=EF=BB=BF

Hi Craig,

I did res= pond to the shop email, but it didn't get through.

I would like black, or red. It doesn't reall= y matter. If you have a set already printed then that would be awesome= . I can't get anything economically printed here, and don't have= my own facilities, so paying the extra for postage is totally ok.

I don't have the capacity to progr= am 8755 devices. I am happy to on-post an 8755 if you include it in th= e package to somebody here in Australia if that's helpful. No charge.&= nbsp; I appreciate your work, it has inspired me to do lots more with the ST= D bus.

Doug

On Thu, 19 Dec 2024, 4:51=E2=80=AFam SBC-85, <craig@sbc-85.com> wrote:

Hi Doug,

I see you order= ed a set of card guides for the std backplane. What color do you want? =

Also, can you program 8755 eproms? There is someone i= n Australia that needs one.

Regards

Craig

On Jan 31, 2024, at 2:54=E2=80=AFAM, Doug Jackson <doug@doughq.co= m> wrote:

=EF=BB=BF
Hi Craig,

I feel like a complete idiot - I had the ground pin of t= he decoder (U2) in my card bent under the package, open circuit.
<= br>
As soon as I connected it to ground, the circuit behaved beaut= ifully..

Now to populate the 7303 reproduction (the= boards arrived today :-) )

Kindest regards,<= /div>

Doug Jackson

em: doug@doughq.co= m
ph: 0414 986878

Follow my amateur r= adio adventures at vk1zdj.net

<= /div>

On Wed, 31 Jan 2024 at 20:53, Doug Jackson <doug@doughq.co= m> wrote:
<= div dir=3D"ltr">Hi Craig,

I have been tearing my hair out= with the 8085 CPU board, and I suspect that there is a small issue wit= h decoding IO/M* for use as a IOREA* signal.

The CP= U simply buffers IO/M* and passes it out as being IOREQ* on the STD bus.

I have designed a simple Triac output card that uses I= OREQ* as an IO request line, and it is randomly toggling. A trawl thro= ugh the datasheets shows this:

<image.png&g= t;

It seems you have to see S0 or S1 go l= ow before you can believe that IO/M* is an I/O signal.

<= div>I also spotted the beauty on the board:

<image.png>

It looks like you in= advertently grounded S0 and S1 through the DB9 connector, but a quich c= heck with a multimeter suggests that they are open.

I have to double check the Gerbers, but it looks like I have to add ad= ditional logic to validate IOREQ* before it leaves the CPU card.
<= br>
This is the decode logic I have used - which I can't immediate= ly spot anything weird with:

<image.png>=

Have you noticed anything interesti= ng with I/O cards?

Kindest r= egards,

Doug Jackson

em: <= a href=3D"mailto:doug@doughq.com" target=3D"_blank" rel=3D"noreferrer">doug@= doughq.com
ph: 0414 986878

Follow my a= mateur radio adventures at vk1zdj.net