8 Keyboard Processing

This chapter describes the physical keyboards and keyboard-to-host interface supported by the VT510 video terminal.

8.1 Overview

The VT510 supports two keyboard layouts:

Any time the terminal is operating, a keyboard encoding is being used to translate graphic character keystrokes into character codes, called the keyboard character set. The Keyboard Character set is a function of the Keyboard Dialect, the default character set, the 7-bit or 8-bit characters setting, and any keyboard customization defined in terminal Set-Up.

When the graphic character assigned to a keystroke (which usually corresponds to the legend appearing on the keycap) has a corresponding character in the Keyboard Character set, the terminal transmits the corresponding character code for that keystroke. The code transmitted for any given keystroke can vary depending on the Keyboard Character set. If the graphic character assigned to a keystroke does not have a corresponding character in the Keyboard Character set, then that keystroke becomes dead.

The term keyboard layout describes the physical layout of a keyboard, specifically, the number of keys and their positions on the keyboard. The keys are marked with symbols which indicate their function. Graphic keys transmit codes that match the graphic character symbol on the key cap, whereas keys such as the Tab key transmit control codes. Modifier keys (Shift, Ctrl and Alt) change the behavior of other keys. Function keys transmit multi-byte sequences of control and character data; local function keys enable local terminal functions (For example, Set-Up, and Print Screen).

8.2 PC Keyboard—VT Style vs. PC Style

The VT510 is designed to operate with either a VT keyboard or an enhanced PC keyboard. These keyboards differ in the number and positioning of keys. This leads to different user expectations of where function and local function keys are positioned on the PC keyboard. For example, traditional VT keyboard users expect F2 and F3 to enable local functions for printing the screen and entering Set-Up. Traditional PC keyboard users expect that these same keys will send signals to the host to control the application. These keyboard layouts are called VT style and PC style layouts. The PC style layout is the factory default.

VT Style is an alternate way of mapping the PC keyboard to look like a VT keyboard. With this mapping, PC keys send the same function sequences as similarly named keys on the VT layout (Figure 8–1). Since the enhanced PC layout does not correspond key-for-key to the VT Layout, some adaptation is necessary. Some function keys, that are missing from the PC keyboard, can be created by pressing a Function Key in combination with Caps Lock (For example, press and hold Caps Lock while typing another key).

Pressing Caps Lock/Num Lock toggles between the VT Style and PC Style. When VT Style is selected, "VT" is displayed on the keyboard indicator line at the bottom of the screen. The style is saved in NVM when you select Save settings. VT Style and PC Style mappings apply to VT modes only.

Figure 8–1 VT Keyboard Layout
Figure 8–2 PC Keyboard Layout

(1) Main keypad, (2) Editing keypad, (3) Numeric keypad,
(4) Function keys, (5) Escape key, (6) Indicator lights.

8.2.1 Differences—PC Style vs. VT Style

The differences between PC Style and VT Style are:

8.3 Top Row Function Keys

There are 20 top row function keys on the VT layout and 12 on the enhanced PC layout. Caps Lock/F1 through Caps Lock/F10 keys on the enhanced PC layout transmit the same sequences as F11 through F20 in the VT layout. Additional unique function sequences are transmitted by pressing function keys in combination with Shift, Alt, or Ctrl keys. See DECFNK and DECPAK for details.

In VT Style, the F1 through F5 keys operate the same as on the VT layout. In VT Style, F13 (Print Screen), F14 (Scroll Lock), and F15 (Pause) send their corresponding function key sequences. In PC Style, the F1 through F5 keys send function sequences (unless re-programmed) while Print Screen, Scroll Lock, and Pause default to local functions.

8.4 Main Key Array

This section describes the main keys on the keyboard.

8.4.1 Character Sets

Only characters from the currently selected keyboard character set may be generated. All other graphic character keystrokes are ignored. The following keyboard character sets are supported: ISO Latin 1, ISO Latin 2, ISO Latin Cyrillic, ISO Latin Greek, ISO Latin Hebrew, ISO Latin 5 (Turkish), DEC Multinational, DEC Cyrillic, DEC Greek, DEC Hebrew and DEC Turkish. When 7-bit NRCS characters is selected, a corresponding 7-bit NRC set is supported based on the Keyboard Dialect.

PC character sets are not supported in VT modes since the terminal is being used as a conventional video terminal that happens to have a PC keyboard attached. New applications should be written to use ISO character sets. (PC character sets are available in PCTerm and SCO console mode.)

