LED displays (TIL305, TIL308, etc.)
ethan.dicks at usap.gov
Mon Sep 29 22:48:31 CDT 2008
On Mon, Sep 29, 2008 at 08:42:38PM -0400, Roy J. Tellason wrote:
> On Monday 29 September 2008 18:44, Ethan Dicks wrote:
> > Hi, All,
> > Since one of the first computers I ever got my hands on as a kid (Quest
> > Elf) happened to have TIL311 HEX displays, I've long been fascinated with
> > display technology of that vintage...
> > They still look cool, though, and that's the real point.
> This is neat stuff...
> I built a digital counter for a guy back in 1975, using TTL and displays that
> I bought on Canal St. in NYC. I still have some number of that sort of
> display around, and haven't figured on any particular use for them yet,
> plus some that I've salvaged a bit here and there, some two-digit parts,
Nice. We used to have a short block of surplus stores in Columbus while I
was growing up (I picked up a couple cardcages with "Gorf" arcade game cards
and got them working later), but nothing like Canal St.
> No 7446/7 chips on hand to drive them with, though. Or any of the
> 4000-series CMOS either. :-(
I have one or two of a few different types, but no loose 9368s (only
installed in boards already).
One thought I had for trying to use a reduced-pin-count MCU-based numeric
display was a 7447-type chip on 4-bits of an I/O port, and a 74145-type
BSD decoder on the other half of the port - up to 10 digits easily, or 9
with simple blanking (write 0 to the '145 and don't hang a digit off of it).
Just checking now, it looks like the CD4511 won't render any digits if you
give it an input over "9" (the 7447 has incomplete decoding internally, so
will light various odd segments if you don't stick to 0-9). With a CD4511,
then (and a 74145 or CMOS equiv), one could hook up to 10 digits and just
write "F"s to any positions you wanted to blank.
There used to be a number of interesting digit and segment driver chips
like the ICM7218D (most famously found in Dragon's Lair and Space Ace
scoreboards), but many of them are difficult to find now, and most of
them cost $8 or more new (and still do when you can find them). They
do make things easy, though, as long as they provide enough digits (the
DL/SA scoreboard has 16 total digits and a pair of ICM7218D to drive them).
They are as easy to talk to as a 6522 or 6821 - R/W, register select and
4-bits input - meant to be memory-mapped, but quite easy to talk to on
the other side of a PC parallel port, for example.
Since I have a couple, my only "problem" is that I haven't found an
integrated multi-digit driver chip that drives more than 8 digits
(and using two of the aforementioned driver chips to drive, say, 6+4
digits substantially increases the project cost).
> I was always wanting to get my hands on some of those hex or better yet 5x7
> displays back in those days to play with. Oh well.
Back in the day, I just had two TIL-311s and they were attached to my Quest
Elf. I did take a pair of raised-segment LEDs and hook them up to the
User Port on my PET and wrote a simple interrupt wedge to grab a normally-
unused zero-page byte, and at about 30Hz refresh, blast out a pair of
hex digits. I built it when I was 13-14, but I still have it around
somewhere in the bottom of a drawer.
> Definitely nifty stuff, for sure.
Oh, yeah. So are small textual and graphical LCD and VFD displays, but
there's a real appeal, to me at least, of the soft glow of red LEDs. Not
quite as cool as Nixies, but those evoke memories of a different era.
Ethan Dicks, A-333-S Current South Pole Weather at 30-Sep-2008 at 03:00 Z
South Pole Station
PSC 468 Box 400 Temp -73.7 F (-58.7 C) Windchill -112.1 F (-80.1 C)
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Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
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