11 Mar
2015
11 Mar
'15
6:59 p.m.
On 03/11/2015 12:45 PM, Rick Bensene wrote:
OK, while we're on the topic of core memory sense
circuitry, in some of
the old calculators that I've come across (a good example being the
Casio AL-1000 -- http://oldcalculatormuseum.com/al1kck10l.html) ) there
are transformers (pulse transformers) in the core memory sense
circuitry. What purpose would these serve, and why are they used in
some core memory applications, and not in others? In the case of the
AL-1000, similar transformers are used in the X-Y drivers as well.
I think most core memories that use the 3-wire scheme use
transformers to
couple the sense amps. The older, 4-wire scheme used
separate wires for the
inhibit wire and the sense wire. When merging those (which
allowed smaller
cores, thus faster cycle time) you had a bunch of driver
transistors attached to
the sense/inhibit winding, which may have unbalanced the
line, affecting the
balance of the sense amp. Well, I think that is somewhat
close to the
reason for them.
Jon