Minimise performance issues of None Maskable Interupt
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hugova
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1 changed files with 93 additions and 66 deletions
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@ -1,82 +1,109 @@
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.scope STARTUP
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;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
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;;Settings positions
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CR1 = $d011; ;Graphic settings
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VIC_bank_settings = $DD00 ; Vic position
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Screen_RAM_settings =$D018 ;Screen RAM position relative to VIC
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;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
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;; Settings positions
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CR1 = $d011; Graphic settings
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VIC_bank_settings = $DD00 ; Vic position
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Screen_RAM_settings =$D018 ; Screen RAM position relative to VIC
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;;########## VIC_BANK ################
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;;# BITMAP | $4000 -$5F3F
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;;# Unused? | $5F3F - $6000
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;;# SCREAN RAM (color) | $6000 -$63E7
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;;# Unused? | $63E8 - $7FFF
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;;#
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;;####################################
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;;########## VIC_BANK ################
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;;# BITMAP | $4000 -$5F3F
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;;# Unused? | $5F3F - $6000
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;;# SCREAN RAM (color) | $6000 -$63E7
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;;# Unused? | $63E8 - $7FFF
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;;#
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;;####################################
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;;Memory positions
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VIC_bank = $4000
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VIC_bank_end = VIC_bank + $3FFF
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;; Memory positions
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VIC_bank = $4000
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VIC_bank_end = VIC_bank + $3FFF
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Bitmap = VIC_bank
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Bitmap_end = $5F3F
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Bitmap = VIC_bank
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Bitmap_end = $5F3F
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Screen_RAM = $2000 + VIC_bank
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Screen_RAM_end = Screen_RAM + $03E7
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Screen_RAM = $2000 + VIC_bank
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Screen_RAM_end = Screen_RAM + $03E7
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Character_generator_ROM = $D000
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Character_generator_ROM = $D000
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;;Free upp memory
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;;https://www.c64-wiki.com/wiki/Bank_Switching
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;;
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;;Sets grafic mode [Standard bitmap mode]
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;;https://www.c64-wiki.com/wiki/Standard_Bitmap_Mode
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LDA #%10111111 ; ECM = False
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AND CR1
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STA CR1
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;; Free upp memory
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;; https://www.c64-wiki.com/wiki/Bank_Switching
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LDA #%00100000; BMM = True
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ORA CR1
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STA CR1
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;; Sets grafic mode [Standard bitmap mode]
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;; https://www.c64-wiki.com/wiki/Standard_Bitmap_Mode
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LDA #%10111111 ; ECM = False
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AND CR1
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STA CR1
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;;Set VIC bank to bank 1
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;;https://www.c64-wiki.com/wiki/VIC_bank
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LDA #%11111110 ;bit_0 = False
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AND VIC_bank_settings
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STA VIC_bank_settings
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LDA #%00100000; BMM = True
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ORA CR1
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STA CR1
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LDA #%00000010; bit_1 = True
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ORA VIC_bank_settings
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STA VIC_bank_settings
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;; Set VIC bank to bank 1
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;; https://www.c64-wiki.com/wiki/VIC_bank
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LDA #%11111110 ;bit_0 = False
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AND VIC_bank_settings
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STA VIC_bank_settings
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;;Set Scren-RAM to offset 8 ;https://www.c64-wiki.com/wiki/53272 (offset is 8k byte = 1024*8-ich)
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LDA #%10001111 ; bit_6 =bit_5=bit_4 = Falsw
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AND Screen_RAM_settings
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STA Screen_RAM_settings
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LDA #%00000010; bit_1 = True
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ORA VIC_bank_settings
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STA VIC_bank_settings
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LDA #%10000000; bit_1 = True
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ORA Screen_RAM_settings
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STA Screen_RAM_settings
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;; Set Scren-RAM to offset 8 ;https://www.c64-wiki.com/wiki/53272 (offset is 8k byte = 1024*8-ich)
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LDA #%10001111 ; bit_6 =bit_5=bit_4 = Falsw
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AND Screen_RAM_settings
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STA Screen_RAM_settings
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;;Paint the bitmap black. More bitmap: https://www.c64-wiki.com/wiki/53272, https://www.c64-wiki.com/wiki/Screen_RAM#Moving_of_screen_RAM
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Mov_16 B_start, B_start + 1, #<VIC_bank, #>VIC_bank
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Mov_16 B_end, B_end + 1, #<$5f3f, #>$5f3f
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LDA #$00
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jsr memset
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LDA #%10000000; bit_1 = True
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ORA Screen_RAM_settings
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STA Screen_RAM_settings
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;; Paint the bitmap black. More bitmap: https://www.c64-wiki.com/wiki/53272, https://www.c64-wiki.com/wiki/Screen_RAM#Moving_of_screen_RAM
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Mov_16 B_start, B_start + 1, #<VIC_bank, #>VIC_bank
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Mov_16 B_end, B_end + 1, #<$5f3f, #>$5f3f
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LDA #$00
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jsr memset
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;;Sets the screen color to black and white
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Mov_16 B_start, B_start + 1, #<Screen_RAM, #>Screen_RAM
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Mov_16 B_end, B_end + 1, #<Screen_RAM_end, #>Screen_RAM_end
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LDA #%11110000
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jsr memset
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SEI ;Disable interups (not all)
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;;Disable BASIC ROM mohahaha
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LDA #%11111110
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AND $0001
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STA $0001
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;https://www.c64-wiki.com/wiki/Bank_Switching
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;Disable IO, CHAREN =0
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LDA #%11111011
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AND $0001
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STA $0001
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;; Sets the screen color to black and white
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Mov_16 B_start, B_start + 1, #<Screen_RAM, #>Screen_RAM
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Mov_16 B_end, B_end + 1, #<Screen_RAM_end, #>Screen_RAM_end
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LDA #%11110000
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jsr memset
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;; Disable maskeble interups (not all)
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SEI
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;; Disable BASIC ROM mohahaha
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LDA #%11111110
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AND $0001
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STA $0001
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; https://www.c64-wiki.com/wiki/Bank_Switching
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; Disable IO, CHAREN =0
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LDA #%11111011
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AND $0001
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STA $0001
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;;Disable non maskable interupts
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;;https://codebase64.org/doku.php?id=base:nmi_lock_without_kernal
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;; write to $FFFA/$FFFB possible (and needed) if BASIC ROM is disabled
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LDA #$00
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STA $CCCC
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LDA #<NMI_routine
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STA $FFFA
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LDA #>NMI_routine
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STA $FFFB
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LDA #$00 ;; stop Timer A
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STA $DD0E
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STA $DD04 ;; set Timer A to 0, after starting
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STA $DD05 ;; NMI will occur immediately
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LDA #$81
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STA $DD0D ;; set Timer A as source for NMI
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LDA #$01
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STA $DD0E ;; start Timer A -> NMI
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;; from here on NMI is disabled
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JMP NMI_routine_end
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NMI_routine:
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RTI ;; exit interrupt not acknowledged
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NMI_routine_end:
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.endscope
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