Re: [stella] Telepahy, Yahtzee, Compumate....

Subject: Re: [stella] Telepahy, Yahtzee, Compumate....
From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx>
Date: Mon, 1 Jan 2001 14:55:58 +0100
> The Compumate doesn't work at all if you don't plug both connectors into
> the joystick ports. It shows vertical lines and makes noise, like when a
> cart isn't working.
> Did you understand why?

That's because the Compumate basically is a nonworking cart without
it's keyboard. ;-) The ROM does constantly check two of the paddle
lines to see if the keyboard is connected. If it doesn't detect the
keyboard anymore, it jumps into an infinite loop and stops working.
The reason for that is that the Compumate does it's bankswitching
and RAM selection through the joystick port! Two of the lines
are used to select any of the four ROM banks. Two other lines
are used to handle the RAM. One line allows you to map in the
2K of RAM, the other line selects between read and write mode.
If the RAM is turned of, the read write line is also used to
trigger the next column on the keyboard to be read, or it is
used to write to the tape interface.

Oh and since you asked, John and I were really thinking about adding
the load and save feature to the Compumate emulation, but haven't
found a good way to implement it yet. ;-)

Ciao, Eckhard Stolberg

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