From 492a3bfbec93d598441816310ae61b683c07755e Mon Sep 17 00:00:00 2001
From: Kelvin Sherlock <ksherlock@gmail.com>
Date: Sat, 4 Sep 2021 17:52:35 -0400
Subject: [PATCH] adding everything in progress, regardless of state.

---
 screen.S     | 198 ++++++++++++++++++++++++
 table.py     |  73 +++++++++
 vt.equ.S     |  60 ++++++++
 vt100.S      | 177 ++++++++++++++++++++++
 vt100.csi.S  | 413 +++++++++++++++++++++++++++++++++++++++++++++++++++
 vt100.ctrl.S | 103 +++++++++++++
 vt100.esc.S  | 164 ++++++++++++++++++++
 vt100.link.S |  22 +++
 vt100.main.S | 147 ++++++++++++++++++
 vt100.tabs.S |  77 ++++++++++
 vt100.vt52.S | 228 ++++++++++++++++++++++++++++
 11 files changed, 1662 insertions(+)
 create mode 100644 screen.S
 create mode 100644 table.py
 create mode 100644 vt.equ.S
 create mode 100644 vt100.S
 create mode 100644 vt100.csi.S
 create mode 100644 vt100.ctrl.S
 create mode 100644 vt100.esc.S
 create mode 100644 vt100.link.S
 create mode 100644 vt100.main.S
 create mode 100644 vt100.tabs.S
 create mode 100644 vt100.vt52.S

diff --git a/screen.S b/screen.S
new file mode 100644
index 0000000..b9990cb
--- /dev/null
+++ b/screen.S
@@ -0,0 +1,198 @@
+
+	rel
+	mx %11
+
+	ent erase_line
+	ent erase_line_0
+	ent erase_line_1
+	ent erase_line_2
+
+erase_line
+; a = 0 - erase x - eol (inclusive)
+; a = 1 - erase 0 - x (inclusive)
+; a = 2 - erase 0 - eol
+	cmp #2
+	bcs :rts
+	asl
+	tax
+	jmp (:table,x)
+:rts rts
+
+:table
+	dw erase_line_0
+	dw erase_line_1
+	dw erase_line_2
+
+erase_line_2
+* erase entire line.
+	php
+	rep #$30
+	ldy #38
+	lda #"  "
+:loop
+	sta [text01],y
+	sta (text00),y
+	dey
+	dey
+	bpl :loop
+	plp
+	rts
+
+	mx %11
+
+erase_line_0
+* erase to eol
+
+	lda x
+	lsr
+	tay
+	lda #" "
+	bcs :half
+:loop
+	sta [text01],y
+:half	sta (text00),y
+	iny
+	cpy #40
+	bcc :loop
+	rts
+
+erase_line_1
+* erase to x (inclusive)
+
+	lda x
+	lsr
+	tay
+	lda #" "
+	bcc :half
+
+:loop
+	sta (text00),y
+:half	sta [text01],y
+	dey
+	bpl :loop
+	rts
+
+
+erase_screen	ent
+; a = 0 - erase [cursor, end] (inclusive)
+; a = 1 - erase [start, cursor] (inclusive)
+; a = 2 - erase [start, end]
+	cmp #2
+	bcs :rts
+	asl
+	tax
+	jmp (:table,x)
+:rts rts
+
+:table
+	dw erase_screen_0
+	dw erase_screen_1
+	dw erase_screen_2	
+
+erase_screen_2	ent
+* erase the entire screen.
+	php
+	rep #$30
+	lda #"  " ; high bit set.
+
+c00	cc $0400
+c01	cc $0480
+c02	cc $0500
+c03	cc $0580
+c04	cc $0600
+c05	cc $0680
+c06	cc $0700
+c07	cc $0780
+c08	cc $0428
+c09	cc $04a8
+c10	cc $0528
+c11	cc $05a8
+c12	cc $0628
+c13	cc $06a8
+c14	cc $0728
+c15	cc $07a8
+c16	cc $0450
+c17	cc $04d0
+c18	cc $0550
+c19	cc $05d0
+c20	cc $0650
+c21	cc $06d0
+c22	cc $0750
+c23	cc $07d0
+	plp
+	rts
+
+	mx %11
+
+erase_screen_0	ent
+* erase from cursor to the end.
+	mx %11
+	ldx #0 ; for jmp (,x)
+	lda x
+	ora y
+	beq :all
+
+	lda x
+	beq :x0
+	jsr erase_line_0
+	lda y
+	inc
+	bra :x1
+:x0
+	lda y
+:x1	cmp #23
+	bcs :rts
+	asl
+	tax
+:all	php ; clear_table will plp.
+	rep #$30
+	lda #"  "
+	jmp (clear_table,x)
+
+:rts	rts
+
+
+erase_screen_1	ent
+* erase from start to cursor.
