Programming 2708's

[Tony Duell]

> 
> > the Intel data book makes it very clear you do have to program
> > all locations.
> 
> > The unchanged ones have to be reprogrammed with their existing
> > contents, you can't skip over them. 
> 
> Not true on both counts, you only need to go through the program
> cycle for bytes that need to be programmed and if you want to leave
> a byte unchanged but still go through the program cycle then you
> set the data to $FF as bits can't be programmed high.

The Intel data sheet disagrees with you.... 

> 
> What the data sheets say often did differ from the practice, even
> on official programmers.

Maybe so. It probably works fine. But I will not deliberately go against 
the manufacturer's specifications. It may save a couple of minutes now, 
but it may also waste a few hours later tracking down an obscure bug....

> 
> I used to use 2708s in CB to 11m conversions and got away without
> the -5v supply by using a lamp to illuminate the chip and generate
> the -ve bias photoelectrically, this only worked with one brand of
> EPROM though.

I'd much rather use a charge pump circuit and do it right. 

-tony