mirror of
https://github.com/robmcmullen/asmgen.git
synced 2024-06-01 20:41:28 +00:00
134 lines
2.8 KiB
ArmAsm
134 lines
2.8 KiB
ArmAsm
; backing store test, hardcoded for 3x11 apple.png-sized sprite
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;
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; The backing store memory starts from some high address
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; and grows downward in order to facilitate speedier restoring, because
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; there will be different sized chunks to restore
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;
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;
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;
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;
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; needs:
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; bgstore: (lo byte, hi byte) 1 + the first byte of free memory.
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; I.e. points just beyond the last byte
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; PARAM0: (byte) x coord
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; PARAM1: (byte) y coord
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;
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; everything else is known because the sizes of each erase/restore
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; routine will be hardcoded.
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; modification of quinn's column sweep
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; memory needed for this chunk of background:
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; 2: address of restore routine
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; 1: x coordinate
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; 1: y coordinate
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; 33: number of bytes of background to save
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SIZE_3X11 = 2 + 1 + 1 + 3*11
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savebg_3x11
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sec
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lda bgstore
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sbc #SIZE_3X11
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sta bgstore
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lda bgstore+1
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sbc #0
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sta bgstore+1
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ldy #0
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lda #<restorebg_3x11
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sta (bgstore),y
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iny
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lda #>restorebg_3x11
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sta (bgstore),y
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iny
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lda PARAM0
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sta (bgstore),y
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iny
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lda PARAM1
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sta bgline
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sta (bgstore),y
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iny
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savebg_3x11_line
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ldx bgline ; Calculate Y line
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lda HGRROWS_H1,x ; Compute hires row
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sta savebg_3x11_col0+2
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sta savebg_3x11_col1+2
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sta savebg_3x11_col2+2
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lda HGRROWS_L,x
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sta savebg_3x11_col0+1
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sta savebg_3x11_col1+1
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sta savebg_3x11_col2+1
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ldx PARAM0 ; Compute hires column
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lda DIV7_1,x
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tax
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savebg_3x11_col0
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lda $2000,x
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sta (bgstore),y
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iny
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inx
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savebg_3x11_col1
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lda $2000,x
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sta (bgstore),y
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iny
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inx
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savebg_3x11_col2
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lda $2000,x
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sta (bgstore),y
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iny
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inc bgline
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cpy #SIZE_3X11
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bcc savebg_3x11_line
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rts
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; bgstore will be pointing right to the data to be blitted back to the screen,
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; which is 4 bytes into the bgstore array. Everything before the data will have
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; already been pulled off by the driver in order to figure out which restore
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; routine to call. Y will be 4 upon entry, and PARAM0 and PARAM1 will be
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; filled with the x & y values.
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;
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; also, no need to save registers because this is being called from a driver
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; that will do all of that.
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restorebg_3x11
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ldx PARAM1 ; Calculate Y line
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lda HGRROWS_H1,x ; Compute hires row
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sta restorebg_3x11_col0+2
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sta restorebg_3x11_col1+2
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sta restorebg_3x11_col2+2
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lda HGRROWS_L,x
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sta restorebg_3x11_col0+1
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sta restorebg_3x11_col1+1
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sta restorebg_3x11_col2+1
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ldx PARAM0 ; Compute hires column
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lda DIV7_1,x
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tax
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lda (bgstore),y
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restorebg_3x11_col0
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sta $2000,x
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iny
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inx
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lda (bgstore),y
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restorebg_3x11_col1
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sta $2000,x
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iny
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inx
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lda (bgstore),y
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restorebg_3x11_col2
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sta $2000,x
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iny
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inc PARAM1
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cpy #SIZE_3X11
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bcc restorebg_3x11
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rts
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