+	jsr erase_line_1
+	lda y
+	bne :ok
+	rts
+:ok
+	php
+	rep #$30
+	lda y
+	dey
+	asl
+	tax
+	lda #"  "
+	jmp (:clear_table,x)
+:clear_table
+
+
+c23	cc $07d0
+c22	cc $0750
+c21	cc $06d0
+c20	cc $0650
+c19	cc $05d0
+c18	cc $0550
+c17	cc $04d0
+c16	cc $0450
+c15	cc $07a8
+c14	cc $0728
+c13	cc $06a8
+c12	cc $0628
+c11	cc $05a8
+c10	cc $0528
+c09	cc $04a8
+c08	cc $0428
+c07	cc $0780
+c06	cc $0700
+c05	cc $0680
+c04	cc $0600
+c03	cc $0580
+c02	cc $0500
+c01	cc $0480
+c00	cc $0400
+	plp
+	rts
\ No newline at end of file
diff --git a/table.py b/table.py
new file mode 100644
index 0000000..e11e9c3
--- /dev/null
+++ b/table.py
@@ -0,0 +1,73 @@
+
+
+import sys
+
+
+special = {
+}
+for x in range(0,0x20): special[chr(x)] = '^' + chr(0x40 + x)
+
+cmap = {
+	'\'': '\'',
+	'\"': '\"',
+	'?': '?',
+	'\\': '\\',
+	'a': '\a',
+	'b': '\b',
+	'f': '\f',
+	'n': '\n',
+	'r': '\r',
+	't': '\t',
+	'v': '\v',
+}
+
+
+
+argv = sys.argv[1:]
+
+chars = []
+for arg in argv:
+	# ^X is a control character
+	if len(arg) == 2 and arg[0] == '^':
+		c = chr(ord(arg[1]) & 0x1f)
+		chars.append(c)
+		continue
+	# \X is an escaped character
+	if len(arg) == 2 and arg[0] == '\\':
+		c = arg[1]
+		if c in cmap: chars.append(cmap[c])
+		continue
+
+	# X-Y is a range of characters.
+	if len(arg) == 4 and arg[1] == '-':
+		a = arg[0]
+		b = arg[2]
+		for c in range(ord(a),ord(b)+1):
+			chars.append(chr(c))
+		continue
+
+	chars.extend(arg)
+
+chars = list(set(chars))
+chars.sort()
+
+if not chars: exit(1)
+
+mmin = ord(chars[0])
+mmax = ord(chars[-1])
+
+print(":MIN\tequ {}".format(mmin))
+print(":MAX\tequ {}".format(mmax))
+print()
+
+
+
+
+print(":table")
+for x in range(mmin, mmax+1):
+	c = chr(x)
+	print("\tdw $0\t; {}".format(special.get(c, c)))
+
+# for c in chars:
+# 	x = ord(c)
+# 	print("\tdw $0\t; {}".format(special.get(c, c)))
diff --git a/vt.equ.S b/vt.equ.S
new file mode 100644
index 0000000..9d13b58
--- /dev/null
+++ b/vt.equ.S
@@ -0,0 +1,60 @@
+
+st_vt52		equ 0
+st_vt52_esc	equ 2
+st_vt52_dca	equ 4
+st_vt100	equ 6
+st_vt100_esc	equ 8
+st_vt100_csi	equ 10
+st_vt100_csi_2	equ 12
+st_vt100_esc_pound	equ 14 ; #
+st_vt100_esc_lparen	equ 16 ; (
+st_vt100_esc_rparen	equ 18 ; )
+
+st_vt100_esc_bad	equ 20
+st_vt100_csi_bad	equ 22
+
+ESC	equ $1b
+
+
+	dum 0
+state	ds 2
+x	ds 2
+y	ds 2
+DECTM	ds 2 ; top margin
+DECBM	ds 2 ; bottom margin
+
+LOCAL	ds 2 ; local mode
+DECANM	ds 2 ; ansi/vt52
+DECKPAM ds 2 ; alternate keypad
+DECCKM	ds 2 ; cursor key modes
+DECOM	ds 2 ; origin
+DECSCNM ds 2 ; screen mode
+DECAWM	ds 2 ; wrap
+DECARM	ds 2 ; auto repeat
+
+
+LNM	ds 2 ; new line
+SGR	ds 2 ; graphics, bit 1 = bold, 4 = underscore, 5 = blink, 7 = inverse
+
+* not supported
+
+*CHARSET	ds 2 ; 
+*GRAPHICS	ds 2 ; 
+
+*DECCOLM ds 2 ; character per line (80/132)
+*DECINLM ds 2 ; interlace
+*DECSCLM ds 2 ; scroll mode
+
+* DECDHL - double height line
+* DECDWL - double width line
+
+
+* parameters
+MAX_PCOUNT	equ 8
+pcount	ds	2
+parms	ds	MAX_PCOUNT
+pmod	ds	2
+
+r0	ds	2
+
+	dend
diff --git a/vt100.S b/vt100.S
new file mode 100644
index 0000000..0cfbf3a
--- /dev/null
+++ b/vt100.S
@@ -0,0 +1,177 @@
+
+
+
+vt100
+	mx %11
+	and #$7f
+	cmp #' '
+	bcs :notctrl
+	asl
+	tax
+	jmp (ctrl,x)
+:notctrl
+	ldx state
+	jmp (:state_table,x)
+
+
+
+:state_table
+	ext vt52_esc,vt52_dca
+	ext vt100_esc,vt100_csi,vt100_csi_2
+	ext vt100_esc_pound,vt100_esc_lparen,vt100_esc_rparen
+
+	dw char
+	dw vt52_esc
+	dw vt52_dca
+	dw char
+	dw vt100_esc
+	dw vt100_csi
+	dw vt100_csi_2
+	dw vt100_esc_pound
+	dw vt100_esc_lparen
+	dw vt100_esc_rparen
+
+
+
+
+
+vt100_csi_bad ent
+	cmp #'@'
+	blt :rts
+	ldx #st_vt100
+	stx state
+:rts	rts
+
+
+
+
+esc_csi
+	stz pcount
+	stz params
+	stz params+1
+	stz csi_private
+	lda #st_csi
+	sta state
+	rts
+
+
+csi
+	inc state
+	inc state
+	cmp #'?'
