> Well, for a simple 2k or 4k game, it's extremely simple. Address lines A0
> through A11 from the 6507 connect directly to the corresponding pins on the
> rom.
do data lines D0-D7 also connect directly to the pins?
> Remember that for the roms used, the chip enable line (CE) and the output
> enable line (OE) are active when they are high. For a standard eprom,
> (a 2716, for example) these lines, /CE and /OE are active low.
>
> With this in mind, A12 connects directly to the rom's CE pin. Or, if an eprom
> is used, A12 runs through an inverter to connect to the /CE pin. The output
> buffers are permanently enabled for both versions (CE = VCC or /CE = GND).
>
> And that's it!
obviously this has something to do with the fact that the atari 2600 can address
only 13 bits of memory :P but it seems if i were to ever produce a circuit of this
kind,
it goes without saying i would have to use an eprom, doesnt it?
> For bank switched games, it's a little more complex. Everything above still
> applies. But there are extra address pins on the rom, A12 through A(n).
> An address decoder is used to detect an access to a "hot address". When a
> hot address is detected, the decoder sets the extra address pins to the
> appropriate values, based on the bankswitching method being used.
>
> I can go into more detail on bankswitching if needed...just ask! But everyone
> should read Kevin Hortons Bankswitching Document first. It's available in
> several places on the 'net.
>
> I hope this helps!
i would imagine bank switched games are a little more complex, given the fact that
they may use several rom chips or even ram on the circuit board...
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