8 Dec
2007
8 Dec
'07
4:44 p.m.
------------Original Message:
Date: Sat, 8 Dec 2007 18:30:43 +0000
From: Ethan Dicks <ethan.dicks at usap.gov>
Subject: Re: GAL16V8 as a modern substitute for a 7447?
On Sat, Dec 08, 2007 at 08:12:30AM -0800, Peter C. Wallace wrote:
On Sat, 8 Dec 2007, Ethan Dicks wrote:
Right.
Has anyone here worked with or ever plotted
silently to create a moderish
7-segment decoder/driver from a GAL16V8?
IICRC the 16V8 does not have buried registers so you will lose the 4 of the
output pins (for the counter) that you needed for the 7 segment outputs If you are using sockets, a 5V or 3.3V (cheaper) 44
pin PLCC CPLD might be
a better solution, plus they are easier to program. A X9572XL will probably
do 4 decades of count/decode for about $2.00
That is not feasible. I need 7 or 9 decades of count/decode, and I happen
to have an abundance of GALs and a GAL programmer. If it comes down to a
CPLD-design, I'll probably throw in the towel and use an AVR microcontroller
and perhaps a real 74LS47 or 74LS247 to lower the I/O requirements a touch.
I was just musing about what it might take to put it all in hardware
rather than a combination of hardware and firmware. Using an MCU makes
the entire problem trivial.
Thanks,
-ethan
-----------------
--------------Reply:
Well, since it started one of "those" discussions here as usual anyway,
what's wrong with a 74143?
mike
8 Dec
8 Dec
5:35 p.m.
On 8 Dec 2007 at 19:44, M H Stein wrote:
That is not feasible. I need 7 or 9 decades of
count/decode, and I happen
to have an abundance of GALs and a GAL programmer. If it comes down to a
CPLD-design, I'll probably throw in the towel and use an AVR microcontroller
and perhaps a real 74LS47 or 74LS247 to lower the I/O requirements a touch.
Any need to have a separate decoder for each digit? I wonder if an
alternate approach of using a single BCD-to-7 decoder, multiplexing
the displays and simply concentrating on the counting end.
Just a thought--certainly if I were running this with a PIC or an
AVR, I'd definitely give it some thought.
Cheers,
Chuck
9 Dec
9 Dec
5:11 a.m.
On Sat, Dec 08, 2007 at 05:35:00PM -0800, Chuck Guzis wrote:
On 8 Dec 2007 at 19:44, M H Stein wrote:
> That is not feasible. I need 7 or 9 decades of count/decode, and I happen
> to have an abundance of GALs and a GAL programmer...
Any need to have a separate decoder for each digit? I
wonder if an
alternate approach of using a single BCD-to-7 decoder, multiplexing
the displays and simply concentrating on the counting end.
No requirement, it just keeps the design simple (lots of repetition
of nearly identical digits).
Just a thought--certainly if I were running this with
a PIC or an
AVR, I'd definitely give it some thought.
My AVR plan would be a Tiny2313 and a 7447, probably (need enough I/O
pins for 7 or 9 column drivers plus 4-bit BCD row output plus a button
or two or a serial input). I have the LEDs on hand, already mounted
behind red plexi (thus the desire not to move to TIL311s), and I happen
to have a few Tiny2313 and 90S2313 AVRs with me. I'd just need to pick
up a 7447 or 74247 (I left mine at home, but can have a handful
shipped).
I was hoping to do this in hardware, since once the soldering is done,
it's done, but obviously, an AVR MCU would lead to about the minimum
part count possible. If I had a spare ATMega8, I would have so many
I/O pins available that I wouldn't even need the 7447.
Thanks, everyone, for the suggestions. I have a lot to mull over,
especially to see if it's possible to jam a counter and decoder in
the same GAL. If that turns out to be unfeasible, I'll probably
quit trying to make it 100% hardware and go with the MCU.
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 9-Dec-2007 at 13:00 Z
South Pole Station
PSC 468 Box 400 Temp -23.4 F (-30.8 C) Windchill -45.7 F (-43.2 C)
APO AP 96598 Wind 9.3 kts Grid 17 Barometer 675.9 mb (10783 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
8 Dec
8 Dec
6:57 p.m.
M H Stein wrote:
Well, since it started one of "those"
discussions here as usual anyway,
what's wrong with a 74143?
Indeed, there are also several 4000-series CMOS counter-latch-decoder-driver
combo ICs (4026,4033,40110), as well as some multi-decade versions
(74C925,926..) which I would guess would fill the bill.
(..but I'm guessing the problem is they're not in stock at the South Pole :) )
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