Re: PET 2001/2001N can "write" to ROMs

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Tue, 23 Apr 2019 06:22:33 +0200 Message-ID: <cfa4044d-2e69-fb2b-1e87-65e395e9c8e7_at_laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 4/22/19 10:14 PM, Francesco Messineo wrote:
> Hi all,
> Ok, the subject is a pun, but write is in double quotes anyway. I was
> wondering why the PET (at least the 2001 and 2001N, the ones I have),
> leave the ROMs selected during a write cycle on ROM space. This of
> course makes a data bus contention because the selected ROM will drive
> the data bus and the 6502 will drive the data bus too since it's on a
> write cycle.
> I wonder if this can be a factor in the high failure rate of the old
> 6540s and the newer 2332/2316.

No, NMOS outputs cannot be damaged if they work against each other.

  Gerrit