Iomec disc drive ?

From: Brent Hilpert <hilpert_at_cs.ubc.ca>
Date: Fri Jan 2 04:55:40 2004

Bob Shannon wrote:
>
> Those are NOT DTL chips!
>
> Your looking at CTL logic, which uses a circuit similar to an uncommited
> emitter output rather than the
> conventional totem-ploe output stage.
>
> There are no drop-in replacements, and you cannot use DTL or TTL parts.
>
> Jay Jaeger wrote:
> >
> > The logic in my IOMEC 1802 controller that is unhappy has Fairchild
> > chips -- not standard 74xx fare. It may well be that they are DTL
> > (sample markings on one are DT uL909759 7020), which I am currently
> > guessing is a 9097 chip.
> >
> > Jay Jaeger
> >

I don't have a reference for exactly "DT uL909759", but based on my (albeit limited) experience with an HP 2116C that recently came into my possession(*), I think the situation may be a little more complex/subtle.

(*: a real blinkenlights machine, forget LEDs: over 80 incandescent bulbs :) (the downside being the bulbs are difficult to get).)

The majority of the innards (CPU/memory) of the 2116 is based on Fairchild CTuL: Complementary Transistor MicroLogic. This is a form of emitter-coupled, non-saturating, current-mode logic. It might be described as an early ECL family, or a precursor to the more standard/common ECL families. Supply voltages are +4.5V and -2V. However, some of the I/O controllers for my machine uses both CTuL *and* standard TTL, with the TTL running (borderline) off the 4.5V supply.

A Fairchild booklet (Fairchild Semiconductor Integrated Circuits) from 1966 which covers Fairchild's product line, from RTL/DTL/TTL,CTL/linear,early MOS,etc. (a great 'period' snapshot of early IC technology, complete with discussion of logic families, IC pinouts and full page colour photos of IC internals in lovely 60's colours), presents the following part numbers:

    under DTuL, Low Power: (Diode-Transistor Logic)
       9040, 9041, 9042

    under DTuL: (Diode-Transistor Logic)
       ..., 9951, ..., 9961, ...

    under CTuL: (Complementary-Transistor Logic)
       9952, 9953, 9954, 9955, 9956, 9957, 9964, 9965, 9966, 9967, 9968, 9971

    under CuL: (yet another logic family: Counter MicroLogic, not to be confused with CTuL)
       9958, ..., 9960, ...

    under TTuL: (TTL of course)
       9000 ... 9009

(Note: the u in these logic family names is actually greek 'mu'/micro)

While individual 4-digit part numbers are exclusive to a particular device (i.e. 9958 does not show up in two logic families (although I can't answer for what happened after 1966)), there is little to be said for grouping of logic-family <--> number-sequence.

...back to "DT uL909759 7020", the 7020 is presumably the date code; what the "59" digits are doing there I too would like to know (I have run across other HP equipment with, for example, a Fairchild IC "CuL 996079", whose functionality matches that of the CuL 9960 listed in the above booklet). My guess, as you (Jay) guessed, is that your chip is a Diode-Transistor-Logic 9097 (dual M/S J/K FF), but as Bob indicates, you may be dealing with CTuL in the rest of the machine or even on the same board.
(Actually, I would be curious to know whether the 2114 used CTuL, like the 2116, or whether HP did two versions of the CPU logic and used slower, less-power-hungry DTL in the 2114.)

Another possible way to distinguish ICs of the two families: the booklet shows all the DTuL ICs with standard Vcc=pin 14 and GND=pin 7. On the CTuL family, supplies are Vcc=pin 12, GND=pin 5, Vee=pin 11.
Received on Fri Jan 02 2004 - 04:55:40 GMT