31 Oct
2011
31 Oct
'11
11:59 p.m.
On 2011 Oct 31, at 3:17 PM, Tony Duell wrote:
I'd say multiplexing generally was initially done to save on logic
and hardware. One 1-of-10 decoder instead of 12 or 16 of them, and 10
+12 drivers instead of 120, for example.
There were a few early calculators that did static registers with per-
digit decoders and drivers, but they quickly went to multiplexing, in
the days of discrete and SSI, long before LSI and pin-count issues.
And, of course, the multiplexing fit naturally with serial architecture.
By the time LSI and LEDs came into play, the architectural 'standard'
had already been set, reduced connection count was an additional
benefit.
Joke-a-side..
If multiplexing really did save power then just
pulsing a
single led would do the same..
Multiplexing of LED displays was intially done, I think, to save
connections. If you think of an 8-digit calculator display (with 7
segmets + a decimal point per digit), that's 64 LEDs, so 64
conenctions
to the display (+ a common return). If you multiplex it, that's 16
connetions, 8 for the segments (one for the top, one ofthe top right
vertical, etc) and 8 to select the digits (one per dgiti).