82 lines
1.6 KiB
NASM
82 lines
1.6 KiB
NASM
; Pat80 BIOS v0.01
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; @author: Daniele Verducci
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;
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; ROM is at 0x00
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; RAM is at 0x80
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; LCD is at I/O 0x00 and 0x01
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jp sysinit ; Startup vector: DO NOT MOVE! Must be the first instruction
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; SYSTEM CONFIGURATION
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LCD_INSTR_REG: EQU %00000000
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LCD_DATA_REG: EQU %00000001
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; CONSTANTS
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SYSINIT_GREETING:
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DB "Pat80 BIOS v0.1 ",0 ; null terminated string
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; System initialization
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sysinit:
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call lcd_init
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; write characters to display
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ld bc, SYSINIT_GREETING
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call lcd_write ; write string to screen
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call lcd_cls ; clear screen
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halt
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lcd_init:
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;reset procedure
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ld a,0x38
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out (LCD_INSTR_REG),a
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ld a,0x08
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out (LCD_INSTR_REG),a
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ld a,0x01
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out (LCD_INSTR_REG),a
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;init procedure
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ld a,0x38
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out (LCD_INSTR_REG),a
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ld a,0x0F
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out (LCD_INSTR_REG),a
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ret
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; Writes text starting from current cursor position
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; @param BC Pointer to a null-terminated string first character
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lcd_write:
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ld a, (bc) ; bc is the pointer to passed string's first char
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cp 0 ; compare A content with 0 (subtract 0 from value and set zero flag Z if result is 0)
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ret z ; if prev compare is true (Z flag set), string is finished, return
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out (LCD_DATA_REG),a ; output char
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inc bc ; increment bc to move to next char
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jp lcd_write
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; Set cursor position
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; @param B X-axis position (0 to 19)
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; @param C Y-axis position (0 to 3)
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lcd_locate:
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; TODO
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ret
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; Clears the screen
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lcd_cls:
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ld a,0x01
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out (LCD_INSTR_REG),a ; clear display
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ld a,0x02
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out (LCD_INSTR_REG),a ; cursor to home (top left)
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ret
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