If the logic would fit in a 16V8, the Atmel ones start at $1.32 at
Digikey. And a 7-segment display is $1.17.
Multiply by 10 displays on a board and it's a ~$65 cost difference in
outfitting the board
There's no reason any of us couldn't do another mezzanine board
though.
Andrew B
On Tuesday, March 4, 2014 12:20:20 PM UTC-8, monahanz wrote:
One more note on this. I had actually considered doing a small GAL
Hex to 7 bit converter (GAL22V10), (the old DM9368 are no longer
available), but again you really cannot multiplex it fast enough --
so you would need 10 of them. Could be on a (larger) mezzanine board
but at $3 each (Jameco) and a new mezzanine layout board etc. I
figure it's not worth it. Utsource
(http://www.utsource.net/ic-datasheet/TIL311-421656.html
<http://www.utsource.net/ic-datasheet/TIL311-421656.html>) sells
TIL's at ~$9. John
-----Original Message----- From: n8ve...@googlegroups.com
<javascript:> [mailto:n8ve...@googlegroups.com <javascript:>] On
Behalf Of David Riley Sent: Monday, March 3, 2014 7:37 PM To:
n8ve...@googlegroups.com <javascript:> Subject: Re:
[N8VEM-S100:2635] Re: A new (V2) version of the S100 Bus System
Support Board
On Mar 3, 2014, at 21:48, Andrew Bingham <abi...@gmail.com
<javascript:>> wrote:
I think the big problem is as John mentioned you need to grab the
data from the address and data buses and output it to the LCD fast
enough to complete the update before the next clock cycle.
Say you're talking about a 24-bit address and 16-bit data, in hex
that is 10 characters. The part of the system talking to the LCD
would have to update it at 120 Mhz in order to be able to update all
10 characters before the next clock cycle (and that's assuming that
you can update 1 full character/clock). Most microcontrollers won't
be up to that task.
That's assuming you want to update it at the bus rate. An LCD can't
possibly keep up with even a fraction of that, not could the human
eye. You could, however, do something along the lines of a 60 Hz
update cycle, which is much more achievable.
Personally, I like the aesthetics of an LED display better, and the
fact that it's updating with the bus gives you an idea of how often
it's showing segments (something you won't get with an LCD).
For replacing the TIL311 displays, I have seen reference to DIP
decoder chips that will decode 4 bits of binary into showing hex on
standard 7-segment displays - 0-9 and A, lower case b, C, lowercase
d, E, F. That's probably the best option for something that will
remain readily available.... Or program a DIP PLD device.
There are certainly lots of hardware decoding devices meant for
7-segment LEDs (and you can make one with a simple CPLD rather
easily). TIL311 style devices are becoming more rare, but I think
they're certainly the best looking ones out there (short of Nixie
tubes, I guess, but that's bordering on silly).
- Dave
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