PET 2001 RAM question

From: Francesco Messineo <francesco.messineo_at_gmail.com>
Date: Tue, 30 Jan 2018 10:25:51 +0100
Message-ID: <CAESs-_yYJya9TTQdYBMnuH-VWNaG6Rax-uQ=Gajiu4UybGun+A@mail.gmail.com>
Hi all,
I'm looking at the 2001 with 2114 RAMs, as always I refer to the
schematics found on zimmers.net.
One thing that I noticed is that the /WR signal to the 2114 RAMs is
qualified with PHI2 (inverted, then N-ANDED with a buffered PHI2), but
otherwise all the RAM's chip selects and 244 buffers are only enabled
depending on the 6502 address bus and I can't find any PHI2
intervention on either the selects or the 244 buffer enabling.
So, just for  my ignorance, why the R/W signal from the 6502 needs to
be qualified on the right phase of the clock and the address bus
doesn't?
Thanks
Frank IZ8DWF

       Message was sent through the cbm-hackers mailing list
Received on 2018-01-30 10:00:03

Archive generated by hypermail 2.2.0.