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

[David Riley <frave...@gmail.com>]

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