....please provide other alternatives ....

 

There are other PICAXE chips, with much more I/O and much more memory. You might be able to run your current programs with just minor modification. If you use a different chip, you will have to use a different circuit. However, chips like the PICAXE 14 series and 20 series share a very similar physical configuration to the 08. And both re far more powerful than the 08. Look at their current documentation to see what I mean.

Also, like I said before, the PICAXE 08M is currently available, has the same pin-out as the 08, has more capability and twice the memory. 99% of programs that run on the 08 will run just fine on the 08M. And no circuit modification will be required.

Furthermore, PICAXE make chips with 8, 14, 18, 20, 28 and 40 pins. They all use the same language (with some specific commands that might be different) and offer huge capability. So you can expand to whatever extent you want without having to learn a new language or development environment.

If there is no one in your area selling PICAXE, you can order them directly from the manufacturer.

Forgive me, but it seems to me you are making this more complicated than it is. Just go to http://www.rev-ed.co.uk/picaxe/, look at what they have and order what you need.

 

@billo,i have just 3 days time and i dont think it can shipped so quickly and circuit can be designed .....

sorry if was rude...

 

No saying you were rude Jose, just trying to make a point. I do not think there is another solution to be had in 3 days. Maybe they can over-night one to you by courier. There would not need to be any re-design using the 08M if the design worked with the 08.

What part of the world do you live in?

 

asia

and i would be happy to work with any 8051 based alternative..but experienced guys like you need to help me with that......i want to work with 8 pin muc only

 

Is this school work. Because maby your teacher can get you a new chip. killing chips is a part of the development game

 

Getting the 8051, a programmer, a compiler and possibly an IDE, learning all that, and leaning the curve to design with a new chip is not something that, I think, can be accomplished in 3 days.

The manufacturer is in England, maybe they can get you one in a couple of days. Call them. It's all I can think of right now.

 

Check ebay and online electronics shops in your area. A lot of places carry them.