Re: [N8VEM: 14731] Re: DIY ISA backplane

Unfortunately I couldn't find a standard decoder that would do all 16 digits for the JR-IDE and the IBM BIOS did use hex numbers. Had to resort to a ATF1502 to do both hex digit decode and PWM LED drive and sync.

One nice feature I added though were the two decimal points on the hex display are driven by the Q and Q' of a T-FlipFlop clocked by A7. So it's a sort of CPU activity monitor. You can characterize a lot of what the CPU is doing by watching it.

On September 26, 2012 at 2:12 AM Sergey <sk...@gmail.com> wrote:

> Yes, post codes display is definitely a nice idea... and it is not too
> complicated to build... something like one 74LS688 for address decode
> a pair of 74HCT4511 7-segment latches/decoders/drivers, with matching
> LED displays and resistor arrays.
> Unfortunately 74HCT4611 will not decode numbers above 09h, but
> fortunately we define what post codes to use :-)
>
> Thanks,
> Sergey
>
> On Sep 25, 10:50 pm, opticpow <w...@ingram.net.au> wrote:
> > Hi Wayne,
> >
> > I think your idea of having the "post card" build into the back plane would
> > be a good idea. I think the FDC would be better as a card to allow more
> > flexibility.
> >
> > Cheers,
> >
> > Wayne.
> >
> >
> >
> >
> >
> >
> >
> > On Wednesday, September 26, 2012 12:54:49 PM UTC+10, Wayne Warthen wrote:
> >
> > > Hi Sergey,
> >
> > > I would certainly be interested in the backplane as well. Including
> > > serial ports and FDC seems useful, but I don't think it is critical since
> > > those are easy to add with adapters. The only other idea that occurred to
> > > me was possibly including a pair of POST diagnostic HEX digit leds. It is
> > > certainly not a big deal to me, just an idea.
> >
> > > The only critical thing to me is that it be ATX case mountable.
> >
> > > Thanks,
> >
> > > Wayne
> >
> > > On Tuesday, September 25, 2012 12:43:38 PM UTC-7, Sergey wrote:
> >
> > >> Hi,
> >
> > >> Several people asked me about getting an ISA back plane. While it is
> > >> possible to buy one, some folks would like to build one themselves.
> >
> > >> So I am wondering how many people would like to build one?
> >
> > >> Also I would like to collect various ideas for making the backplane.
> >
> > >> Here is what I have in mind so far:
> >
> > >> - Minimally sized Micro ATX board (9.6" x 6.7" or so). It is possible
> > >> to make the board even smaller, only using the PCB space needed for
> > >> connectors and other components, but yet keep the ATX - compatible
> > >> mounting holes.
> > >> - 5 or 6 ISA slots. Note that Micro ATX only allows 4 slots, so if
> > >> using a case only 4 slots will be exposed on the back side. But still
> > >> it should be possible to use the remaining slots for cards that don't
> > >> have connectors on the back side, for example the XT-IDE card.
> > >> - ATX power connector and power on circuit (so it will work with a
> > >> momentary switch normally found in ATX cases)
> > >> - Minus 5V regulator (convert -12V to -5V). Most modern ATX power
> > >> supplies don't provide -5V (it is optional), but yet some ISA cards
> > >> use it. This circuit could be optional with a jumper to select -5V
> > >> source (ATX power supply or the backplane regulator)
> > >> - Onboard FDC and UART... maybe a couple of UARTs. I am not sure about
> > >> this one... an alternative would be making an FDC/UART ISA card, which
> > >> is more universal approach. I this case it is possible to provide two
> > >> DE9F serial port connectors with 5x2 headers connected to them (for
> > >> example to plug the XT-IDE V2 serial interface).
> >
> > >> Any suggestions?
> >
> > >> Thanks,
> > >> Sergey
>
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