Thanks for your reply, However, my 16c84 IC's can be programmed and erased many times so I presume you are meaning the 12cxxx range of IC's which are 'one timers'.

I do have a jewel windowed 12c509 so I am able to re-programme it but, admittedly, after it has been under the sun lamp.

So, can I presume you suggest developing the software on a EE flash type pic then once I am happy with it look at putting on to a 12cxxx pic?

If so, then can you help with the first few lines of the code which are concerned with setting up the 12cxxx range of IC's, ie setting up the ports.

Thanks again