VT102 User Guide

4 Transmitted Characters

General

This chapter describes the characters generated by the VT102 keyboard. The keys are divided into three groups: standard keys, function keys, and numeric keypad keys.

Standard Keys

The keyboard generates American Standard Code for Information Interchange (ASCII) characters. The standard keys (Figure 4-1) generate lowercase ASCII characters when neither SHIFT or CAPS LOCK are down. These keys generate uppercase ASCII characters when either SHIFT or CAPS LOCK key are down. CAPS LOCK does not affect the nonalphabetic keys.

Figure 4-1 Standard Key Codes

Function Keys

The function keys (Figure 4-2) generate characters defined by the computer software or communication system. The following paragraphs describe the function keys.

Figure 4-2 Function Keys

BREAK/HERE IS

This key generates a break defined by the computer system when the break enable feature is on. This feature does not affect other key sequences using BREAK.

Hold down SHIFT and press BREAK to generate a long break disconnect. A long break disconnect usually disconnects the terminal from the communication line. See Break in Chapter 6 for more information about breaks and long break disconnects.

Hold down CTRL and press HERE IS to transmit the answerback message. See Chapter 3 for more information about the answerback feature.

Cursor Control Keys

In ANSI mode, with alternate (application) keypad mode selected, the cursor keys generate either application or cursor control sequences. Cursor key mode selects the type of sequence.

With numeric keypad mode selected, the cursor keys generate ANSI cursor commands. The computer selects both cursor key mode and keypad mode. See Cursor Key Character Selection in Chapter 5 for more information.

In VT52 mode, the cursor keys only generate VT52 cursor control sequences. Table 4-1 lists the ANSI and VT52 compatible cursor key characters.

Table 4-1 Cursor Control Key Codes
Cursor Key	ANSI Mode		VT52 Mode
Cursor Key	Cursor Key Mode Reset	Cursor Key Mode Set
↑	ESC [ A 033 133 101	ESC O A 033 117 101	ESC A 033 101
↓	ESC [ B 033 133 102	ESC O B 033 117 102	ESC B 033 102
→	ESC [ C 033 133 103	ESC O C 033 117 103	ESC C 033 103
←	ESC [ D 033 133 104	ESC O D 033 117 104	ESC D 033 104

Control Character Keys

Figure 4-3 shows the keys that generate control characters. You can generate control characters in two ways.

Hold down CTRL and press any unshaded key in Figure 4-3.
Press any shaded key in Figure 4-3 without using CTRL. These dedicated keys generate control characters without the use of CTRL.

Table 4-2 lists the control characters generated by the keyboard. Different computer systems may use each control character differently.

NOTE: The VT102 generates some control characters differently than previous DIGITAL terminals. Table 4-3 lists the changes.

Figure 4-3 Function Key Control Codes

Table 4-2 Control Codes Generated
Control Character	Mnemonic	Transmitted Code (Octal)	Key Pressed with CTRL	Dedicated Key
Null	NUL	000	Space Bar	-
Start of heading	SOH	001	A	-
Start of text	STX	002	B	-
End of text	ETX	003	C	-
End of transmission	EOT	004	D	-
Enquire	ENQ	005	E	-
Acknowledge	ACK	006	F	-
Bell	BEL	007	G	-
Back space	BS	010	H	BACK SPACE
Horizontal tabulation	HT	011	I	TAB
Linefeed	LF	012	J	LINE FEED
Vertical tabulation	VT	013	K	-
Form feed	FF	014	L	-
Carriage return	CR	015	M	RETURN*
Shift out	SO	016	N	-
Shift in	SI	017	O	-
Data link escape	DLE	020	P	-
Device control 1	DC1 (XON)	021	Q	-
Device control 2	DC2	022	R	-
Device control 3	DC3 (XOFF)	023	S	-
Device control 4	DC4	024	T	-
Negative acknowledge	NAK	025	U	-
Synchronous idle	SYN	026	V	-
End of transmission block	ETB	027	W	-
Cancel of previous word or character	CAN	030	X	-
End of medium	EM	031	Y	-
Substitute	SUB	032	Z	-
Escape	ESC	033	[	-
File separator	FS	034	\	-
Group separator	GS	035	]	-
Record separator	RS	036	~	-
Unit separator	US	037	?	-
Delete	DEL	177		DELETE
* The numeric keypad mode determines whether RETURN and ENTER generate the same control codes. The codes generated by RETURN are changed by two feature selections: The auto turnaround SET-UP feature when using half-duplex coded control (HDX B). The turnaround/disconnect SET-UP feature selected the turnaround character. If the turnaround character is carriage return (CR), the terminal transmits only one CR when you press RETURN. The line feed/new line feature. When this feature is on, RETURN generates two characters (CR, LF). When this feature is off, RETURN generates a CR.

