Re: 16 MB REU clone

From: Marko Mäkelä (
Date: 2001-08-22 12:01:15

On Wed, 22 Aug 2001, Rainer Buchty wrote:

> But since the C64 already needs a few seconds to be fully initialized
> the serial method shouldn't be noticeable anyway.

Unless the chip is used as a buffer between the 5-volt cartridge port and
the low-voltage memory chips, and the on-cartridge ROM is used for booting
the C64.

It seems that the smallest chip in this Xilinx Spartan-II family (XC2S15,
100 pins) could otherwise do the job.  I wonder if there are easy-to-use
serial ROM chips that could be programmed multiple times.  The XC17S00A
family is one-time programmable.  There is the XC18V00 family, but
apparently it is meant for the Virtex family (XC2V00 series) that might
not have 5-volt tolerant chips.

How long does it take to initialize the logic?  The XC17S15A PROM meant
for the XC2S15 CPLD can hold 197696 bits of data.  The maximum speed seems
to be 10 megabits per second.  At that speed, it would take 20
milliseconds to boot the logic.  That should be acceptable.  The DONE
signal could even be wired over a diode to the RESET input of the
cartridge port, so that the system cannot start up too early.


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