[Tech] 27C2001 / 4001 compatibility...

[guddler]

[ukvac] [Tech] 27C2001 / 4001 compatibility...
I briefly touched on this on irc last night, but...

Someone wants me to burn a rom onto a 27C2001 for them. No problem. I only have
one or two of these left. Again, no real problem as i know several people can
supply them, including RS, but to save pratting about with getting the guy to
send me money, i looked at the data sheets.

It would appear that the only difference between the 27C2001 and the 27C4001 is
that on the larger IC pin 31 is A18, whereas on the smaller one it is "not P"
(program inhibit?).

As i have a lot more 4001s than 2001s, would i be right in saying that i could
just double up the 2mbit image onto the 4mbit IC and tell the guy to leave pin
31 sticking up in the air before installing it? Preferably i would break this
pin off before posting it to him. Or would i nead to bend it up in the air and
stick a patch wire to the ground pin?

If neither of those are the case, it's not a biggy, but it would make my life
easier and cheaper if i can do this...

Cheers,
Guddler.

 

[andrewhannay]

RE: [ukvac] [Tech] 27C2001 / 4001 compatibility...
If you are doubling up the image anyway then you don't need to do anything
with the pin.
The PCB will have this pin hard wired to 5v or 0v anyway. If it's wired to
0v then the lower half of the ROM will be used and if it's wired to 5v the
upper part will be used. As you have programmed both parts the same code
then it makes no difference.

Andrew

 

[guddler]

RE: [ukvac] [Tech] 27C2001 / 4001 compatibility...
Doh! So easy really!

So, I'll just double check the pinouts on those datasheets and away we go...

Ta.

> If you are doubling up the image anyway then you don't need
> to do anything with the pin. The PCB will have this pin hard
> wired to 5v or 0v anyway. If it's wired to 0v then the lower
> half of the ROM will be used and if it's wired to 5v the
> upper part will be used. As you have programmed both parts
> the same code then it makes no difference.
>
> Andrew
>
>

 

[Macro]

Re: RE: [ukvac] [Tech] 27C2001 / 4001 compatibility...
it *may* cause problems if it's floating, as the address may not be
stable which affects the response time. So definately don't cut it off!

If you really want to be sure, bend it up and across pin 32 and solder
it to that.

Martin White <martin@guddler.com> wrote on 13.08.2003, 13:28:57:
> Doh! So easy really!
>
> So, I'll just double check the pinouts on those datasheets and away we go...
>
> Ta.
>
> > If you are doubling up the image anyway then you don't need
> > to do anything with the pin. The PCB will have this pin hard
> > wired to 5v or 0v anyway. If it's wired to 0v then the lower
> > half of the ROM will be used and if it's wired to 5v the
> > upper part will be used. As you have programmed both parts
> > the same code then it makes no difference.
> >
> > Andrew
> >
> >