Table 4-3 VT102 Key Changes
Control Code	VT102	Previous Terminals
NUL (octal 000)	CTRL Space Bar	CTRL @
RS (octal 036)	CTRL ~	CTRL ^
US (octal 037)	CTRL ?	CTRL _

Numeric Keypad Keys

These keys generate characters selected by the ANSI/VT52 feature and alternate (application) keypad mode. The computer selects application keypad mode. See Keypad Character Selection in Chapter 5 for more information.

In numeric keypad mode, the numeric keypad generates the numeric, comma, period, and minus sign characters used by the main keyboard. In application keypad mode, the numeric keypad generates control functions. Table 4-4 lists the characters generated by the numeric keypad.

Table 4-4 Keypad Codes
Key	ANSI Mode		VT52 Mode
Key	Numeric Keypad Mode	Application Keypad Mode	Numeric Keypad Mode	Application Keypad Mode
0	0 060	ESC O p 033 117 160	0 060	ESC ? p 033 077 160
1	1 061	ESC O q 033 117 161	1 061	ESC ? q 033 077 161
2	2 062	ESC O r 033 117 162	2 062	ESC ? r 033 077 162
3	3 063	ESC O s 033 117 163	3 063	ESC ? s 033 077 163
4	4 064	ESC O t 033 117 164	4 064	ESC ? t 033 077 164
5	5 065	ESC O u 033 117 165	5 065	ESC ? u 033 077 165
6	6 066	ESC O v 033 117 166	6 066	ESC ? v 033 077 166
7	7 067	ESC O w 033 117 167	7 067	ESC ? w 033 077 167
8	8 070	ESC O x 033 117 170	8 070	ESC ? x 033 077 170
9	9 071	ESC O y 033 117 171	9 071	ESC ? y 033 077 171
-	- (minus) 055	ESC O m 033 117 155	- (minus) 055	ESC ? m 033 077 155*
,	, (comma) 054	ESC O l 033 117 154	, (comma) 054	ESC ? l 033 077 154*
.	. (period) 056	ESC O n 033 117 156	. (period) 056	ESC ? n 033 077 156
ENTER†	CR or CR LF 015 or 015 012	ESC O M 033 117 115	CR or CR LF 015 or 015 012	ESC ? M 033 077 115
PF1	ESC O P 033 117 120	ESC O P 033 117 120	ESC P 033 120	ESC P 033 120
PF2	ESC O Q 033 117 121	ESC O Q 033 117 121	ESC Q 033 121	ESC Q 033 121
PF3	ESC O R 033 117 122	ESC O R 033 117 122	ESC R 033 122	ESC R 033 122
PF4	ESC O S 033 117 123	ESC O S 033 117 123	ESC S 033 123	ESC S 033 123
* These sequences are not generated by the VT52 terminal † In numeric keypad mode (application keypad mode off), you can change the ENTER character code with the linefeed/new line feature. When off, this feature causes ENTER to generate a single control character (CR, octal 015). When on, this feature causes ENTER to generate two characters (CR, octal 015 and LF, octal 012).