Re: DIY ISA backplane

[Sergey <skis...@gmail.com>]

For whatever reason I clicked on 'Reply to author' button, so Martin
and I had an e-mail conversation :-)

Anyways, here is the brief update:

- I am reluctant to use any of hexadecimal 7-segment decoders because
they are no longer in production
- I proposed two solutions:
1) One can use prototyping space on the backplane board to implement
display decoder of his choice. It will be possible to reuse the
address decode logic. The disadvantage is that it may result in many
various implementations, which could be difficult to support.
2) Use a 74LS573 latch (instead of relying on the built-in latch in
74HCT4511), support a variety of decoders configurable with a couple
of jumpers on pin 3 and 5 (74LS47, 74LS48, 74LS247, 74LS248, DM9368,
CD4511, 4311, D346D, etc.), have a jumper for connecting common
display pin either to VCC (for common anode drivers/displays) or to
the ground (for common cathode drivers/displays). Some of these
drivers have current limiting circuits on outputs, in this case jumper
wires can be installed instead of the current limiting resistor
arrays.

The second option looks like a more universal solution, but it adds
some complexity - an additional IC and 3 jumpers.

Note: While 74LS47/48/247/248 are not hexadecimal decoders, they
display distinct figures for values A-E and a blank for F, so it is
possible to derive the displayed digit by looking at the datasheet.

Thanks,
Sergey

On Oct 4, 12:20 am, Martin Lukasek <martin....@artax.cz> wrote:
> Hi Sergey.
>
> good work, I like the idea of blinking DP on A7 activity. I would prefer to use some displays capable of HEX decoding (displaying A..F). There is a possibility to use direct latched and ecnoded displays such as HP 5082-7340 or TIL311 or there are decoders such as D346D, DM9368, ICM7212, MC14495, 4311, some of them would need latch such as 74HCT573.
>
> I would also appreciate one more 2-pin header for reset, so it would be possible to connect reset to the CPU board as well as mainboard reset button and case reset button.
>
> Best regards
>
> Martin
>
>
>
>
>
>
>
> -----Original Message-----
> From: n8...@googlegroups.com [mailto:n8...@googlegroups.com] On Behalf Of Sergey
> Sent: Thursday, October 04, 2012 8:17 AM
> To: N8VEM
> Subject: [N8VEM: 14778] Re: DIY ISA backplane
>
> Hi,
>
> I uploaded the current version of ISA Backplane schematic to Wiki:http://n8vem-sbc.pbworks.com/w/file/59538666/ISA%20Backplane%20-%20Sc...
>
> Current features:
> - MicroATX compatible backplane with 8 ISA slots (4 slots are accessible from the back side). I added two mounting holes for additional support.
> - ATX power control circuit
> - On-board port 80h POST diagnostic display
> - A header for the serial port
> - -5V voltage regulator. This is optional only in case you have an ISA card that requires -5V and an ATX power supply that doesn't provide it.
> - LEDs for each power rail
> - Many bypass capacitors - generally one per slot per rail. These are optional :-)
>
> Please review and give me some feedback :-)
>
> Thanks,
> Sergey
>
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