Installing and Using the VT320 Video Terminal

Appendix C

Contents

Glossary

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E VT320 Programming Summary

This appendix is a summary of the control functions and commands described in the VT320 Programmer Reference Manual. If you are a programmer, you can use this appendix as a quick-reference tool to program the VT320.

The appendix is divided into sections that correspond to the chapters of the programmer reference manual. For example, to find out more about 2 Character Encoding, you would go to Chapter 2 of the programmer reference manual.

2 Character Encoding

Character Sets and Codes

Computer systems store characters as a series of bits, usually 7 bits or 8 bits long. A bit is a binary digit. The VT320 can work with 7-bit or 8-bit systems. The VT320 provides the following character sets.

• ASCII
• DEC Supplemental Graphic
• ISO Latin-1 Supplemental Set
• DEC Special Graphic
• 12 national replacement character sets (NRCs)

An 8-bit system can use any of these character sets. A 7-bit system can use any set except the supplemental graphic sets.

Each character set has two types of characters, graphic characters and control characters. Graphic characters are the characters you can display on the screen. Control characters make the terminal perform a special function. See "Control Functions" in this appendix.

A code table is a convenient way of showing all the characters in a character set with their codes. Characters appear in rows and columns. One way of finding a character in a character set is by its column/row position. For example, in the ASCII character set the character H is at 4/8 (column 4, row 8).

Each character in a row uses the same binary code for its four least significant bits. This value appears at the left or right of each row. Each character in a column uses the same binary code for its three (or four) most significant bits. This value appears at the top of each column.

Next to each character appears the octal, decimal, and hexadecimal code for the character. Different programmers may prefer using octal, decimal, or hexadecimal values for different purposes.

DEC Multinational Character Set

National Replacement Character Sets (NRCs)

This table shows the characters in each NRC set that differ from the ASCII set.

ISO Latin Alphabet Nr 1 Supplemental Set

This is the right half of the ISO Latin-1 multinational character set. The left half is the ASCII character set.

DEC Special Graphic Character Set

ROW	COLUMN	0		1		2		3		4		5		6		7
	b8 BITS b7 b6 b5 b4 b3 b2 b1	0     0   0     0		0     0   0     1		0     0   1     0		0     0   1     1		0     1   0     0		0     1   0     1		0     1   1     0		0     1   1     1
0	0 0 0 0	NUL	0 0 0	DLE	20 16 10	SP	40 32 20	0	60 48 30	@	100 64 40	P	120 80 50		140 96 60	SCAN 3	160 112 70
1	0 0 0 1	SOH	1 1 1	DC1 (XON)	21 17 11	!	41 33 21	1	61 49 31	A	101 65 41	Q	121 81 51		141 97 61	SCAN 5	161 113 71
2	0 0 1 0	STX	2 2 2	DC2	22 18 12	"	42 34 22	2	62 50 32	B	102 66 42	R	122 82 52	HT	142 98 62	SCAN 7	162 114 72
3	0 0 1 1	ETX	3 3 3	DC3 (XOFF)	23 19 13	#	43 35 23	3	63 51 33	C	103 67 43	S	123 83 53	FF	143 99 63	SCAN 9	163 115 73
4	0 1 0 0	EOT	4 4 4	DC4	24 20 14	$	44 36 24	4	64 52 34	D	104 68 44	T	124 84 54	CR	144 100 64		164 116 74
5	0 1 0 1	ENQ	5 5 5	NAK	25 21 15	%	45 37 25	5	65 53 35	E	105 69 45	U	125 85 55	LF	145 101 65		165 117 75
6	0 1 1 0	ACK	6 6 6	SYN	26 22 16	&	46 38 26	6	66 54 36	F	106 70 46	V	126 86 56	°	146 102 66		166 118 76
7	0 1 1 1	BEL	7 7 7	ETB	27 23 17	'	47 39 27	7	67 55 37	G	107 71 47	W	127 87 57	±	147 103 67		167 119 77
8	1 0 0 0	BS	10 8 8	CAN	30 24 18	(	50 40 28	8	70 56 38	H	110 72 48	X	130 88 58	NL	150 104 68		170 120 78
9	1 0 0 1	HT	11 9 9	EM	31 25 19	)	51 41 29	9	71 57 39	I	111 73 49	Y	131 89 59	VT	151 105 69		171 121 79
10	1 0 1 0	LF	12 10 A	SUB	32 26 1A	*	52 42 2A	:	72 58 3A	J	112 74 4A	Z	132 90 5A		152 106 6A		172 122 7A
11	1 0 1 1	VT	13 11 B	ESC	33 27 1B	+	53 43 2B	;	73 59 3B	K	113 75 4B	[	133 91 5B		153 107 6B		173 123 7B
12	1 1 0 0	FF	14 12 C	FS	34 28 1C	,	54 44 2C	<	74 60 3C	L	114 76 4C	\	134 92 5C		154 108 6C		174 124 7C
13	1 1 0 1	CR	15 13 D	GS	35 29 1D	-	55 45 2D	=	75 61 3D	M	115 77 4D	]	135 93 5D		155 109 6D	£	175 125 7D
14	1 1 1 0	SO	16 14 E	RS	36 30 1E	.	56 46 2E	>	76 62 3E	N	116 78 4E	^	136 94 5E		156 110 6E	·	176 126 7E
15	1 1 1 1	SI	17 15 F	US	37 31 1F	/	57 47 2F	?	77 63 3F	O	117 79 4F	(blank)	137 95 5F	SCAN 1	157 111 6F	DEL	177 127 7F
		C0 CODES				GL CODES (DEC SPECIAL GRAPHICS)

