.org $c000
sysinit:
	JSR viainit
	JSR videoinit
	JSR videodisplay

system:
	JMP kbinput1

viainit:

	LDA #$FF
	STA $B002	; set DDRB of 65C22#1 to all output
	LDA #$00
	STA $B003	; set DDRA of 65C22#1 to all input
	LDA #$00
	STA $B012	; set DDRB of 65C22#2 to all input	
	LDA #$00
	STA $B013	; set DDRA of 65C22#2 to all input

	RTS

videoinit:

	LDA #$00
	STA $B000	; set all control bits of MC6847 to low
	LDA #$00
	STA $9FFF	; set video address to zero
	RTS

videodisplay:

	LDA #$13
	STA $8000	; print T
	jsr videocount
	LDA #$04
	STA $8001	; print E
	jsr videocount
	LDA #$12
	STA $8002	; print S
	jsr videocount
	LDA #$13
	STA $8003	; print T
	jsr videocount
	RTS

videocount:
	LDX $9FFF	; load value of video counter to X
	INX		; increment video counter
	STX $9FFF 	; store X to video counter
	RTS

kbinput1:

	LDA $B02A

	CMP #$15	; compare keyboard input to scan code
	BEQ q
	CMP #$1D
	BEQ w
	CMP #$24
	BEQ e
	CMP #$2D
	BEQ r
	CMP #$2C
	JMP kbinput2

q:
	LDA #$10
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
w:
	LDA #$16
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
e:
	LDA #$04
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
r:
	LDA #$11
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS

kbinput2:
	
	CMP #$2C
	BEQ t
	CMP #$35
	BEQ y
	CMP #$3C
	BEQ u
	CMP #$43
	BEQ i
	JMP kbinput3

t:
	LDA #$13
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
y:
	LDA #$18
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS

u:
	LDA #$14
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
i:
	LDA #$08
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS

kbinput3:

	CMP #$44
	BEQ o
	CMP #$4D
	BEQ p
	CMP #$1C
	BEQ a
	CMP #$1B
	BEQ s
	JMP kbinput4

o:
	LDA #$0E
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
p:
	LDA #$0F
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
a:
	LDA #$00
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
s:
	LDA #$12
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
kbinput4:

	CMP #$23
	BEQ d
	CMP #$2B
	BEQ f
	CMP #$34
	BEQ g
	CMP #$33
	BEQ h
	JMP kbinput5

d:
	LDA #$03
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
f:
	LDA #$05
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
g:
	LDA #$06
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
h:
	LDA #$07
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS

kbinput5:
	
	CMP #$3B
	BEQ j
	CMP #$42
	BEQ k
	CMP #$4B
	BEQ l
	CMP #$1A
	BEQ z
	JMP kbinput6

j:
	LDA #$09
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
k:
	LDA #$0A
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
l:
	LDA #$0B
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
z:
	LDA #$19
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS

kbinput6:
	CMP #$22
	BEQ x
	CMP #$21
	BEQ c
	CMP #$2A
	BEQ v
	CMP #$32
	BEQ b
	JMP kbinput7

x:
	LDA #$17
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
c:
	LDA #$02
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
v:
	LDA #$15
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
b:
	LDA #$01	
	LDX $9FFF	
	STA $8000,X	
	jsr videocount
	RTS

kbinput7:

	CMP #$31
	BEQ n
	CMP #$3A
	BEQ m
	JMP system	

n:
	LDA #$0D
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS
m:
	LDA #$0C
	LDX $9FFF
	STA $8000,X
	jsr videocount
	RTS


	.org $fffc
	.word $c000