+	bne csi0
+	lda #$80
+	sta csi_private
+	rts
+
+csi0
+	cmp #';'
+	beq :semi
+	cmp #'0'
+	bcc csi_final
+	cmp #'9'+1
+	bcs csi_final
+:num
+	and #$0f ; 0-9
+	tay ; save
+	ldx pcount
+	lda params,x
+	asl ; x 2
+	sta params,x
+	asl ; x 4
+	asl ; x 8
+	clc
+	adc params,x
+	sta params,x
+	tya
+	clc
+	adc params,x
+	sta params,x
+	rts
+
+
+:semi
+	ldx pcount
+	inx
+	cpx #MAX_PCOUNT
+	bcs :srts
+	stx pcount
+	stz params,x
+
+:srts
+	rts
+
+
+csi_final
+* c, h, l have private modes.
+	bit csi_private
+	bmi :priv
+
+	cmp #:MIN_FINAL
+	bcc :rts
+	cmp #:MAX_FINAL+1
+	bcs :rts
+	asl
+	tax
+	jmp (:table,x)
+:rts	rts
+
+:priv
+	cmp #:MIN_FINAL_PRIV
+	bcc :rts
+	cmp #:MAX_FINAL_PRIV+1
+	bcs :rts
+	asl
+	tax
+	jmp (:table_priv,x)
+
+
+csi
+*
+* ESC [ encountered.
+*
+* ? -> DEC private
+* 0-9 -> parameter value
+* ; parameter delim
+* other - final character.
+
+	cmp #'0'
+	blt :notnum
+	cmp #'9'+1
+	bge :notnum
+
+	sep #$30
+	and #$0f
+	tay
+	ldx pcount
+	lda parms,x
+	asl
+	pha
+	asl
+	asl
+	clc
+	adc 1,s
+	sta 1,s
+	tya
+	adc 1,s
+	ply
+	sta parms,x
+	sep #$30
+]rts	rts
+:notnum
+	cmp #';'
+	bne :notsemi
+	ldx pcount
+	cpx #MAXPCOUNT
+	bge ]rts
+	inx
+	stx pcount
+	stz parms,
+	stz parms+1,x
+]rts	rts
+:notsemi
+	cmp #'?'
+	bne :final
+	sta ptype
+	rts
+:final
\ No newline at end of file
diff --git a/vt100.csi.S b/vt100.csi.S
new file mode 100644
index 0000000..3280282
--- /dev/null
+++ b/vt100.csi.S
@@ -0,0 +1,413 @@
+
+
+
+	rel
+	xc
+	xc
+
+	use vt.equ
+
+
+vt100_csi ent
+	inc state
+	inc state
+
+	stz pcount
+	stz parms
+	stz parms+1 ; some assume 2 parms.
+	stz pmod
+
+	tay ; save for modifier
+	cmp #:MIN
+	blt :bad
+	cmp #:MAX+1
+	bge :bad
+	sec
+	sbc #:MIN
+	asl
+	tax
+	jmp (:table,x)
+:bad
+	ldx #st_vt100
+	stx state
+:rts	rts
+
+:table
+
+* 0123456789;ycnlhgrqJKmABCDHf
+
+* based on testing - 
+* everything except '0' - '?' and control chars
+* will finish.
+* '?' only matters for h/l
+*  a misplaced ? (or anything in '0' - '?', except 0-9;)
+* will cancel the sequence AFTER it's finished.
+* < = > ? are allowed as an initial modifier but only '?' is private
+* a mis-placed < = > ? will prevent 0x20-0x2f from terminating the sequence.
+
+:MIN	equ 48
+:MAX	equ 121
+:table
+	dw :digit	; 0
+	dw :digit	; 1
+	dw :digit	; 2
+	dw :digit	; 3
+	dw :digit	; 4
+	dw :digit	; 5
+	dw :digit	; 6
+	dw :digit	; 7
+	dw :digit	; 8
+	dw :digit	; 9
+	dw digit	; :
+	dw semi
+	dw :rts	; <
+	dw :rts	; =
+	dw :rts	; >
+	dw :modifier	; ?
