Re: Strange 8255 behavior

From: Michał Pleban <*lists_at_michau.name*> Date: Sun, 10 Jun 2018 13:59:01 +0200 Message-ID: <5B1D1285.2020006@michau.name> · lists_at_michau.name

Hello!

smf wrote:

> I assume for cost purposes they don't keep the last output value when in
> read mode, so when you switch back to output mode then zeros is probably
> the lesser of two evils.

That might be the case when you switch from input to output, but when
you "switch" from output to output (i.e. you leave the direction of the
port unchanged, only modifying some other port) it's just ridiculous.

> Trying to replace a mos chip with an intel chip is blasphemy :-)

Guilty as charged :-) But it's for a good reason: there are only very
little 6525's laying around, and if we want to make the 8088 card
accessible to everyone, we had to change to a chip that's readily available.

Regards,
Michau.