RE: Cat Box

> > So we would have to have a set of latches to pretend they were the
> switch
> > matrix. Not too tough.
> > And we would have to have a set of latches to pretend they were the
> > display's. Once again not to bad.
>
> Why are any latches needed?
I assume (not knowing just how the logic board works) that it poles the
values of the switches as it needs them. As such unless we want to rewrite
the CB code we would need to make the switch states available to the CB CPU
all the time. That is why I thought it might work to just put a flip flop
out there to pretend it was a switch that we set through the PC parallel
port (with associated multiplexing ect).

Same deal with the display outputs. We need to hold there states so that
the PC can get at them when it needs them.

If we could figure out a way to get a handshake of data from the PC to CB
then we could avoid the buffering of the various signals completely. But I
don't understand the CB logic board / code well enough to figure out how to
do that.

I figured as we don't have that many i/o's on the PC PP do to all the
switches / displays at once we would have to do a loop of:

                Let user select function on PC
        Update switch settings latches as needed to do this function (or
step of function)

        Read in the display
                Translate display data to screen in some manner (mucho easy
on my part).

The nice thing about doing it with the PC is if we have to do something that
takes a few steps (like setting up the test pattern in the vector display as
described in 20 steps in the CB manual) it could all be automated with one
menu selection.

> Just send the signals from/to the Parallel Port. Some line
> drivers (LS244) may be needed to drive the data to the PC. I made that
> mistake with the Exorcisor.
The line drivers were kind of a given yea. The PP can only sink/source 3 or
4 TTL loads per line I think. I have a PP programming manual around
somewhere I am going to have to dig out.
>
> > The XOR's for the probes are still needed but could perhaps be moved
> into
> > the "chip". Joe?
>
> I think so....what do those actually do? I noticed those
> on the schematic but just never paid any attention? Are they to
> invert the polarity of signals in certain modes?
>
Looking at the Schematic they appear to just cause the change in data to be
based on either the rising or falling edge of the signal. If you want to
check the schem yourself it is the top right part of figure 11.2 (page 40).

One general comment to all. I am a windows programmer. My DOS display
coding is VERY rusty as such I will be doing any code I write in windows.
This may or may not be a problem for anyone else.

I will be glad to help anyone out there port any code I do for any PC
interfacing I do to anything else but no promises on how easy it will be.

David
Received on Fri Jul 24 15:38:46 1998