.data

	.text
	; r0 .. param0
	; r1 .. param1
	; r2 .. param2
	; r15 .. stackpointer
	; r0 .. return

	; TODO: will the assembler be able to evaluate these expressions?
	UART_BASE=0x1000
	UART_STATUS=(UART_BASE+0x4)
	UART_RECV=(UART_BASE+0x8)
	UART_TRANS=(UART_BASE+0xC)
	UART_BAUD=(UART_BAUD+0x10)

	UART_TRANS_EMPTY=0
	UART_RECV_NEW=1

	TIMEOUT_START=0x13371337
	DEFAULT_PROG_START=0x200
	STACKSTART=0x500 ; FIXME
;-----
main:
	; setup stackframe
	ldil r15, STACKSTART@lo
	ldih r15, STACKSTART@hi

	ldil r3, TIMEOUT_START@lo
	ldih r3, TIMEOUT_START@hi

timeout_loop:
	ldil r3, UART_STATUS@lo
	ldih r3, UART_STATUS@hi
	ldw r3, 0(r3)
	andi r3, r3, 1 << UART_RECV_NEW
	jumpzs+ next; jump if zero

	branch recv_byte
	; we received the enter bootrom sign
	cmp r0, 0x48 ; 'H'
	jumpeq- bt_H

next:
	subi r3, r3, 1
	jumpnz+ timeout_loop

	; branch to default entry point
	ldil r0, DEFAULT_PROG_START@lo
	ldih r0, DEFAULT_PROG_START@hi
	jumpreg r0

;-----
send_byte:
	ldil r3, UART_STATUS@lo	
	ldih r3, UART_STATUS@hi
	ldw r3, 0(r3)
	andi r3, r3, 1 << UART_TRANS_EMPTY
	jumpzs+ send_byte ; jump if zero
	ldil r3, UART_TRANS@lo	
	ldih r3, UART_TRANS@hi
	stb r0, 0(r3)
	ret

;-----
send_word:
	; TODO: loop? (less codesize...)
	branch send_byte
	lrs r0, r0, 8
	branch send_byte
	lrs r0, r0, 8
	branch send_byte
	lrs r0, r0, 8
	branch send_byte
	ret

;-----
recv_byte:
	ldil r3, UART_STATUS@lo	
	ldih r3, UART_STATUS@hi
	ldw r3, 0(r3)
	andi r3, r3, 1 << UART_RECV_NEW
	jumpzs+ send_byte ; jump if zero
	ldil r3, UART_RECV@lo	
	ldih r3, UART_RECV@hi
	lwb r0, 0(r3)
	ret

;-----
recv_word:
	ldil r1, 0x0 
	branch recv_byte
	or r1, r1, r0

	branch recv_byte
	sll r0, r0, 8
	or r1, r1, r0

	branch recv_byte
	sll r0, r0, 16
	or r1, r1, r0

	branch recv_byte
	sll r0, r0, 24
	or r1, r1, r0

	addi r0, r1, 0x0
	ret


;-----
bootrom:
	branch recv_byte

	cmpi r0, 0x57 ; 'W'
	jumpeq- bt_W

	cmpi r0, 0x52 ; 'R'
	jumpeq- bt_R

	cmpi r0, 0x51 ; 'Q'
	jumpeq- bt_Q

	cmpi r0, 0x54 ; 'T'
	jumpeq- bt_T

	cmpi r0, 0x4a ; 'J'
	jumpeq- bt_J

	; cmpi r0, 0x48 ; 'H'
	; jumpeq bt_H
	; FALL THROUGH ;)

bt_H:
	ldisl r0, 0x4f ; 'O'
	branch send_byte
	jump bootrom

bt_W:
	branch recv_word ; receive addr
	addi r6, r0, 0x0
	branch recv_word ; receive instr
	stx r0, 0(r6)
	ldisl r0, 0x44 ; 'D'
	branch send_byte
	jump bootrom

bt_R:
	branch recv_word ; receive addr
	ldx r1, 0(r0)
	ldisl r0, 0x46 ; 'F'
	branch send_byte
	addi r0, r1, 0x0
	branch send_word
	jump bootrom

bt_Q:
	branch recv_word ; receive addr
	addi r6, r0, 0x0
	branch recv_word ; receive data
	stw r0, 0(r6)
	ldisl r0, 0x41 ; 'A'
	branch send_byte
	jump bootrom

bt_T:
	branch recv_word ; receive addr
	ldw r1, 0(r0)
	ldisl r0, 0x47 ; 'G'
	branch send_byte
	addi r0, r1, 0x0
	branch send_word
	jump bootrom

bt_J:
	branch recv_word
	jumpreg r0

; 101 instr. please update after modification