diff options
Diffstat (limited to 'monitor.asm')
| -rw-r--r-- | monitor.asm | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/monitor.asm b/monitor.asm new file mode 100644 index 0000000..69d630e --- /dev/null +++ b/monitor.asm @@ -0,0 +1,243 @@ +;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; name: jaspos_monitor_dispstring
+;; @param string null terminated string to display
+;; @return none
+;; Print text onto the text screen
+;;
+jaspos_monitor_dispstring:
+ pop bp
+ pop ax
+ push bp
+ push di
+ push si
+ push es
+ push cx
+ push dx
+ mov si, ax
+ call jaspos_monitor_init
+.loop:
+ lodsb ; Load a byte from the string into AL
+ cmp al, 0 ; Compare the byte with null
+ jz .quit ; Return if it's a null
+ cmp al, 1 ; Check to see if it's a colour control char
+ jz .setcolour ; If so, jump to handle it
+ push ax ; Push the ASCII code of the character to print
+ call jaspos_monitor_dispchar ; Print the character to the screen
+ mov di, [VGAMemPointer] ; Load DI with the new, updated VGA memory pointer
+ jmp .loop ; Loop
+
+.setcolour:
+ lodsb ; Load the colour byte
+ mov [CharColour], al ; Set the CharColour to that byte
+ jmp .loop ; Go back to top of loop
+
+.quit:
+ mov [VGAMemPointer], di ; Move the updated cursor position into VGAMemPointer
+ call jaspos_monitor_updatecursor ; Update the cursor position on screen
+ pop dx
+ pop cx
+ pop es
+ pop si
+ pop di
+ ret ; Return to where this function was called
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; name: jaspos_monitor_dispchar
+;; @param char ASCII code of char to show
+;; @return none
+;; Print single character to the screen
+;;
+jaspos_monitor_dispchar:
+ pop bp
+ pop ax
+ push bp
+ push es
+ push di
+ call jaspos_monitor_init ; Set up the registers ready for printing text
+ cmp di, 4000d ; Is DI (our VGA memory pointer) at the end of the screen?
+ jge .scroll ; If so, scroll the screen up a line
+.checkchar:
+ cmp al, 8d ; Is the character a backspace?
+ jz .bs ; If so, jump to handle it
+ cmp al, 13d ; Is the byte a CR?
+ jz .cr ; if so, jump
+ cmp al, 10d ; Is the byte a LF?
+ jz .lf ; Jump if it is
+ stosb ; Store the byte in AL in memory. This happens if it's not a control char
+ mov al, [CharColour]
+ stosb
+.quit:
+ mov [VGAMemPointer], di
+ pop di
+ pop es
+ ret
+
+.bs:
+ sub di, 2
+ mov al, 32d
+ stosb
+ sub di, 2
+ mov al, [CharColour]
+ stosb
+ jmp .quit
+
+.cr:
+ add di, 160d ; Add 160 to the byte pointer, moving it down one line
+ jmp .quit ; Jump back to top of the loop
+
+.lf:
+ mov ax, di ; Move our current position/pointer into AX
+ xor dx, dx
+ mov di, 160d ; Load DI with 160 (# of bytes per line)
+ div di ; AX = AX / DI and DX = remainder
+ mul di ; AX = AX * DI
+ mov di, ax ; So now AX has been divided and had the remainder chopped off in doing so
+ xor ax, ax
+ jmp .quit ; and is now multiplied back, so the pointer is now at the start of current line
+
+.scroll:
+ push ds
+ push ax
+ push di
+ push si
+ mov cx, 0xB800 ; Load DS with the video segment
+ mov ds, cx ;
+ mov si, 160d ;
+ xor di, di ;
+ mov cx, 3840d ;
+ rep movsb ; Move the bytes
+
+ xor al, al ; We'll be storing nulls to clear the last line
+ mov cx, 160d
+ mov di, 3840d
+ rep stosb
+ pop si
+ pop di
+ sub di, 160d
+ pop ax
+ pop ds
+ jmp .checkchar
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; name: jaspos_monitor_init
+;; @param none
+;; @return none
+;; Puts right values into ES and DI for putting
+;; strings on the screen
+;;
+jaspos_monitor_init:
+ push ax
+ mov ax, 0xB800 ; Load AX with the VGA segment
+ mov es, ax ; and then ES
+ mov di, [VGAMemPointer] ; Load DI with VGA memory pointer
+ pop ax
+ ret
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; name: jaspos_monitor_clear
+;; @param none
+;; @return none
+;; Clears the text screen
+;;
+jaspos_monitor_clear:
+ push ax ; push our registers used
+ push cx
+ push di
+ push es
+ push 0x0000 ; Overly explicit XY co-ord
+ call jaspos_monitor_setcursorxy ; Set the cursor position
+ call jaspos_monitor_init
+ xor di, di ; Set our reading pointer to the base of the segment
+ mov cx, 2000d ; We'll be looping 2000 times
+.loop:
+ mov al, 0x20 ; Load AL with character to clear address with
+ stosb ; Store our byte
+ mov al, [CharColour] ;
+ stosb ;
+ loop .loop ; Loop
+ xor ax, ax ; Zero-out AX
+ mov [VGAMemPointer], ax ; Load nulled-out AX into pointer
+ pop es
+ pop di
+ pop cx
+ pop ax ; pop registers we used back off stack
+ ret
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; name: jaspos_monitor_setcursorxy
+;; @param coord word whose upper byte is the X lower byte is the Y coord
+;; @return none
+;; Set the XY position of the text cursor but NOT where the next
+;; byte will be printed to the screen
+;;
+jaspos_monitor_setcursorxy:
+ pop bp
+ pop ax
+ push bp
+ push cx
+ mov cx, ax
+ xor ah, ah
+ mov bx, 160d
+ mul bx
+ shr cx, 8
+ shl cl, 1
+ add ax, cx
+ mov [VGAMemPointer], ax
+ pop cx
+ ret
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; name: jaspos_monitor_getcursorxy
+;; @param none
+;; @return coord word whose upper byte is the X lower byte is the Y coord
+;; Gets the XY position of the text cursor.
+;;
+jaspos_monitor_getcursorxy:
+ push dx
+ mov ax, [VGAMemPointer] ; Load the current cursor position
+ mov dx, 160d ; Divide it by 160 (bytes per row)
+ div dl ;
+ shr ah, 1 ; Divide the X by 2
+ pop dx
+ ret
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; name: jaspos_monitor_updatecursor
+;; @param none
+;; @return none
+;; Moves where the current cursor's (the actual
+;; flashing underscore) position is. Updates the
+;; position according to the current VGA memory
+;; pointer.
+;;
+jaspos_monitor_updatecursor:
+ push ax
+ push bx
+ push dx
+ call jaspos_monitor_getcursorxy
+ mov dh, al
+ mov dl, ah
+ mov ax, 0x0200 ; AH = 2 - set cursor pos.
+ xor bh, bh ; clear BH
+ int 0x10 ; Int 10.02 - set cursor position
+ pop dx
+ pop bx
+ pop ax
+ ret
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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