diff --git a/debug.S b/debug.S
new file mode 100644
index 0000000..ab87983
--- /dev/null
+++ b/debug.S
@@ -0,0 +1,24 @@
+
+
+debug	mac
+	brl ]eom
+	dw $7771
+	str ']1'
+]eom
+	<<<
+
+*debuglab	mac
+*]1
+*	brl ]eom
+*	dw $7771
+*	str ']1'
+*]eom
+*	<<<
+
+*debugent mac
+*]1	ent
+*	brl ]eom
+*	dw $7771
+*	str ']1'
+*]eom
+*	<<<
diff --git a/vt100.key.S b/vt100.key.S
index 8ff35c4..198e468 100644
--- a/vt100.key.S
+++ b/vt100.key.S
@@ -6,6 +6,7 @@
 
 	mx %11
 	use vt.equ
+	use debug
 
 	ext dispatch
 
@@ -24,6 +25,7 @@ kmOption	equ %0100_0000
 kmCommand	equ %1000_0000
 
 keypress ent
+	debug keypress
 	lda KBD
 	bmi :key
 	rts
@@ -50,6 +52,7 @@ keypress ent
 
 	asl
 	tax
+	lsr ; restore
 	jmp (special,x)
 
 :ctrl
@@ -290,9 +293,9 @@ arrow
 	lda #ESC
 	jsr dispatch
 
-	tsb DECANM
-	bmi :vt52
-	tsb DECCKM
+	bit DECANM
+	bpl :vt52
+	bit DECCKM
 	bmi :cursor
 
 	lda #'['
diff --git a/vt100.link.S b/vt100.link.S
index a05f1df..6e9c2d7 100644
--- a/vt100.link.S
+++ b/vt100.link.S
@@ -2,7 +2,7 @@
 	ovr all
 * binary linker
 	lkv 0
-	org $6000
+	org $2000
 
 *	asm boot.S
 *	asm vt100.ctrl.S
@@ -33,4 +33,5 @@
 	lnk vt100.modem.L
 	lnk vt100.key.L
 
-	sav vt100.bin
+	typ $ff
+	sav vt100.sys
diff --git a/vt100.main.S b/vt100.main.S
index 373254b..a8d0f51 100644
--- a/vt100.main.S
+++ b/vt100.main.S
@@ -6,6 +6,7 @@
 
 	mx %11
 	use vt.equ
+	use debug
 
 	ext scroll_down
 	ext recalc_cursor,recalc_cursor_x,recalc_cursor_y
@@ -19,7 +20,7 @@ TXTSET		equ $c051
 VGCINT		equ $c023
 SCANINT		equ $c032
 
-main
+main	debug main
 
 	clc
 	xce
@@ -76,6 +77,11 @@ init
 
 	lda #23
 	sta DECBM
+	lda #$80
+	sta LOCAL
+
+	lda #st_vt52
+	sta state
 
 	jsr erase_screen
 	jsr init_modem
@@ -174,8 +180,8 @@ ctrl_1b ; escape -
 * vt100 - aborts current escape sequence and starts a new one.
 * vt52 - esc esc aborts and starts new 
 * vt50 - esc esc aborts
-	lda DECANM
-	bne :vt52
+	bit DECANM
+	bpl :vt52
 	lda #st_vt100_esc
 	sta state
 	rts
@@ -190,8 +196,8 @@ ctrl_1a
 * vt100 - abort current escape sequence
 * and display error character.
 * TODO - display error character (mouse text)
-	lda DECANM
-	bne :vt52
+	bit DECANM
+	bpl :vt52
 	lda #st_vt100
 	sta state
 	rts
diff --git a/vt100.modem.S b/vt100.modem.S
index 92e8e2d..385542b 100644
--- a/vt100.modem.S
+++ b/vt100.modem.S
@@ -16,7 +16,7 @@ SCCADATA	equ $c03b
 
 
 init_modem ent
-	sep #$30
+*	sep #$30
 * reset channel B (modem port)
 	ldx #9
 	lda #%01010001
diff --git a/vt100.screen.S b/vt100.screen.S
index 58552be..7201027 100644
--- a/vt100.screen.S
+++ b/vt100.screen.S
@@ -258,6 +258,7 @@ fill_screen ent
 * fill the entire screen with the a register.
 * text screen is out of order, so this doesn't use much code but
 * it's not linear either.
+* +64 bytes of screen hole data.
 	mx %11
 
 	sta >$000400
@@ -268,13 +269,13 @@ fill_screen ent
 
 	ldx #$0400
 	ldy #$0401
-	lda #40*24-2
-	mvn $01,$01
+	lda #40*24+64-2
+	mvn $010000,$010000
 
 	ldx #$0400
 	ldy #$0401
-	lda #40*24-2
-	mvn $00,$00
+	lda #40*24+64-2
+	mvn $000000,$000000
 
 * not needed since $0,$0 last
 *	phk
@@ -318,13 +319,13 @@ scroll_up ent
 	lda #40
 	ldx #]1
 	ldy #]2
-	mvn $1,$1
+	mvn $010000,$010000
 
 	lda #$40
 	lda #40
 	ldx #]1
 	ldy #]2
-	mvn $0,$0
+	mvn $000000,$000000
 
 	dec r0
 	bne *+5
@@ -412,13 +413,13 @@ scroll_down ent
 	lda #40
 	ldx #]1
 	ldy #]2
-	mvn $1,$1
+	mvn $010000,$010000
 
 	lda #$40
 	lda #40
 	ldx #]1
 	ldy #]2
-	mvn $0,$0
+	mvn $000000,$000000
 
 	dec r0
 	bne *+5
diff --git a/vt100.vt52.S b/vt100.vt52.S
index 8054224..2b1dc31 100644
--- a/vt100.vt52.S
+++ b/vt100.vt52.S
@@ -110,11 +110,11 @@ esc_A ; cursor up.
 
 esc_B ; cursor down
 	lda y
-	cmp #79
+	cmp #23
 	beq :rts
 	cmp DECBM
 	beq :rts
-	iny y
+	inc y
 	jmp recalc_cursor_y
 
 :rts	rts
@@ -225,6 +225,8 @@ vt52_dca ent
 	sta y
 :update
 	stz :tmp
+	lda #st_vt52
+	sta state
 	jmp recalc_cursor