RE: 6510FPGA Suggestions?

From: Bil Herd <>
Date: Mon, 26 Aug 2013 10:01:49 -0400
Message-ID: <>
Yes a single clock domain is best, only the global clock should appear on
the clock input of a flipflop/register and the enable can be applied
asynchronously.  A lot of floorspace in the bigger FPGA's is dedicated to
Phase Lock Loops and support so that the clock domain can be expanded and
the same clock domain can extend to the internals of other FPGA's by putting
their PLL in a feedback loop of the original.  Tweaking for cable and
waveguide propagation to realign the clock is also possible using the PLL as
a Delay Locked Loop.

I did a video system a long time ago that had 24 custom cameras, a DSP
engine, and a fiber concentrator, interconnection mesh and there was a
single clock that drove the whole thing (Approx 500,000 LE/gates).  I used
to tap  on the TCO knowing that the vibration was effecting the clocks for
devices 50 foot in every direction.

-----Original Message-----
[] On Behalf Of Mark McDougall
Sent: Monday, August 26, 2013 9:44 AM
Subject: Re: 6510FPGA Suggestions?

You are completely wrong. The best approach is a fully synchronous design
with a clock enable.

Sent from my ASUS Pad

Istvan Hegedus <> wrote:

>I have been investigated these cores too and found FPG64's 6510 code
>the closest implementation. I am currently playing experiments with it
>and one drawback is that it uses fast clock (33Mhz) and slows the CPU
>down with the enable signal. This however is needed in order not to
>violate the clock domain of the whole FPGA64 design. It can be driven
>with slower clock speed too but it is not a good concept to have
>different clock speeds in your FPGA.
>-----Original Message-----
>Sent: Saturday, August 24, 2013 12:41 AM
>Subject: 6510FPGA Suggestions?
>Since for some time I am walking circles around the FPGA/CPLD
>bandwagon, I thought it might be time to have a closer look. I checked
>opencores and tried to decide where to spend some money (Altera, Atmel,
>Xilinx, ...?) that would be able to implement a 6502 and an I/O port
>together with some RAM and ROM modules. My n00b questions to the more
>experienced fellows:
>- how many kgates can be needed for something like I mentioned above?
>- what would be the best h/w platform/vendor and why?
>- what is the most complete/reliable 6502 core to use as starting point?
>- what can you suggest or warn about?
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1jj   qi

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Received on 2013-08-26 15:00:03

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