Hans:
The idea is to use a FLASH part with ISP (In System Programmability) requires a simple adapter from your PC comm port or parallel port.

Its time for you to look more specifically at moving up to the modern implementation for large programs.

Look at the P89C664 part from Philips. If your board had a standard type PLCC packaged processor, you should be able to drop this part into the same socket and immediately have 64K of FLASH. I believe that the ISP programming adapter is something that is documented and easy to build yourself if you wish. The supporting programming software is free and available for download off web sites.

My conclusion is that it would be silly to get into programming old style EPROMS, EEPROMS, or even 28Fxxx type external FLASH chips. All you have to do is read a couple of processor data sheets, scan through the Philips web site and search this forum for part numbers like P89C662, P89C664, or P89C66x. Make that investment and you will, I assure you, wonder why you ever though the external program memory was a good idea.

If you want to move way up to high tech look at the Cygnal parts. Along with the advantages mentioned above you also get hardware debug support on every chip. You can say good bye to the "burn and learn" program debug scheme, or debugging with crappy monitors, or debug using expensive in-circuit-emulators. And with a Cygnal part with the elegant way their IDE and FLASH support works coupled with the hardware debug support works, you will never use a simulator again!!

Michael Karas