+	dw $0	; @
+	dw $0	; A
+	dw $0	; B
+	dw $0	; C
+	dw $0	; D
+	dw $0	; E
+	dw $0	; F
+	dw $0	; G
+	dw $0	; H
+	dw $0	; I
+	dw $0	; J
+	dw $0	; K
+	dw $0	; L
+	dw $0	; M
+	dw $0	; N
+	dw $0	; O
+	dw $0	; P
+	dw $0	; Q
+	dw $0	; R
+	dw $0	; S
+	dw $0	; T
+	dw $0	; U
+	dw $0	; V
+	dw $0	; W
+	dw $0	; X
+	dw $0	; Y
+	dw $0	; Z
+	dw $0	; [
+	dw $0	; \
+	dw $0	; ]
+	dw $0	; ^
+	dw $0	; _
+	dw $0	; `
+	dw $0	; a
+	dw $0	; b
+	dw $0	; c
+	dw $0	; d
+	dw $0	; e
+	dw $0	; f
+	dw $0	; g
+	dw $0	; h
+	dw $0	; i
+	dw $0	; j
+	dw $0	; k
+	dw $0	; l
+	dw $0	; m
+	dw $0	; n
+	dw $0	; o
+	dw $0	; p
+	dw $0	; q
+	dw $0	; r
+	dw $0	; s
+	dw $0	; t
+	dw $0	; u
+	dw $0	; v
+	dw $0	; w
+	dw $0	; x
+	dw $0	; y
+
+
+:digit
+	lsr ; undo asl
+	sta parms
+	rts
+:modifier
+	ldx #$40 ; bit -> v
+	stx pmod
+	rts
+
+
+vt100_csi_2 ent
+
+	; if < '0' and invalid modifier, don't terminate.
+	bit pmod
+	bmi :badmod
+	cmp #'@'
+	blt :0
+	ldx #st_vt100
+	stx state
+
+:0	cmp #:MIN
+	blt :bad
+	cmp #:MAX+1
+	bge :bad
+	sec
+	sbc #:MIN
+	jmp (:table,x)
+
+:badmod
+	cmp #'@'
+	blt :rts
+
+:bad
+	ldx #st_vt100
+	stx state
+:rts	rts
+
+:MIN	equ 48
+:MAX	equ 121
+:table
+	dw digit	; 0
+	dw digit	; 1
+	dw digit	; 2
+	dw digit	; 3
+	dw digit	; 4
+	dw digit	; 5
+	dw digit	; 6
+	dw digit	; 7
+	dw digit	; 8
+	dw digit	; 9
+	dw digit	; :
+	dw semi
+	dw :modifier	; <
+	dw :modifier	; =
+	dw :modifier	; >
+	dw :modifier	; ?
+
+:modifier
+	lda #$80
+	sta pmod
+	rts
+
+semi
+	ldx pcount
+	cpx #MAX_PCOUNT
+	bge :rts
+
+	inx
+	stx pcount
+	stz parms,x
+:rts	rts
+
+* parameter digit.  clamped to 255 (250+ rounds up to 255)
+* in 132 is the largest valid parameter so this is ok.
+digit
+	lsr ; undo asl
+	sta r0
+	ldx pcount
+	lda parms,x
+*	cmp #255
+*	beq :rts
+	cmp #25
+	bge :v
+
+	tay
+	lda :table,y
+*	clc ; cleared via cmp
+	adc r1
+	sta parms,x
+
+
+:rts
+	rts
+:v
+	lda #$255
+	sta parms,x
+	rts
+
+:table	da 0,10,20,30,40,50,60,70,80,90
+	da 100,110,120,130,140,150,160,170,180,190
+	da 200,210,220,230,240,250
+
+
+
+
+
+set_mode
+	; esc [ ... h (vt100)
+	; esc [ ? ... h (private)
+	ldy #$80
+	bra mode_common
+
+reset_mode
+	; esc [ ... l (vt100)
+	; esc [ ? ... l (private)
+	ldy #0
+
+mode_common
+	inc pcount
+	ldx #0
+:loop	lda parms,x
+	cmp #:MIN
+	blt :next
+	cmp #:MAX+1
+	bgt :next
+	phx
+	asl
+	tax
+	jsr (:table,x)
+	plx
+
+:next	inx
+	cpx pcount
+	blt :loop
+:rts	rts
+
+:MIN equ 0
+:MAX equ 20
+:table
+	dw :rts ; error
+	dw mode_DECCKM
+	dw mode_DECANM
+	dw :rts ; DECCOLM
+	dw :rts ; DECSCLM
+	dw mode_DECSCNM
+	dw mode_DECOM
+	dw mode_DECAWM
+	dw mode_DECARM
+	dw :rts ; DECINLM
+	dw :rts ; 10
+	dw :rts ; 11
+	dw :rts ; 12
+	dw :rts ; 13
+	dw :rts ; 14
+	dw :rts ; 15
+	dw :rts ; 16
+	dw :rts ; 17
+	dw :rts ; 18
+	dw :rts ; 19
+	dw mode_LNM
+*:mask	dw 0,$40,$40,$40,$40,$40,$40,$40,$40,$40
+*	dw 0,0,0,0,0,0,0,0,0,0,0
+
+
+mode_DECCKM
+	bit pmod
+	bvc :rts
+
+	sty DECCKM
+:rts	rts
+
+mode_DECANM
+	bit pmod
+	bvc :rts
+
+	sty DECANM
+	cpy #0
+	bne :rts
+* switch to vt52 mode
+	ldx #st_vt52
+	stx state
+:rts	rts
+
+
+*mode_DECCOLM
+*	sty DECCOLM
+*	rts
+
+
+mode_DECSCNM
+	bit pmod
+	bvc :rts
+
+* todo - invert on-screen characters?
