CitizenSnips wrote:
I'm trying to stay as true to the original microarchitecture as possible in my design, and have been using this block diagram to do so.
Best of luck with your project!
If you haven't already, you should consider the bidirectional nature of the two sets of pass MOSFET's. An actual 6502 exploits the MOSFET's ability to pass a signal in either direction (as can be seen if you explore various visual6502 simulations).
Directly implemented in silicon, the pass transistors are a shortcut that simplifies the design. Unfortunately that's not the case in the FPGA context. This isn't intended to discourage you. I'm just pointing out that using the original 6502 as your roadmap may drastically complicate matters, contrary to what one might expect.
AFAIK only one of the 19 cores in Garth's list models the pass transistors; all the other cores use unidirectional signal paths, which of course map much more easily to FPGA. The exception is Andrew Holme's core, which he describes here and which is the subject of this forum thread.
(BTW, CitizenSnips, it's not necessary to use third-party sites for posting images. On this forum you have the option of including images as attachements to your post.
)cheers,
Jeff
