Re: Hardware emulation of 6509 using 6502?

From: Dr Jefyll <laughton_at_cyg.net>
Date: Wed, 28 Feb 2018 09:09:16 -0700 (MST)
Message-ID: <1519834156908-0.post@n4.nabble.com>
Jim Brain wrote
> * After not having success with the '245 daughter-board, I wired up a
>     50MHz oscillator in hopes that I could synthesize a proper PHI_IN

Hm, you've reminded me that a Phase Locked Loop is an alternative (and
near-ideal) solution re clocking and the delay inherent in using the 6502's
Phi0 input. Here's an example I'm familiar with, which is tiny and
self-contained -- small enough, I think, for the next rev of your PCB. It
can reproduce the input frequency while also exactly matching the /phase/ of
whatever reference you give it. Very easy to use! (although it does take up
a bit of space on the PCB)
http://www.cypress.com/file/38861/download

Meanwhile, if you want a temporary solution, you can use the flying lead I
suggested earlier (it's just past the halfway point on page 8 of this
thread). You shouldn't have to alter any details, as I wrote the suggestion
while referring to the schematic, not the %$#@*&^% datasheet!  Nice work
catching *that* boner, btw!


BTW I suspect we'll be forced to return to the other issue -- tristating the
mobo when the CPU is reading the ports at 0000/0001.

-- Jeff





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