[sdiy] 8031's & serial EEPROM's? for MIDI...

[Ingo Debus]

Am 03.11.2006 um 17:02 schrieb anthony:

> When your electronics budget per month is $0.0 and your monthly  
> parts expenditure ends up being ~$40.00 you have to think of  
> creative solutions for things or... wait. It's part of my personal  
> philosophy to use what I have first. And I have TONS of parts - I  
> just have to think of creative ways to use them. If I can't come up  
> with a clever or elegant use for them, then I move on.
>
> I have tons and tons of shift registers and shift register latches,  
> both CMOS and TTL, 74194's, 4094's.
>
> But I looked on eBay a little bit ago and it would probably be most  
> cost effective for me to get a UV lamp for erasing EPROMs as I have  
> scores of 27XXX EPROMs with things on them. And burners look pretty  
> cost effective too... I love eBay.

Can't EPROMs be erased by being exposed to the open sun for long  
enough? No idea if that would work, perhaps the UV wavelength isn't  
right.

For interfacing a 27xxx EPROM to a 8031 you still need one other  
component: a 74x373 or 74x573 latch.

However, with only an EPROM as program memory, software development  
by burn-and-learn gets very tedious. You're much better off with  
additional RAM as program memory (on the 8031 program and data memory  
are not the same by default, but you can use one RAM chip for both).  
Have some bootloader in EEPROM to get your code into RAM to test it.  
Once your program works (and doesn't need to much data RAM) you can  
remove the RAM or re-build the thing without RAM. The 8031 has a tiny  
on-chip data RAM.

With Flash on-chip program memory all those issues are non existent.

Ingo