; Made by Alessandro Lo-Presti (Agilo) on Januari 28, 2008.
; A text engine I wrote as a proof-of-concept kind of deal.


.orgfill 0x1460             ; Start of General Purpose RAM.

; Just a note that I may be able to use later on in life:
;<Lupin^> uhm you cant inizialize ram
;<Lupin^> you'd have to read the values from the ROM and write the to RAM
;<Lupin^> the only way you can read the values that you put at 0x1460 (in the
;         ROM) is to read them from ROM using the memory wrap (never done that)

.orgfill 0x2100             ; Start of ROM space.
.db "MN"                    ; ROM ID (do not change or validation will fail).
.include "irq.asm"          ; Game cart IRQ vectors.


; Pokemon Mini game header.
.orgfill 0x219E             ; 0x219E - 0x21A3 must be empty.
.orgfill 0x21A4             ; Start of "NINTENDO" string.
.db "NINTENDO"              ; Magic signature checked by the BIOS.
.db "TXTE"                  ; Game code, 4 bytes.
.db "Text engine"           ; Name of ROM, 12 chars max.

.orgfill 0x21BC             ; Will contain the following string:
.db "2P"                    ; At this time it's unknown what "2P" stands for.

.orgfill 0x21D0             ; End of rom header, start of program code.
.include "irqhandlers.asm"  ; Game cart IRQ routine handlers.


; Code entry point.
start:
 movw	sp, 0x2000 ; Set SP to end of general purpose RAM (stack grows down).
 movw	nn, 0x2000 ; NN register points to hardware registers.

 ; Enable primary interrupts on all keys.
 movb	[nn+0x21], 0x0C

 ; Enable secondary interrupt for the power button (CPU will jump to 0x215C).
 movb	[nn+0x25], (1<<7)

 ; Clear all flags.
 movb	flags, 0


 ; Enable LCD: 12x16, Global rendering, BG rendering, Non-inverted.
 movb	[nn+0x80], 0b00001010
 ; Set refresh rate (60Hz / 2 = 30Hz).
 movb	[nn+0x81], 0b00001001

; Include the text engine.
.include "textengine.asm"

; Logics start here.
PM_loop:

 ; Write some text using the engine. :)
 writestr "Pokemon MiniText Engine Made by:    Agilo       www.agilo.nl"

 ; Move key status into a.
 movb	a, [nn+0x52]

 ; Invert background on A.
 test	a, 0x01
 jnz	_restore_screen
 orb	[nn+0x80], 0x01 ; Set the invert bit of the LCD controller.
 jmp	_no_restore_screen
_restore_screen:
 andb	[nn+0x80], 0xFE ; Clear the invert bit of the LCD controller.
_no_restore_screen:

 ; Wait for vblank.
 call	vblank

 jmp	PM_loop


; Wait a vblank.
vblank:
 mov	[nn+0x27], 0x80
_sloop:
 test	[nn+0x27], 0x80
 jz	_sloop
 ret


; Blocks are 8x8 pixels (8 bytes large).
.align 8

; Include the character map.
charmap:
.incbin charmap.bin