+	sty DECSCNM
+:rts	rts
+
+mode_DECOM
+	bit pmod
+	bvc :rts
+
+	sty DECOM
+	; move to the new home position
+	stz x
+	stz y
+	cpy #0
+	beq :rts
+	lda #DECTM
+	sta y
+
+	phy
+	jsr update_cursor
+	ply
+
+:rts	rts
+
+mode_DECAWM
+	bit pmod
+	bvc :rts
+
+	sty DECAWM
+:rts	rts
+
+mode_DECARM
+	bit pmod
+	bvc :rts
+
+	sty DECARM
+:rts	rts
+
+mode_LNM
+	bit pmod
+	bvs :rts
+
+	sty LNM
+:rts	rts
+
+
+char_attr
+* esc [ ... m
+	inc pcount
+	ldx #0
+:loop	lda parms,x
+	cmp #8
+	bge :next
+	tay
+	lda SGR
+	and :and,y
+	ora :or,y
+	lda :table,y
+	sta SGR
+
+:next	inx
+	cpx pcount
+	blt :loop
+:rts	rts
+
+
+:and	db $00,$ff,$ff,$ff,$ff,$ff,$ff,$ff
+
+:or	db %0000_0000,%0000_0010,%0000_0000,%0000_0000
+	db %0001_0000,%0010_0000,%0000_0000,%1000_0000
+
+
+
+reset_tab
+* ESC H - set tab at current column [vt100.s]
+* ESC [ g, ESC [ 0 g - clear tab at column
+* ESC [ 3 g - clear all tabs
+
+	lda parm
+	beq :0
+	cmp #3
+	beq :3
+	rts
+:0
+	ldx x
+	stz tabs,x
+	rts
+:3
+	ldx #80-1
+:loop	stz tabs,x
+	dex
+	bpl :loop
+	rts
+
+	sav vt100.csi.L
diff --git a/vt100.ctrl.S b/vt100.ctrl.S
new file mode 100644
index 0000000..5a2a166
--- /dev/null
+++ b/vt100.ctrl.S
@@ -0,0 +1,103 @@
+
+
+*control chars
+	ext draw_char,update_cursor
+
+control	ent
+
+	asl
+	tax
+	jmp (:table,x)
+
+:table
+	dw :rts	; ^@
+	dw :rts	; ^A
+	dw :rts	; ^B
+	dw :rts	; ^C
+	dw :rts	; ^D
+	dw enq	; ^E
+	dw :rts	; ^F
+	dw bel	; ^G
+	dw bs	; ^H
+	dw tab	; ^I
+	dw lf	; ^J
+	dw vt	; ^K
+	dw ff	; ^L
+	dw cr	; ^M
+	dw so	; ^N
+	dw si	; ^O
+	dw :rts	; ^P
+	dw xon	; ^Q
+	dw :rts	; ^R
+	dw xoff	; ^S
+	dw :rts	; ^T
+	dw :rts	; ^U
+	dw :rts	; ^V
+	dw :rts	; ^W
+	dw can	; ^X
+	dw :rts	; ^Y
+	dw sub	; ^Z
+	dw esc	; ^[
+	dw :rts	; ^\
+	dw :rts	; ^]
+	dw :rts	; ^^
+	dw :rts	; ^_
+
+:rts	rts
+
+enq
+* send answer back message.
+* answer back message is a user-controllable string of text sent as-is
+* (with no specific terminator character)
+	rts
+bel
+* todo - trigger nice ensoniq beep.
+	rts
+
+
+bs
+* backspace, no wrap
+	lda x
+	beq :rts
+	dec x
+	jmp update_cursor
+:rts	rts
+
+tab
+* go to next tab stop
+	rts
+
+lf
+vt
+ff
+* vt and ff interpreted as lf
+* LNM: also do cr.
+	bit LNM
+	bpl :lnm
+	stz x
+:lnm
+	lda y
+	cmp BM ; bottom margin
+	bne :iny
+	jmp scroll_up
+:iny	inc y
+	jmp update_cursor
+
+cr
+	stz x
+	jmp update_cursor
+
+xon
+xoff
+* flow control...