Display Controls Font

You can have the terminal display the characters in your control functions, rather than performing the function. This is useful for debugging programs. To display control characters, you use the Controls feature in the Display Set-Up screen (Chapter 4).

Display Controls Font (Left Half)

ROW	COLUMN	0		1		2		3		4		5		6		7
	b8 BITS b7 b6 b5 b4 b3 b2 b1	0     0   0     0		0     0   0     1		0     0   1     0		0     0   1     1		0     1   0     0		0     1   0     1		0     1   1     0		0     1   1     1
0	0 0 0 0	NU	0 0 0	DL	20 16 10		40 32 20	0	60 48 30	@	100 64 40	P	120 80 50	`	140 96 60	p	160 112 70
1	0 0 0 1	SH	1 1 1	D1	21 17 11	!	41 33 21	1	61 49 31	A	101 65 41	Q	121 81 51	a	141 97 61	q	161 113 71
2	0 0 1 0	SX	2 2 2	D2	22 18 12	"	42 34 22	2	62 50 32	B	102 66 42	R	122 82 52	b	142 98 62	r	162 114 72
3	0 0 1 1	EX	3 3 3	D3	23 19 13	#	43 35 23	3	63 51 33	C	103 67 43	S	123 83 53	c	143 99 63	s	163 115 73
4	0 1 0 0	ET	4 4 4	D4	24 20 14	$	44 36 24	4	64 52 34	D	104 68 44	T	124 84 54	d	144 100 64	t	164 116 74
5	0 1 0 1	EQ	5 5 5	NK	25 21 15	%	45 37 25	5	65 53 35	E	105 69 45	U	125 85 55	e	145 101 65	u	165 117 75
6	0 1 1 0	AK	6 6 6	SY	26 22 16	&	46 38 26	6	66 54 36	F	106 70 46	V	126 86 56	f	146 102 66	v	166 118 76
7	0 1 1 1	BL	7 7 7	EB	27 23 17	'	47 39 27	7	67 55 37	G	107 71 47	W	127 87 57	g	147 103 67	w	167 119 77
8	1 0 0 0	BS	10 8 8	CN	30 24 18	(	50 40 28	8	70 56 38	H	110 72 48	X	130 88 58	h	150 104 68	x	170 120 78
9	1 0 0 1	HT	11 9 9	EM	31 25 19	)	51 41 29	9	71 57 39	I	111 73 49	Y	131 89 59	i	151 105 69	y	171 121 79
10	1 0 1 0	LF	12 10 A		32 26 1A	*	52 42 2A	:	72 58 3A	J	112 74 4A	Z	132 90 5A	j	152 106 6A	z	172 122 7A
11	1 0 1 1	VT	13 11 B	EC	33 27 1B	+	53 43 2B	;	73 59 3B	K	113 75 4B	[	133 91 5B	k	153 107 6B	{	173 123 7B
12	1 1 0 0	FF	14 12 C	FS	34 28 1C	,	54 44 2C	<	74 60 3C	L	114 76 4C	\	134 92 5C	l	154 108 6C	|	174 124 7C
13	1 1 0 1	CR	15 13 D	GS	35 29 1D	-	55 45 2D	=	75 61 3D	M	115 77 4D	]	135 93 5D	m	155 109 6D	}	175 125 7D
14	1 1 1 0	SO	16 14 E	RS	36 30 1E	.	56 46 2E	>	76 62 3E	N	116 78 4E	^	136 94 5E	n	156 110 6E	~	176 126 7E
15	1 1 1 1	SI	17 15 F	US	37 31 1F	/	57 47 2F	?	77 63 3F	O	117 79 4F	_	137 95 5F	o	157 111 6F	DT	177 127 7F
		C0 CODES				GL CODES (ASCII GRAPHICS)

Control Functions

Programmers use control functions to make the VT320 perform a range of special actions, from the simple (moving the cursor) to the complex (emulating another terminal). The way you enter control functions in an application depends on two factors: your computing system and the programming language you use.

