Re: Carte Blanche and Apples other than 2e

On Oct 4, 1:59 am, Alex Freed <alex_n...@xxxxxxxxxx> wrote:
It came to my attention that the image selection from a keyboard doesn't
always work right on a 2GS. I also know that it doesn't work on a 2+.
This is not exactly a "bug" - rather the implementation is model specific..

To get the keyboard input CB monitors the Apple bus as it appears on the
slot connector. If it detects a read from $C000 and the high bit of the
data is set it is taken as a keyboard pressed event. Now it gets a bit
technical. The signals available on the bus are Q3 and PH0 among others.
In most cases the data is valid on a falling edge of the Q3 signal
during PH0 high phase of the system clock. This is fine for latching the
keyboard access on a 2+. Unfortunately the 2e uses a different design
and the keyboad data becomes valid later than that. It also stays valid
longer and can be latched on a falling edge of the ph0 itself. Since the
vast majority of the A2s are of the 2e variety I chose to use the 2e
timing in the default design.
If the 2+ timing is preferred it is a single Verilog line change.
Unfortunately a fix that would work for *both* is not quite as simple.
Not terribly hard either - just make a state machine running off the 50
MHz system clock to latch the data somewhere at the right moment that
works for both 2+ and 2e. Chances are it will also work for the GS.

I will probably do it eventually (if nobody does it before I do) but it
is  not a first priority.

As for the VGA for GS the current design will support the standard video
modes but not GS specific ones and not even the double-hires. Can be
done but not the top priority either.

-Alex.


Alex,

Is the IIgs support going to become a higher priority for you at some
point? I realize that the first lot of cards have sold out, but I
would have purchased one if I knew that you had short-term plans to
support the IIgs video modes. I really have no interest in a CB for
my IIe because games work fine on a 14" composite monitor... whereas
the IIgs sitting on my desk is begging to be connected to a VGA
monitor or modern LCD :)

Just a question....



.

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