+	rts
+can
+sub
+* cancel esc sequence and display error character
+	stz state
+	rts
+
+esc
+	lda #st_esc
+	sta state
+	rts
\ No newline at end of file
diff --git a/vt100.esc.S b/vt100.esc.S
new file mode 100644
index 0000000..415d719
--- /dev/null
+++ b/vt100.esc.S
@@ -0,0 +1,164 @@
+
+
+	rel
+	xc
+	xc
+
+	use vt.equ
+
+vt100_esc ent
+* #[()=>cH78DEM
+* based on testing, unspecified chars in the 0x20-0x2f range cause it to gobble
+* chars until 0x30- terminator (which ends the sequence but does not take an action)
+
+* esc 1 -> hangs? [undocumented]
+
+
+	ldx #st_vt100
+	stx state
+
+	cmp #:MIN
+	blt :bad
+	cmp #:MAX+1
+	bge :rts
+	sec
+	sbc #:MIN
+	asl
+	tax
+	jmp (:table,x)
+
+:bad
+	ldx #st_vt100_esc_bad
+	stx state
+:rts
+	rts
+
+:MIN	equ 35
+:MAX	equ 99
+
+:table
+	dw :pound	; #
+	dw :bad	; $
+	dw :bad	; %
+	dw :bad	; &
+	dw :bad	; '
+	dw :lparen	; (
+	dw :rparen	; )
+	dw :bad	; *
+	dw :bad	; +
+	dw :bad	; ,
+	dw :bad	; -
+	dw :bad	; .
+	dw :bad	; /
+	dw :rts	; 0
+	dw :rts	; 1
+	dw :rts	; 2
+	dw :rts	; 3
+	dw :rts	; 4
+	dw :rts	; 5
+	dw :rts	; 6
+	dw esc_7	; 7
+	dw esc_8	; 8
+	dw :rts	; 9
+	dw :rts	; :
+	dw :rts	; ;
+	dw :rts	; <
+	dw esc_eq	; =
+	dw esc_gt	; >
+	dw :rts	; ?
+	dw :rts	; @
+	dw :rts	; A
+	dw :rts	; B
+	dw :rts	; C
+	dw esc_D	; D
+	dw esc_E ; E
+	dw :rts	; F
+	dw :rts	; G
+	dw esc_H	; H
+	dw :rts	; I
+	dw :rts	; J
+	dw :rts	; K
+	dw :rts	; L
+	dw esc_M	; M
+	dw :rts	; N
+	dw :rts	; O
+	dw :rts	; P
+	dw :rts	; Q
+	dw :rts	; R
+	dw :rts	; S
+	dw :rts	; T
+	dw :rts	; U
+	dw :rts	; V
+	dw :rts	; W
+	dw :rts	; X
+	dw :rts	; Y
+	dw :rts	; Z
+	dw :rts	; [
+	dw :rts	; \
+	dw :rts	; ]
+	dw :rts	; ^
+	dw :rts	; _
+	dw :rts	; `
+	dw :rts	; a
+	dw :rts	; b
+	dw esc_c	; c
+
+
+
+:lparen
+	ldx #st_vt100_esc_lparen
+	stx state
+	rts
+
+:rparen
+	ldx #st_vt100_esc_rparen
+	stx state
+	rts
+
+:pound
+	ldx #st_vt100_esc_pound
+	stx state
+	rts
+
+
+esc_7 ; save cursor position, graphic rendition, and character set.
+	rts
+esc_8 ; restore cursor position, graphic rendition, and character set.
+	rts 
+
+esc_eq ; enter alternate keypad mode
+	lda #$80
+	sta DECKPAM
+	rts
+esc_gt ; exit alternate keypad mode
+	stz DECKPAM
+	rts
+
+esc_H ; set tab stop
+	ext set_tab
+	ldx x
+	jmp set_tab
+
+esc_E ; next line
+	stz x
+	; drop through
+esc_D ; index
+	rts
+
+esc_M ; reverse index
+	rts
+
+esc_c ; reset terminal.
