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what is a MM5422N ?

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retiredfeline:
It's really a simple duplexing scheme. Half the segments have a common anode connection and the other half the other common anode connection. So from 12 pins you can get 24 independent segments. 3 digits for M, 10M and H = 21 segments, segment B and C for 10H = 2 segments, and last segment is for PM indicator. Each output pin is labelled with 2 abbreviations. For example: HUB = hour units segment B, MTC = minute tens segment C. You could connect up 24 LEDs and figure out which side of the centre-tap winding will activate which half.

The scheme is slightly modified for 24 hour display. In that case there are "segments" HTB, HTC, and HTADEG, so that it can display nothing, a 1 (B+C), or a 2 (B+ADEG). The PM "segment" is then not needed. Clever.

Your biggest problem will be getting a suitable display. You could make segments with chained LEDs but that's a lot of soldering.

tooki:

--- Quote from: amyk on December 22, 2020, 12:01:39 am ---
--- Quote from: tooki on December 21, 2020, 11:00:30 am ---Could they be the ones mentioned in this PDF? https://media.searchelec.com//specshee/NATIONAL/NationalSemiconductorOptoelectronicsHandbook1979_text.pdf

(too big to attach)

--- End quote ---
That's not a "databook", it's a "handbook" with only brief descriptions of the parts.

--- End quote ---
Why the attitude?!?  :-//

I described the PDF as "this PDF", without making any claims as to what kind of document it is. The file name clearly says "handbook". And given that it's literally the only document on Google with any information whatsoever about this part, it's better than nothing…


--- Quote from: amyk on December 22, 2020, 12:01:39 am ---Looking in the 1977 MOS LSI databook which has a bunch of clock ICs, there's MM5402 and MM5405, but not 5422, so it was introduced probably '78 or '79.

--- End quote ---
If it's not in the '77, then it's not "probably" introduced in '78 or '79, but necessarily, given its presence in the '79 book.

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