Re: Strange 8255 behavior

From: Jeff Laughton <laughton_at_cyg.net>
Date: Sun, 10 Jun 2018 07:50:42 -0400
Message-ID: <20180610075042.Horde.AZjFGa2wwUu8MyYQtvIVetn@www2.cyg.net>
> On 10/06/2018 10:57, André Fachat wrote:
>
>> [...] (like I guess clearing interrupt flags by just reading the flags....).

I believe clearing interrupts by reading the flags is actually a  
feature. It leads to a shorter Interrupt Service Routine because you  
don't have to reset that flag explicitly. But yes you have to pay  
attention or it'll bite you.  :-(


Quoting smf <smf@null.net>:

> 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.

Hmm, well, maybe, but I'm not convinced (although I agree it'd be the  
lesser of two evils).



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

Now *that* is something I can fully agree with!!  :-D
Received on 2018-06-10 14:01:24

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