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From: Pigmy (all posts)
Date: 2000-07-25
Subject: Re: Interrupts

> I have a question too about this topic. I asked half a year ago, but
> nobody aswered it properly. What happens, when I write back values to
> $FF09? I found in several programs, that this register is cleared
> when _ANY_ value is written. (At least many of the programs are
> working on this way.) Is that true?
>
> Eg: ASL $FF09 - clears the requests, besides it is working like:
> read $FF09, eg.:$82 (irq request), then shift left: $04, and write
> back.

As I remember, only those bits are cleared in $FF09 which are set in the value. E.g.: $FF09 contains $12 and you put $10, then it will contain $02... Am I right?

Pigmy