Subject: Re: [stella] Supercharger Bankswitches and RAM access!|
From: Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx (Eckhard Stolberg)
Date: Sat, 15 Mar 1997 18:45:20 +0100
><< >How is the value determined using indirect-x and indirect-y? > >How is the address determined using indirect-x and indirect-y? > > The value is accessed address minus $F000 > The address to write to is the address that is accessed 3 or 4 cycles after > the access to $F0xx. > >> > >OK, lets look at the following > >cmp 1000 >nop >lda (2000),y // don't worry about the nonsense addresses > // at location 2000 is 1234 stored > // y=6 > >is that like a BASIC: > >poke 0,2000 >poke 0,2006 >poke 0,1240 >? It would be Type Mismatch Error, because indirect-y addressing only works when the pointer is stored in the zeropage. But if you do CMP $F000,X CMP ($80),Y (no NOP, because this addressing mode takes more cycles) it would write the value stored in X to address 1240. Ciao, Eckhrad Stolberg -- Archives available at http://www.biglist.com/lists/stella/archives/ E-mail UNSUBSCRIBE in the body to stella-request@xxxxxxxxxxx to be removed.