Subject: [stella] The ol' Playfield Swap From: Schwerin <schwerin@xxxxxxxx> Date: Sun, 21 Feb 1999 21:18:17 -0500 |
Can you look at this code snippet for me from an ongoing project? I have the Playfield in reflect mode, and I'm not using PF0. I want to make sure the PF2 swap occurs on the right machine cycle. I'm just about ready to run the full version on emulation. Here is the snippet..... Draw_Screen: lda DrawH beq V0 ;branch if DrawH = 0 H0: ; [70] from previous sta WSYNC ; [70] + 3 ; [73] ; sleep for 2 cycles. lda FieldH00 ;[00] + 3 sta PF1 ;[03] + 3 lda FieldH01 ;[06] + 3 sta PF2 ;[09] + 3 lda FieldH02 ;[12] + 3 ; kill some time pha ;[15] + 3 pla ;[18] + 4 pha ;[22] + 3 pla ;[25] + 4 pha ;[29] + 3 pla ;[32] + 4 pha ;[36] + 3 pla ;[39] + 4 lda FieldH02 ;[43] + 3 ;[46] sta PF2 ;[46] 46,47, *48* (swap on 3rd cycle of sta dp) lda FieldH03 ;[49] + 3 sta PF1 ;[52] + 3 dec ScanLine ;[55] + 5 beq Exit0 ;[60] stop drawing! dec DrawH ;+2 [62] + 5 bne H0 ;[67] + 3 {taken} ;+ 2 {not taken) ;[69] ;DrawV is non-zero here... V0: sta WSYNC ;[69] + 3 ;[72] ;sleep for 3 cycles... lda FieldV00 ;[00] etc.................. -Andrew Schwerin -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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