8.4.2 Caps Lock

The Lock function may operate in three ways:

Caps Lock Alphabetic keys send their shifted character.
Shift Lock All keys on the main key array send their shifted character.
Reverse Lock Pressing Shift temporarily reverses the effect of Caps Lock; that is, unshifted or lowercase alphabetic characters are transmitted.

Pressing and releasing the Caps Lock key toggles the lock state on or off.

The Caps Lock key is also used to generate keystrokes for keys that are not present on the keyboard. Known as keyboard extension, this is done by pressing and holding the Caps Lock key and then pressing the extension key. The lock state is not toggled when an extension keystroke is pressed. Extension keystrokes are shown in Table 8–5, Local Functions.

8.4.3 Tab Key

With an enhanced PC keyboard, pressing Shift/Tab causes a CBT sequence, CSI Z, to be transmitted. A horizontal tabulation code (HT, 0/9) is transmitted when a VT keyboard is used.

8.4.4 Left Alt

Left Alt on the PC layout corresponds to the Alt Function on the VT layout. Depressing the left Alt key performs the following functions (unless re-programmed):

8.4.5 Right Alt

The right Alt key appears on the North American, Hebrew, and Greek PC layouts. On other country layouts, the right Alt key appears as Alt Gr. Depressing the right Alt key performs the following functions (unless re-programmed):

8.4.6 Alt Gr

The right Alt key is marked as Alt Gr on some Enhanced PC layouts. The words Alt Gr are short for alternate graphic and corresponds roughly to the function of the compose key.

8.4.7 Modifier Keys

Table 8–1 shows the corresponding modifier keys for the VT and the enhanced PC layouts.

Table 8–1 VT Layout vs. Enhanced PC Layout Modifier Keys
VT Keyboard PC Keyboard
Left Shift Left Shift
Right Shift Right Shift
Lock Caps Lock
Ctrl Left Ctrl
none Right Ctrl
Left Compose Character Alt Gr
Right Compose Character none
Left Alt Left Alt
Right Alt none or Right Alt

There is no Ctrl key on the right side of the VT keyboard. Left and right Ctrl keys on the enhanced PC layout generates the single control function on the VT Layout.

There is no key labeled "compose" on the enhanced PC layout. Alt Gr (Right Alt) accesses the supplemental characters on the top right half of the keyboard on some enhanced PC layout keyboards. Alt Gr can be used with the numeric keypad to enter character codes directly. Left Alt/Space can be used to initiate compose sequences when VT Style is selected.

8.5 Editing Keypad Keys

Figure 8–3 shows the layout for the DEC VT and enhanced PC editing keypads.

Figure 8–3 Editing Keypad Legends on DEC and PC Layouts

When VT Style is selected, the enhanced PC layout editing keys transmit the same function sequences as the similarly legend editing keys in the VT layout. In PC Style, the Home key sends a Cursor Up (CUP) sequence to move the cursor home and the Delete key transmits a DEL (7/15).

Table 8–2 lists the key sequences for PC editing keypads.

Table 8–2 Editing Keypad Sequences for PC Layout
Enhanced PC Legend VT Legend VT Style Sequence PC Style Sequence
Insert Insert Here CSI 2 ~ CSI 2 ~
Delete Remove CSI 3 ~ DEL
Home Find CSI 1 ~ CSI H
End Select CSI 4 ~ CSI 4 ~
Page Up Prev Screen CSI 5 ~ CSI 5 ~
Page Down Next Screen CSI 6 ~ CSI 6 ~

In addition to these unshifted sequences, the editing keys can send unique sequences when pressed in combination with Shift, Alt, or Ctrl. See DECFNK for details.

8.6 Cursor Keypad Keys

The cursor keypad keys send the same sequences as the VT layout. Additional unique sequences can be sent when pressed in combination with Shift, Alt, or Ctrl. See DECFNK for details.

8.7 Numeric Keypad Keys

The enhanced PC layout numeric keypad has three differences from the VT layout:

  1. The four keys at the top of the keyboard are labeled Num Lock, /, *, and - instead of PF1 through PF4.
  2. The Num Lock key toggles the keypad keys, sending either numerals or function sequences.

In VT Style, with Application Mode enabled, the numeric keypad keys send the same sequences as the corresponding keys on a VT layout. When the numeric keypad is in numeric mode, the four keys at the top of the keyboard still operates as PF1 through PF4, and the + key sends an ASCII "+" character.

Table 8–3 shows the numeric keypad sequences in VT Style.

