> While I was making my cart, I put a frequency counter on A12 and got about
a
> 1Mhz for access. I now this isnt the best way to do it, but it was enough
for
> me to realize that there was no way my microcontroller was going to be
able to
> make it. Remember that some microcontrollers take multiple clock cycles
per
> instruction. I was running at 20MHz but, at 4 cycles per instruction I
was
> really at 5MHz. Thats at best 5 instructions per cart read! Not enough
time
> for me. I looked into CPLDs. I have always been afraid of them, but
after a
> little research they are a piece of cake to use. Look into Xilix XC9500
> series. The design software is free and I found a tutorial at
http://www.al-
> williams.com/pbx84.htm. I even ended up buying the al williams
development
> board and programmer (which is incredibly cheap compared to anything else
I
> could find). Their programmer works with the Xilix software. If I can
figure
> it out, anyone can.
I don't think you really need a full blown FPGA like the mentioned Xilinx
XC9500 to do bank-switch emulation in hardware. Some of the simple schemes
(F6, F8, FA) can easily be implemented using a cheap Programmable Gate Array
like a PAL20V16. I haven't tried though, but you can try yourself. Get
yourself some VHDL compiler and select a PAL20V16 or GAL20V16 as target
architecture and check if your code can be synthesized in one of these.
Shouldn't be too hard.
With kind regards,
Matthias
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