; *physical memory map*
;-----------------------
;-         ROM         -
;-        0.5 MB       -
;-   0x80000-0xFFFFF   -
;-----------------------
;-         RAM         -
;-        0.5 MB       -
;-   0x00000-0x7FFFF   -
;-----------------------

CPU	286
BITS 	16

TIMES 0x80000-($-$$) DB 0	;Fill bottom half of ROM with zeros.
					;Bottom half of address space used by RAM.
					;Controlled with A19 decode.

ORG 0x8000				;Usable ROM starts at physical address 0x80000

TOP:					;physically at 0x80000 in ROM
CLI					;disable interrupts
;MOV 	AX, code
;MOV 	DS, AX

;*** SETUP REGISTERS **********************************
MOV	AX,	0X0
;					;code segment
MOV	DS,	AX			;data segment
MOV	ES,	AX			;extra segment
MOV	SS,	AX			;stack segment
MOV	SP,	AX			;Start at 0, will wrap around to FFFE
;*** /SETUP REGISTERS *********************************



LOOP:
CALL ONE
CALL TWO
CALL THREE
CALL FOUR
JMP LOOP

ONE:
MOV 	AL, 	0x33			;00110011
OUT	0x02, AL
RET

TWO:
MOV 	AL, 	0xCC			;11001100
OUT	0x04, AL
RET

THREE:
MOV 	AL, 	0xAA			;10101010
OUT	0x02, AL
RET

FOUR:
MOV 	AL, 	0x55			;01010101
OUT	0x04, AL
RET


TIMES 0xFFFF0-($-$$) NOP	;Fill ROM with NOPs up to startup address
					;(upper portion of 1 MB addr space)
					;This will get to 0xFFFF0

RESET:				;at 0xFFFF0			Processor starts reading here
JMP 0x8000:0x0			;EA	00 00 00 80		Jump to TOP: label


TIMES 0x100000-($-$$) DB 1	;Fill the rest of ROM with bytes of 0x01