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base:opening_the_top_bottom_borders

Opening the top and bottom borders

This is a clever trick for you to try on the C64. Demos in the 1980's and 1990's and probably still today use the opened borders technique. I am going to show you how to do a simple border opening technique in ACME crossassembler format.

;Opening the top + bottom borders
;inside an IRQ interrupt player

         !to "borders.prg"
         
         * = $0810 ;SYS 2064 to run it
         sei
         lda #$02
         sta $d020
         lda #$00
         sta $d021
         lda #<irq1
         sta $314
         lda #>irq1
         sta $315
         lda #$7f
         sta $dc0d
         lda #$1b
         sta $d011
         lda #$01
         sta $d01a
         cli
         jmp *
irq1:    inc $d019
         lda #$00
         sta $d012
         lda #$00
         sta $d011
         lda #<irq2
         sta $314
         lda #>irq2
         sta $315
         jmp $ea7e
irq2:    inc $d019
         lda #$fa
         sta $d012
         lda #$1b ;If you want to display a bitmap pic, use #$3b instead
         sta $d011
         lda #<irq1
         sta $314
         lda #>irq1
         sta $315
         jmp $ea7e
base/opening_the_top_bottom_borders.txt · Last modified: 2015-04-17 04:33 (external edit)