Table 8–3 PC Layout Numeric Keypad Sequences - VT Style
PC Key DEC Key Numeric Mode Application Mode
Num Lock PF1 SS3 P SS3 P
/ PF2 SS3 Q SS3 Q
* PF3 SS3 R SS3 R
- PF4 SS3 S SS3 S
Caps Lock/+ - SS3 m
+ , "+" SS3 l
. . "." SS3 n
Enter Enter CR SS3 M
0 0 "0" SS3 p
1 1 "1" SS3 q
2 2 "2" SS3 r
3 3 "3" SS3 s
4 4 "4" SS3 t
5 5 "5" SS3 u
6 6 "6" SS3 v
7 7 "7" SS3 w
8 8 "8" SS3 x
9 9 "9" SS3 y

In PC Style, when the numeric keypad is in Application Mode, the numeric keypad keys send the same sequences as the corresponding keys on the VT layout as shown in Table 8–3.

In PC Style, when the numeric keypad is in Numeric Mode, the keypad keys send either editing keypad sequences corresponding to the gray legend in the lower part of the keyboard, or the numerals corresponding to the black legend in the upper part of the keyboard. The numerals are sent when Shift or the Num Lock has been depressed. The Num Lock state can be toggled on or off by pressing the Num Lock key. "Num Lock" appears on the keyboard indicator line when this feature is activated. If Num Lock is on and "Reverse Lock" is activated, pressing Shift temporarily reverses the effect of Num Lock.

Table 8–4 lists the numeric keypad sequences in PC Style Numeric mode.

Table 8–4 PC Layout Numeric Keypad Sequences - PC Style, Numeric Mode
Keys Num Lock Off unshifted, or
Num Lock On with Shift
Num Lock On unshifted, or
Num Lock Off with Shift
Num Lock
/ / /
* * *
- - -
+ + +
.
Del
DEL .
Enter CR CR
0
Ins
CSI 2 ~ 0
1
End
CSI 4 ~ 1
2
v
CSI B 2
3
PgDn
CSI 6 ~ 3
4
<
CSI D 4
5 5
6
>
CSI C 6
7
Home
CSI H 7
8
^
CSI A 8
9
PgUp
CSI 5 ~ 9

8.8 Local Function Key Defaults

The keys used to perform local terminal functions differ between the VT keyboard, PC keyboard, and the mode selection. Table 8–5 shows the corresponding keys for the default local functions. The function number in Table 8–5 is used in the DECPFK host sequence or DECPAK's alternate function to specify a change to that local function key.

Table 8–5 Local Functions
Function Number Function VT Keyboard SCO Console PC Keyboard VT-Style PC Keyboard PC-Style PC Keyboard SCO

1 X means the function is not available in the default SCO state. If there is no "X" in the SCO Console column, then this means that the key sequence is the same as the VT Keyboard column. If there is no "X" in the PC Keyboard SCO column, then this means that the key sequence is the same as the PC Keyboard PC-Style column.

†The Shift2 Modifier is assigned to the Alt Shift key (German "right Compose") when it appears on the corresponding keyboard (German).

‡Toggle KB language is assigned to the named language key when it appears on the corresponding keyboard (Greek, Hebrew, and Russian).

± means the function switches alternately between on and off.

C&P means Copy and Paste.

Lock means the Lock key, Caps Lock key, or key with lock icon.

