Added IO address decoding. Lorem ipsum demo (without sorting LCD cursor addressing problems).
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Daniele Verducci su MatissePenguin
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@ -1,13 +1,17 @@
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; HD44780 20x4 characters LCD display driver
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; @author Daniele Verducci
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; constants
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LCD_LINES_LEFT: DB 0x80, 0xA8, 0x94, 0xBC ;array defining lcd command codes for the first char of every line
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; variables
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;lcd_cur_x: EQU DRV_VAR_SPACE
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;lcd_cur_y: lcd_cur_x + 1
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lcd_cur_x: EQU DRV_VAR_SPACE
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lcd_cur_y: EQU lcd_cur_x + 1
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; functions
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lcd_init:
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; Inits the lcd display
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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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@ -26,27 +30,63 @@ lcd_init:
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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_print:
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Lcd_print:
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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_print
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; increment x position
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ld a, (lcd_cur_x)
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inc a
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ld (lcd_cur_x), a
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; if x position > 19, increment y position and set x to 0
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ld a, (lcd_cur_x)
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cp 20
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jp nz, Lcd_print ; if x position is not 20, continue cycle
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ld a, 0
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ld (lcd_cur_x), a ; else set x to 0
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; and increment y
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ld a, (lcd_cur_y)
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inc a
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ld (lcd_cur_y), a
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; if y > 3 set y to 0
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cp 4 ; a still contains lcd_cur_y: compare with 4
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jp nz, Lcd_print ; if y position is not 4, continue cycle
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ld a, 0
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ld (lcd_cur_x), a ; else set y pos to 0
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jp Lcd_print
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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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ld a, b
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ld (lcd_cur_x), a
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ld a, c
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ld (lcd_cur_y), a
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call lcd_locate
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ret
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; private
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; The cursor position can seem like black magic but it makes much more sense once you know that the HD44780 is designed to control a 40 character 4-line display. So if you have a 16×2 then you will only see the first 16 characters of the top two lines. Simple enough once you get used to taking these character positions into account. For example, in a 16×2 display, the first line is position 0-15. So 0x80 is the first position, 0x80 + 12 = 0x8C is the 13th (remember, they are zero indexed). The second line is a little tricky since it shows positions 64-79. Just add the position number (in decimal) to 0x80 (in hex) to get the hex address of the cursor position. The address is the command to move the cursor to that location. So, to move to the 13th position of the top line in a 16×2 Sparkfun Display, I would send “0xFE 0x8C”. The first byte warns the onboard microcontroller that a command is coming, and the second byte is the command.
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lcd_locate:
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ld a,0xFE
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out (LCD_INSTR_REG),a ; warns the lcd microcontroller that a command is coming
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ld a,0xA8
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out (LCD_INSTR_REG),a ; place cursor to first char of second line
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; warns the lcd microcontroller that a command is coming
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ld a, 0xFE
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out (LCD_INSTR_REG),a
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; get line start command code from array
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ld hl, LCD_LINES_LEFT ; load array pointer
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ld bc, lcd_cur_y ; load line number
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ld b, 0 ; since line number is only 8 bit, clean garbage on the upper bit
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add hl, bc ; sum first array element to line number to access correct array element. Now hl contains array pointer
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; now sum x offset to the start line code to obtain lcd controller complete position code
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ld a, (lcd_cur_x) ; load cursor x position
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add a, (hl) ; sum cursor x pos to line start code. Result is in a
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out (LCD_INSTR_REG),a ; send cursor position to lcd controller
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ret
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; Clears the screen
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lcd_cls:
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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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@ -1,21 +1,39 @@
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; Pat80 BIOS v0.01
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; @author: Daniele Verducci
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;
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; ROM is at 0x0000
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; RAM is at 0x8000
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; SYSTEM VAR SPACE: 0x8000 - 0x8FFF (4kb)
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; DRIVERS VAR SPACE: 0x9000 - 0x9FFF (4kb)
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; APPLICATION VAR SPACE: 0xA000 - 0xFFFF (24kb)
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; LCD is at I/O 0x00 and 0x01
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; MEMORY MAP
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; ROM is at 0x0000
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; RAM is at 0x8000
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; SYSTEM VAR SPACE: 0x8000 - 0x8FFF (4kb)
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; DRIVERS VAR SPACE: 0x9000 - 0x9FFF (4kb)
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; APPLICATION VAR SPACE: 0xA000 - 0xFFFF (24kb)
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; I/O MAP
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; I/O 0 (0x00 - 0x1F) LCD (uses 0x00 and 0x01)
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; I/O 1 (0x20 - 0x3F)
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; I/O 2 (0x40 - 0x5F)
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; I/O 3 (0x60 - 0x7F)
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; I/O 4 (0x80 - 0x9F)
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; I/O 5 (0xA0 - 0xBF)
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; I/O 6 (0xC0 - 0xDF)
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; I/O 7 (0xE0 - 0xFF)
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jp sysinit ; Startup vector: DO NOT MOVE! Must be the first instruction
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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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IO_0: EQU 0x00
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IO_1: EQU 0x20
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IO_2: EQU 0x40
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IO_3: EQU 0x60
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IO_4: EQU 0x80
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IO_5: EQU 0xA0
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IO_6: EQU 0xC0
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IO_7: EQU 0xE0
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LCD_INSTR_REG: EQU IO_0
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LCD_DATA_REG: EQU IO_0 + 1
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SYS_VAR_SPACE: EQU 0x8000
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DRV_VAR_SPACE: EQU 0x9000
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APP_VAR_SPACE: EQU 0xA000
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@ -23,9 +41,9 @@ APP_VAR_SPACE: EQU 0xA000
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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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DB "Pat80",0 ; null terminated string
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LIPSUM:
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DB "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",0
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DB "Lorem ipsum dolor siadipiscing elit. Sedt amet, consectetur dapibus nec nullam.",0
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@ -34,22 +52,44 @@ LIPSUM:
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include 'driver_hd44780.asm'
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; System initialization
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sysinit:
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call lcd_init
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Sysinit:
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call Lcd_init
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; position to line 2 char 3
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;ld b, 1
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;ld c, 1
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;call Lcd_locate
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; write characters to display
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ld bc, SYSINIT_GREETING
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call lcd_print ; write string to screen
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call lcd_locate
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;ld bc, SYSINIT_GREETING
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;call Lcd_print ; write string to screen
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ld bc, LIPSUM
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call lcd_print
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;call lcd_cls ; clear screen
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call Lcd_print
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;call count
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; IO TEST
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iotest:
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; do not test 0: is lcd
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ld a,0x00
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out (IO_1),a
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ld a,0x00
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out (IO_2),a
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ld a,0x00
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out (IO_3),a
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ld a,0x00
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out (IO_4),a
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ld a,0x00
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out (IO_5),a
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ld a,0x00
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out (IO_6),a
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ld a,0x00
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out (IO_7),a
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call Lcd_cls ; clear screen
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halt
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