On Tue, 3 Mar 1998, [ISO-8859-1] Marko Mäkelä wrote: > Hello Ruud, > > > But my idea has one big unsolved problem yet: how can I read data? Maybe > > one of you knows how the SID behaves when you read a write-only > > register. > > Why don't you experiment yourself? If I remember correctly, the SID is > quite special, because the write-only registers (at least some of them) > hold the newly written value for some time. Yes, all of them work the same. $D400 - $D418 ; $D41D - D41F >Another possibility would be > that it returns "random" data, i.e. the same as $de00-$dfff when no device > is connected. But I vaguely remember writing a test program that wrote > and read back the write-only SID registers. They retain the written value for a few microseconds. Something like that. ex. STA $D400 LDA $D400 Always works. Acc. does not change. Same too: STA $D400 LDA $D40D ETC... Note, when the SID is not producing any sound, these registers all always return $00.
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