15 Apr
2006
15 Apr
'06
3:58 p.m.
I was somewhat shocked to find out that my TopMax
EPROM programmer doesn't handle the vintage 2708
1k x 8 EPROM. A very interesting little EPROM
the 2708. It requires +5, -5, and 12v.
From what I remember, the 2708 is 'fun' to
program for suitable values of
fun. IIRC, some of the pins (and not just a steady
Vpp pin) have to be
raised to voltage abobe TTL during programming (I can't remember if you
have to over-voltage the data lines, or if that's just for the 1702).
And officially you can't program odd locations. You're supposed to go
through the whole 1024 locations giving each one a short programming
pulse, and repeat that <n> times. You're not supposed to supply <n>
pulses to one location and then go on to the next. Last time I mentioned
this (and it is in the data sheets), people here told me you could get
away with progrramming individual locations, though.
Anyway, any advice out there for working with
these old little beasties? I'd like to first
read one, but eventually program them. Or
Reading is not too hard. OK, you have to provide +12V and -5V supplies,
but apart from that it reads like any other EPROM.
maybe I should program the 2716 and substitute
them (with appropriate bent-up pins)? Maybe,
too, I could read them after telling my TopMax
it is a 2716 and (again) bending up a few pins,
or maybe using a pulled-pin socket.
That depends on how 'clever' your programmer is. If it does checks like
making sure the supply current is reasonable, it may well fail.
As regards programming them, there were many projects for 2708
programmers in the magazines almost 30 years ago. I'd read a few, and
then decidn to kludge in 2716s or something :-)
-tony