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RE: [N8VEM-S100:2635] Re: A new (V2) version of the S100 Bus System Support Board

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) sells TIL's at

-----Original Message-----
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On
Behalf Of David Riley
Sent: Monday, March 3, 2014 7:37 PM
To: n8vem...@googlegroups.com
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 <abin...@gmail.com> 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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