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| From: Richard Atkinson
Date: 1999-01-19
Subject: Re: Check SID Version !
|
On Tue, 19 Jan 1999, TFSS Of The GPS wrote:
> Hello Mindenki !
>
> Tehat valahogy igy nez ki az emlitett SID tesztelese ?
Hmm. Not too sure what that says, so I'll ask my own questions about the lovely bit of self-modifying code below:
What is returned in the accumulator for an old (6581) SID chip, as compared with a new (8580) chip? Presumably it's got something to do with how the write-only frequency registers respond after they've been written to, but... ?
Richard
>
> ;---------------------------------------
> ; CHECK C64 SID VERSION 1.00
> ;
> * = $2000
> ;
> SIDBASE = $D400
> ;
> CHKSID PHP
> LDA $01
> STA MEMCFG+$0001
> CLD
> LDA #$37
> STA $01
> LDA #$FF
> STA $D400
> WAIT1 LDA $D400
> WAIT2 LDA $D400
> WAIT3 LDA $D400
> WAIT4 LDA $D400
> WAIT5 LDA $D400
> WAIT6 LDA $D400
> STA SIDVER+$0001
> MEMCFG LDA #$00
> STA $01
> SIDVER LDA #$00
> PLP
> RTS
> ;
> ;---------------------------------------
>
>
> Bye !
>
>
> TFSS OF The GPS.
> --this message went through the plus4@c64.rulez.org emailing list---
>
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