There are two types of control functions, single-character and multiple-character. Single-character functions, called control characters, perform simpler functions. There are two groups of control characters, C0 and C1. C0 characters appear in columns 0 and 1 of the code tables. C1 characters appear in columns 8 and 9. C1 characters are not available in 7-bit systems. The next section lists the function of each control character.

Control functions can perform more complex functions. There are three types of multiple-character control functions: escape sequences, control sequences, and device control strings. Each type begins with a certain control character.

Escape Sequences

An escape sequence begins with the C0 character ESC, followed by one or more graphic characters from the ASCII set. The ESC character tells the system that the graphic characters are part of a control function, not characters to be displayed. For example,

ESC # 6

is an escape sequence that changes the current line of text to double-width characters. Escape sequences use only 7-bit characters, and can be used in 7-bit or 8-bit systems.

Control Sequences

A control sequence begins with the C1 character CSI, followed by one or more ASCII graphic characters. You can also express CSI as two 7-bit characters, ESC [. So you can express control sequences as escape sequences. For example, the following two sequences perform the same function -- they change the display from 80 to 132 columns per line.

CSI ? 3 h

ESC [ ? 3 h

Whenever possible use CSI instead of ESC [ to introduce a control sequence. You can only use CSI in 8-bit systems.

Device Control Strings

A device control string begins with the C1 character DCS, followed by one or more ASCII graphic characters, a data string, and the C1 character ST (string terminator). For an example of a device control string, see "Down-Line-Loading a Soft Character Set" in this appendix.

For 7-bit systems, you can express DCS as ESC P. You can express ST as ESC \.

C0 (7-Bit) Control Characters Recognized

Name	Mnemonic	Function
Null	NUL	Ignored.
Enquiry	ENQ	Sends the answerback message.
Bell	BEL	Sounds the bell tone if the bell is enabled in set-up.
Backspace	BS	Moves the cursor one character position to the left. If the cursor is at the left margin, no action occurs.
Horizontal tab	HT	Moves the cursor to the next tab stop. If there are no more tab stops, the cursor moves to the right margin. HT does not cause text to auto wrap.
Line feed	LF	Causes a line feed or a new line operation, depending on the setting of line feed/new line mode.
Vertical tab	VT	Treated as LF.
Form feed	FF	Treated as LF.
Carriage return	CR	Moves the cursor to the left margin on the current line.
Shift out (Locking shift 1)	SO (LS1)	Maps the G1 character set into GL. You designate G1 by using a select character set (SCS) sequence. See the VT320 Programmer Reference Manual, Chapter 5.
Shift in (Locking shift 0)	SI (LS0)	Maps the G0 character set into GL. You designate G0 by using a select character set (SCS) sequence. See the VT320 Programmer Reference Manual, Chapter 5.
Device control 1 (XON)	DC1	Also known as XON. If XON/XOFF flow control is enabled in set-up, DC1 clears DC3 (XOFF). This action causes the VT320 to continue sending characters.
Device control 3 (XOFF)	DC3	Also known as XOFF. If XON/XOFF flow control is enabled in set-up, DC3 causes the VT320 to stop sending characters. The terminal cannot resume sending characters until it receives a DC1 control character.
Cancel	CAN	Immediately cancels an escape sequence or control sequence in progress. The VT320 does not display any error characters.
Substitute	SUB	Immediately cancels an escape sequence or control sequence in progress. The VT320 displays a reverse question mark for an error character.
Escape	ESC	Introduces an escape sequence. ESC also cancels any escape sequence or control sequence in progress.
Delete	DEL	Ignored when received. DEL is not used as a fill character. Digital does not recommend using DEL as a fill character. Use NUL instead.

C1 (8-Bit) Control Characters Recognized

8-Bit Control Characters and Their 7-Bit Equivalents

3 Keyboard Codes

Codes Sent by Editing Keys

Codes Sent by Arrow Keys

Codes Sent by Numeric Keypad Keys

Codes Sent by the Top-Row Function Keys

Keys Used to Send 7-Bit Control Characters