8080 Assembler-Text Editor (ATE)

Don Y dgy at DakotaCom.Net
Wed Apr 19 20:59:34 CDT 2006

Tony Duell wrote:
>> What was more amusing was two different versions -- "with tails" and
>> without!  :>
> There's also the 'hooked 7' (segments a,b,c,f using the conventional 
> names), used by some Japanese manufacturers. AFAIK no TTL decoder ever 
> generated that one. 
> In the mid 70's there were several circuits in the UK magazines to turn 7 
> segment code back into BCD, so you could use clock/calculator/DVM chips 
> with built-in display drivers in other logic circuits. Most of those 
> encoder circuits, of course, made liveral use of the 'don't care states'. 
> Some of said circuits would handle both tailed and tail-less 6's and 9's, 
> but IIRC most of them failed on hooked 7's.
>>> That said, I think it is a pity there wasn't a later TTL 7 segment 
>>> decoder chip (say a 74LS547 or something) that did display 0-F as you 
>>> might expect. 
>> *Something* does this -- though I may have been driving LCD's
> There was a Fairchild one, I forget the number.
>> at the time (thus CMOS parts).  But, I remember a 7441 (though
>> what I used it for I am unsure... :< )
> 1-of-10 decoder, commonly used to drive nixie tubes.

I used a 7447 to replace the front panel on a Nova 2 (3?).
The OC outputs fit the Nova's bus nicely.  And, by a bizarre
twist of coincidence, some of the digit encodings would
perfectly match the data intended to be seen on the bus
when a certain (reduced!) set of front panel switches
were keyed.  So, we could boot, step, etc. a preloaded
core image without having all of that hardware dangling
off the front of the machine.

More information about the cctech mailing list