108 lines
1.6 KiB
ArmAsm
108 lines
1.6 KiB
ArmAsm
// #LAYOUT# STD * #TAKE
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// #LAYOUT# M65 * #TAKE
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// #LAYOUT# X16 BASIC_0 #TAKE
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// #LAYOUT# * * #IGNORE
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// See https://www.c64-wiki.com/wiki/Memory_(BASIC) for BASIC memory organization
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do_new:
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#if (ROM_LAYOUT_M65 && SEGMENT_BASIC_0)
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jsr map_BASIC_1
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jsr_ind VB1__do_new
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jmp map_NORMAL
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do_clr:
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jsr map_BASIC_1
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jsr_ind VB1__do_clr
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jmp map_NORMAL
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do_restore:
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jsr map_BASIC_1
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jsr_ind VB1__do_restore
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jmp map_NORMAL
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#else
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// See Computes Mapping the Commodore 64 - page 96
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ldy #$00
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tya
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sta (TXTTAB),y
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iny
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sta (TXTTAB),y
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// The book does not mention this, but IMHO it is necessary to initialize VARTAB here too
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clc
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lda TXTTAB+0
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adc #$02
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sta VARTAB+0
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lda TXTTAB+1
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adc #$00
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sta VARTAB+1
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do_clr:
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// See Computes Mapping the Commodore 64 - page 96
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// XXX check if original ROM does this too
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jsr JCLALL
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lda MEMSIZ+0
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sta FRETOP+0
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lda MEMSIZ+1
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sta FRETOP+1
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// The book is not precise here $31-$32 is definitely not the end of BASIC text
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lda VARTAB+0
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sta ARYTAB+0
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sta STREND+0
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lda VARTAB+1
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sta ARYTAB+1
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sta STREND+1
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// This is a good place to reset the temporary string stack
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jsr tmpstr_free_all_reset
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// FALLTROUGH (confirmed on real C64 that CLR indeed resets DATPTR)
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do_restore:
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// See Computes Mapping the Commodore 64 - page 98
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// Initial DATPTR value checked on real C64
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#if HAS_OPCODES_65CE02
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lda TXTTAB+0
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sta DATPTR+0
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lda TXTTAB+1
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sta DATPTR+1
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dew DATPTR
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#else
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sec
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lda TXTTAB+0
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sbc #$01
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sta DATPTR+0
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lda TXTTAB+1
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sbc #$00
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sta DATPTR+1
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#endif
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rts
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#endif // ROM layout
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