Microcontroller "PEEKing" into C64 memory?

From: Leif Bloomquist <leif_at_schemafactor.com>
Date: Thu, 21 Jan 2016 11:18:22 -0500
Message-ID: <CAOTCz+HeALvOJJH+Z+sT4QEd3X82tbGoTyaAUEH-twKqWbWiLQ@mail.gmail.com>
Hi all,

I have an idea for a project that would require an external
microcontroller to be able to "peek" into parts of the C64 Memory.

It wouldn't matter where.  I/O1 and I/O2 might be easiest, but some
unused space like $02A7-$02FF could also work and not interfere with
external devices.   Only would need 8 bytes or so.

What would be the easiest way to go about this?

I'm not an electrical guy at all, but my initial concept would be a
dual-port SRAM along with a decoder (74LS138, etc) that signals when
the particular address range is selected (as well as on Write). Then
have the data lines and a few of the address lines connected to the
SRAM that gets written to when that triggers. From there the
microcontroller can read the SRAM from the other port and do its

Would this be easiest, or are there other better ways?

There's also this, a cool project (but total overkill), proves it can
be done:  http://hackaday.com/2014/12/26/dual-porting-a-c64-flash-cart/

(Plan B would be to to have a UART and go serially through the User
Port, but then special software would be needed on the 64, more
involved than just a POKE.)


Leif Bloomquist | leif@schemafactor.com | +1 416-737-2328 | Check out
my blog! http://www.jammingsignal.com

"Every choice, no matter how small, begins a new story." - xkcd

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