Ideas for a simple, but somewhat extendable computer bus

Jim Brain brain at
Sun Nov 19 13:56:43 CST 2017

On 11/19/2017 9:08 AM, emanuel stiebler wrote:
> On 2017-11-18 23:48, Jim Brain wrote:
> > Looking at the schematic for the ECB, I cannot find any description of
> > the signals BAI, BAO, IEI, and IEO.  Can anyone shed some light on the
> > function of these signals?
> Here again:
> I have some ECB documentation "somewhere", but I'm moving so it is in 
> one of the 100s boxes somewhere :(
> But the guys on the retrobrewcomputers can help you for sure.
> And yes, I like ECB, it was small & simple, you still can get boards 
> for it, and the DIN conectors I still use ...

I went there already, but the descriptions:

*BAI 1; BAO 1:* Bus Priority In; Bus Priority Out.

*IEI; IEO:* Interrupt Enable In; Interrupt Enable Out.

does not give much clue as to usage, especially as I see that the pins 
are unwired on the backplanes, and require ones to add jumpers to 
connect them.  I understand that they are used to "chain" boards 
toghether in some order, but how and why is left as an exercise for the 

I looked at each of the backplane schematics for guidance, as well as 
looking at various ECB cards (the interrupt card I thought would have 
more detail, but alas, not)


Jim Brain
brain at

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