181 lines
3.2 KiB
NASM
181 lines
3.2 KiB
NASM
ink_black EQU 0
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ink_blue EQU 1
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ink_red EQU 2
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ink_magenta EQU 3
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ink_green EQU 4
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ink_cyan EQU 5
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ink_yellow EQU 6
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ink_white EQU 7
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black EQU ink_black
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blue EQU ink_blue
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red EQU ink_red
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magenta EQU ink_magenta
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green EQU ink_green
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cyan EQU ink_cyan
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yellow EQU ink_yellow
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white EQU ink_white
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paper_black EQU 0
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paper_blue EQU 8
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paper_red EQU 16
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paper_magenta EQU 24
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paper_green EQU 32
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paper_cyan EQU 40
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paper_yellow EQU 48
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paper_white EQU 56
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bright EQU 64
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flash EQU 128
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attr_list_end EQU flash | bright | ink_black | paper_black
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MODULE print
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bm_start EQU #4000
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attr_area EQU #5800
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bm_len EQU 6144
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attr_len EQU 768
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CHARS EQU #5c36
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char_posn:
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dw #4000
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MODULE print_string
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; Set HL to be row and column and follow the call with a null-terminated string
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; All registers preserved
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; char_posn will have been moved to after string, but HL will still have coordinates of string start
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@print_string:
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call set_char_posn
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ex (sp), hl
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push af
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loop:
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ld a, (hl)
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inc hl
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or a
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jr z, exit
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call print_char
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jr loop
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exit:
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pop af
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ex (sp), hl
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ret
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ENDMODULE
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MODULE print_char
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; Prints the single character from the A register
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; All registers preserved
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; char_posn will point to next square
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@print_char:
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push hl
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push de
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push af
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ld h, 0
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ld l, a
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add hl, hl
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add hl, hl
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add hl, hl
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ld d, h
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ld e, l
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ld hl, (print.CHARS)
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add hl, de
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ld d, h
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ld e, l
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ld hl, (print.char_posn)
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push bc
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ld b, 8
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loop:
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ld a, (de)
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ld (hl), a
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inc h
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inc de
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djnz loop
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ld hl, (print.char_posn)
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inc l
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jr nz, update_char_posn
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ld a, #50
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cp h
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jr nz, next_third
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ld hl, print.bm_start
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jr update_char_posn
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next_third:
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ld a, 8
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add a, h
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ld h, a
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update_char_posn:
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ld (print.char_posn), hl
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pop bc
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pop af
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pop de
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pop hl
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ret
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ENDMODULE
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MODULE set_char_posn
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; Pass row and column, in that order, in HL
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@set_char_posn:
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push hl
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push af
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ld a, h
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; check for top third
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ld h, %01000000
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sub 8
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jr c, set_column
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; check for middle third
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ld h, %01001000
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sub 8
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jr c, set_column
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; must be bottom third
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ld h, %01010000
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sub 8
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set_column:
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; restore the row offset of the third and shift it into upper 3 bits of L
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add a, 8
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sla a
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sla a
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sla a
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sla a
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sla a
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or l
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ld l, a
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ld (print.char_posn), hl
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pop af
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pop hl
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ret
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ENDMODULE
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MODULE set_attributes
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; Row and column in HL
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; db list of attributes follows call
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; terminate with attr_list_end byte (bright flashing black on black)
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@set_attributes:
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ex de, hl
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ex (sp), hl
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push de
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push hl
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ld h, 0
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ld l, d
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ld d, h
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add hl, hl
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add hl, hl
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add hl, hl
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add hl, hl
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add hl, hl
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add hl, de
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ld de, print.attr_area
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add hl, de
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pop de
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ex de, hl
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push af
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loop:
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ld a, (hl)
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inc hl
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cp attr_list_end
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jr z, exit
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ld (de), a
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inc de
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jr loop
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exit:
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pop af
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pop de
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ex (sp), hl
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ex de, hl
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ret
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ENDMODULE
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ENDMODULE
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