+	rts
+
+
+vt100_esc_bad ent
+	cmp #'0'
+	blt :rts
+	ldx #st_vt100
+	stx state
+:rts
+	rts
+
+
+	sav vt100.esc.L
diff --git a/vt100.link.S b/vt100.link.S
new file mode 100644
index 0000000..6276036
--- /dev/null
+++ b/vt100.link.S
@@ -0,0 +1,22 @@
+
+	ovr all
+
+* binary linker
+	lkv 0
+	org $6000
+
+	asm boot.S
+	asm vt100.ctrl.S
+
+
+
+	lnk boot.S
+	pos ; reset
+
+
+	pos EMU_SIZE
+EMU_SIZE	ext 
+EMU_BLOCKS	geq EMU_SIZE+511\512
+
+
+	sav vt100.bin
\ No newline at end of file
diff --git a/vt100.main.S b/vt100.main.S
new file mode 100644
index 0000000..3a2123a
--- /dev/null
+++ b/vt100.main.S
@@ -0,0 +1,147 @@
+vt100
+	mx %11
+	and #$7f
+	cmp #' '
+	bcs :notctrl
+	asl
+	tax
+	jmp (:ctrl_table,x)
+:notctrl
+	ldx state
+	jmp (:state_table,x)
+
+
+
+:state_table
+	ext vt52_esc,vt52_dca_1,vt52_dca_2
+	ext vt100_esc,vt100_csi,vt100_csi_2
+	ext vt100_esc_pound,vt100_esc_lparen,vt100_esc_rparen
+
+	dw char
+	dw vt52_esc
+	dw vt52_dca_1
+	dw vt52_dca_2
+	dw char
+	dw vt100_esc
+	dw vt100_csi
+	dw vt100_csi_2
+	dw vt100_esc_pound
+	dw vt100_esc_lparen
+	dw vt100_esc_rparen
+
+
+:ctrl_table
+	dw ctrl_00,ctrl_01,ctrl_02,ctrl_03
+	dw ctrl_04,ctrl_05,ctrl_06,ctrl_07
+	dw ctrl_08,ctrl_09,ctrl_0a,ctrl_0b
+	dw ctrl_0c,ctrl_0d,ctrl_0e,ctrl_0f
+	dw ctrl_10,ctrl_11,ctrl_12,ctrl_13
+	dw ctrl_14,ctrl_15,ctrl_16,ctrl_17
+	dw ctrl_18,ctrl_19,ctrl_1a,ctrl_1b
+	dw ctrl_1c,ctrl_1d,ctrl_1e,ctrl_1f
+
+
+
+ctrl_00
+ctrl_01
+ctrl_02
+ctrl_03
+ctrl_04
+ctrl_05 ; answer ENQ
+ctrl_06
+ctrl_0e ; G1 character set
+ctrl_0f ; G0 character set
+ctrl_10
+ctrl_11 ; XON
+ctrl_12
+ctrl_13 ; XOFF
+ctrl_14
+ctrl_15
+ctrl_16
+ctrl_17
+ctrl_19
+ctrl_1c
+ctrl_1d
+ctrl_1e
+ctrl_1f
+	rts
+
+
+ctrl_07 ; ring the bell.
+	rts
+
+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
+	lda #st_vt100_esc
+	sta state
+	rts
+
+:vt52
+	lda #st_vt52_esc
+	sta state
+	rts
+
+ctrl_18
+ctrl_1a
+* vt100 - abort current escape sequence
+* and display error character.
+	lda DECANM
+	bne :vt52
+	lda #st_vt100
+	sta state
+	rts
+
+:vt52
+	lda #st_vt52
+	sta state
+	rts
+
+
+ctrl_09 ; tab
+* vt100 has adjustable tabs.
+	ext tab_table
+
+	ldx x
+lp:
+	cpx #79
+	bcs :rts
+	lda tab_table,x
+	bne :hit
+	inx
+	bra :lp
+
+	stx x
+
+	jmp update_cursor
+:rts	rts
+
+ctrl_0a ; line feed - cursor down w/ scroll
+ctrl_0b ; vertical tab
+ctrl_0c ; form feed.
+
+* if LNM is active, equivalent to CR, LF
+
+	lda #LNM
+	bne :lnm
+	stz x
+:lnm
+
+	lda y
+	cmp #23
+	blt :simple
+
+	lda #" "
+	sta cursor_saved_char
+	jmp scroll_down
+
+:simple
+	inc y
+	jmp update_cursor
+
+ctrl_0d ; carriage return - cursor to column 0.
+	stz x
+	jmp update_cursor
diff --git a/vt100.tabs.S b/vt100.tabs.S
new file mode 100644
index 0000000..5e21e12
--- /dev/null
+++ b/vt100.tabs.S
@@ -0,0 +1,77 @@
+
+
+	rel
+	xc
+	xc
+
+	use vt.equ
+
+
+init_tabs	ent
+
+
+	ldx #80
+:loop	stz tabs,x
+	dex
+	bpl :loop
+
+	lda #72
+	ldy #$80
+:tloop	tax
+	sty tabs,x
+	sec
+	sbc #8
+	bne :tloop
+
+	rts
+*:table	db 8*1,8*2,8*3,8*4,8*5,8*6,8*7,8*8*,8*9
+
+set_tab	ent
+* input x = x
+
+*	ldx x
+	cpx #80
+	bge :rts
+	lda #$80
+	sta tabs,x
+:rts	rts
+
+reset_tab ent
+* input x = x
+
+*	ldx x
+	cpx #80
+	bge :rts
+	stz tabs,x
+:rts	rts
+
+
+reset_all_tabs ent
+
+	ldx #80-1
+:loop	stz tabs,x
+	dex
+	bpl :loop
+	rts	
+
+next_tab_stop ent
+* input x = x
+
+*	ldx x
+	cpx 79
+	bge :80
+
+:loop	bit tabs,x
+	bmi :rts
+	inx
+	cpx #80
+	bcc :loop
+
+
+:80	ldx	#80
+:rts	rts
+
+
+tabs	ds 80
+
+	sav vt100.tabs.L
diff --git a/vt100.vt52.S b/vt100.vt52.S
new file mode 100644
index 0000000..1fd464e
--- /dev/null
+++ b/vt100.vt52.S
@@ -0,0 +1,228 @@
+*
+* vt52 emulation for the vt100
+*
+* ESC < exits 
+
+	lst off
+
+	rel
+	xc
+	xc
+
+	use vt.equ
+
+	ext update_cursor,write_modem,draw_char
+
+
+
+vt52_esc ent
+* ABCDFGHIJKYZ<>=
+
+
+	ldx #st_vt52
+	stx state
+
+	cmp #:MIN
+	blt :rts
+	cmp #:MAX+1
+	bge :rts
+	sec
+	sbc #:MIN
+	asl
+	tax
+	jmp (:table,x)
+
+:rts
+	rts
+
+
+:MIN	equ 60
+:MAX	equ 90
+:table
+	dw esc_lt	; <
+	dw esc_eq	; =
+	dw esc_gt	; >
+	dw :rts		; ?
