Programming 2708's

[Tony Duell]

> Intel changed the specifications of the 2708 a couple of times, later docs 
> state it does not require programming from address 0.

But did they also change the design of the chip, I wonder. Later 2708s 
may be more forgiving as to the programming algorithm they'll accept.

Since Intel were so definite about having to go through all locations in 
order n times in the data sheet I have, I would certainly want to do it 
that way. Other methods might well damage the chip or lead to poor data 
retention.

> 
> I have changed individual bits (only from a high to low, to go from low to 
> high the entire chip must be erased).

You can change individual bits, sure. The data sheet tells you how to do 
that.

You have to go through _all_ the locations. If a locations is to be 
unchanged, you program it again with its current contents (a special case 
of this is that if you want to leave a location totally unprogrammed 
after erasing the chip, you re-write it with 0xFF).


> 
> The later docs still state sequential writing but no longer require starting 
> at 0 but I have written non sequentially and can swear by that.  I wrote a 
> program that verified before writing to speed up programming, this skipped 

Oh, it probably worked. But I wouldn't recomend doing it. 2708s are 
getting harder to find, so I'd not want to risk damaging one. And I 
certainly don't want to have to trace a fault caused by an unreliable bit 
in an EPROM. I would follow the manfacturer's instructions...

It reminds me af a friend who programmed 27128s with a single 1ms pulse 
per location. It seemed to work. They verified OK. And then a bit later 
on he got data-rot....

-tony