+	dw :rts		; @
+	dw esc_A	; A
+	dw esc_B	; B
+	dw esc_C	; C
+	dw esc_D	; D
+	dw :rts		; E
+	dw esc_F	; F
+	dw esc_G	; G
+	dw esc_H	; H
+	dw esc_I	; I
+	dw esc_J	; J
+	dw esc_K	; K
+	dw :rts		; L
+	dw :rts		; M
+	dw :rts		; N
+	dw :rts		; O
+	dw :rts		; P
+	dw :rts		; Q
+	dw :rts		; R
+	dw :rts		; S
+	dw :rts		; T
+	dw :rts		; U
+	dw :rts		; V
+	dw :rts		; W
+	dw :rts		; X
+	dw esc_Y	; Y
+	dw esc_Z	; Z
+
+
+
+esc_lt
+* based on testing, this also resets graphics mode
+* (which we don't support anyhow.)
+	lda #$80
+	sta DECANM
+	lda #st_vt100
+	sta state
+	rts
+
+
+esc_eq ; enter alternate keypad mode
+	lda #$80
+	sta DECKPAM
+	rts
+
+esc_gt ; exit alternate keypad mode
+	stz DECKPAM
+	rts
+
+* cursor movement respects the scrolling region.
+esc_A ; cursor up.
+	lda y
+	beq :rts
+	cmp DECTM
+	beq :rts
+	dec y
+	jmp update_cursor
+
+:rts	rts
+
+
+esc_B ; cursor down
+	lda y
+	cmp #79
+	beq :rts
+	cmp DECBM
+	beq :rts
+	iny y
+	jmp update_cursor
+
+:rts	rts
+
+
+esc_C ; cursor right
+
+	lda x
+	cmp #79
+	bcs :rts
+	inc x
+	jmp update_cursor
+:rts	rts
+
+esc_D ; cursor left
+
+	lda x
+	beq :rts
+	dec x
+	jmp update_cursor
+:rts	rts
+
+esc_I ; cursor up w/ line scroll
+* based on testing, scrolling only occurs within the
+* scroll region.
+	rts
+esc_J rts
+esc_K rts
+
+
+esc_H ; cursor home
+	; based on testing, does not respect scrolling region but does
+	; respect origin mode.
+	stz x
+*	stz y
+*	bit DECOM
+*	bpl :go
+	lda DECTM
+	sta y
+
+:go	jmp update_cursor
+
+
+esc_F ; enter graphics mode
+*	lda #%0010
+*	tsb mode
+	rts
+esc_G ; exit graphics mode
+*	lda #%0010
+*	trb mode
+	rts
+
+esc_Y ; direct cursor address
+* vt100 - does not take effect until the end.
+* based on testing, there is internal state information,
+* so esc Y a esc B esc Y b is equivalent to esc Y a b
+*
+* if width exceeded, clamps at right margin.
+* if height exceeded, does not change.
+	lda #st_vt52_dca
+	sta state
+	rts
+
+esc_Z ; terminal identity.
+	; return ESC / Z
+	; based on testing, no display in local mode
+	bit LOCAL
+	bmi :local
+	lda #ESC
+	jsr write_modem
+	lda #'/'
+	jsr write_modem
+	lda #'Z'
+	jmp write_modem
+
+:local	rts
+*	lda #'Z'
+*	jmp draw_char
+
+
+
+vta52_dca ent
+* this differs from esc [ H in that invalid
+* values are ignored rather than clamped.
+* based on testing, does not respect DECOM.
+* based on testing, state is saved if ESC aborts, even
+* if switching to vt100 mode and back or ^X to cancel.
+
+	sec
+	sbc #' '
+
+	bit :tmp
+	bmi :go
+	ora #$80
+	sta :tmp
+	rts
+
+:go	; a = x
+	cmp #80
+	bge :y
+	sta x
+:y	lda :tmp
+	and #$7f
+	cmp #24
+	bge :update
+	sta y
+:update
+	stz :tmp
+	jmp update_cursor
+
+
+:tmp	ds 2
+
+
+	sav vt100.vt52.L