0 no function
1 Hold F1 Lock/F1 F1 Scroll Lock
2 Print F2 Lock/F2 F2 Print Screen
3 Set-Up F3 Lock/F3 F3 Lock/Print Screen
Lock/Sys Rq
or
Alt/Print Screen
5 Break F5 Lock/F5 F5 Lock/Pause
7 Hard Reset Ctrl/F3 Lock/Ctrl/F3 Ctrl/F3 Ctrl/Lock/Print Screen
8 Toggle Autoprint Ctrl/F2 Lock/Ctrl/F2 Ctrl/F2 Ctrl/Print Screen
9 Disconnect Shift/F5 Lock/Shift/F5 Shift/F5 Shift/Lock/Pause
10 Send Answerback Ctrl/F5 Lock/Ctrl/F5 Ctrl/F5 Ctrl/Lock/Pause
11 Print Composed Main Display Shift/F2 X1 Shift/F2 Shift/Print Screen X
20 Pan Up Ctrl/^ X Ctrl/^ Ctrl/^ X
21 Pan Down Ctrl/v X Ctrl/v Ctrl/v
24 Pan Prev Page Ctrl/Prev X Ctrl/Page Up Ctrl/Page Up
25 Pan Next Page Ctrl/Next X Ctrl/Page Down Ctrl/Page Down
30 Copy & Paste Mode F1 (hold down) Caps Lock/F1 F1 Scroll Lock
31 C&P Cursor Left < < <
32 C&P Cursor Down v v v
33 C&P Cursor Up ^ ^ ^
34 C&P Cursor Right > > >
35 C&P Start Selection Select Home Home
36 C&P Copy Remove End End
37 C&P Paste Insert Here Insert Insert
38 C&P ± Left-to-Right Select Home Home
41 Shift Modifier Left or right Shift Left or right Shift Left or right Shift
42 Control Modifier Ctrl Left or right Ctrl Left or right Ctrl
43 Alt Function Modifier Left or right Alt Left or right Alt Left or right Alt
44 Start Compose Left or right Compose Left Alt/Space
45* Group Shift Modifier Group Shift Alt/Gr Alt/Gr
46† Shift2 Modifier Alt/Shift
47 Primary KB language Ctrl/Alt/F1 Lock/Alt/Ctrl/F1 Ctrl/Alt/F1 Ctrl/Alt/F1 See SCO Console
48 Secondary KB language Ctrl/Alt/F2 Lock/Alt/Ctrl/F2 Ctrl/Alt/F2 Ctrl/Alt/F2 See SCO Console
49‡ ± KB language
51 ± Caps Lock State Lock Lock Lock
52 ± Num Lock State Num Lock Num Lock
53 ± VT/IBM Style X Lock
Num Lock
Lock
Num Lock
X
54 Extend Kbd Modifier Lock Lock
61 Screen saver
62 Calculator Lock/Alt/F12 Lock/Alt/F12 Lock/Alt/F12
63 Clock Lock/Alt/F11 Lock/Alt/F11 Lock/Alt/F11
64 Character table Lock/Alt/F10 Lock/Alt/F10 Lock/Alt/F10
65 Transfer result Shift/Enter Shift/Enter Shift/Enter
Note

See Chapter 2 to re-define keys using the Define Key Editor.

Table 8–6 lists the local functions for ASCII emulations.

Table 8–6 Local Functions for ASCII emulations
Function DEC VT Layout EPC Layout
Hold Screen F1 Scroll Lock
Print Page Ctrl/Shift/. kpd Ctrl/Shift/. kpd
Set-Up F3 Alt/Print Screen
Caps Lock/F3 Caps Lock/Print Screen
Break F5 Ctrl/Pause
Hard Reset Ctrl/F3 in Setup
Soft Reset Shift/F3 Alt/Shift/Print Screen
Autoprint Mode Ctrl/F2 Ctrl/Print Screen
Ctrl/Shift/F2 Ctrl/Shift/Print Screen
Alt/Ctrl/Shift/Print Screen
Disconnect Shift/F5 Pause
Send Answerback Ctrl/F5 Shift/Pause
Display Next Page Ctrl/Next Ctrl/Page Down
Shift/Ctrl/Next Ctrl/Shift/Page Down
Active Other Window Ctrl/Next or Ctrl/Prev Ctrl/Page Down or Ctrl/Shift/Page Down or Ctrl/Page Up or Ctrl/Shift/Page Up
Display Prev. Page Ctrl/Prev Ctrl/Page Up
Shift/Ctrl/Prev Ctrl/Shift/Page Up
Display Page 0 Ctrl/0 kpd Ctrl/0 kpd
Display Page 1 Ctrl/1 kpd Ctrl/1 kpd
Display Page 2 Ctrl/2 kpd Ctrl/2 kpd
Display Page 3 Ctrl/3 kpd Ctrl/3 kpd
Display Page 4 Ctrl/4 kpd Ctrl/4 kpd
Display Page 5 Ctrl/5 kpd Ctrl/5 kpd
Block Mode F4 Ctrl/Shift/Pause
Ctrl/F4
Shift/Ctrl/F5
Change Status Line Display Ctrl/> Ctrl/>
Ctrl/Shift/> Ctrl/Shift/>
Insert Mode Ctrl/PF4 Ctrl/Insert
Ctrl/Shift/PF4 Ctrl/Shift/Insert
Monitor Mode Ctrl/Shift/1 kpd Ctrl/Shift/1 kpd
Screen Saver Ctrl/Shift/PF3 Ctrl/Shift/End
Speed Scroll Rate Ctrl/Shift/^ Ctrl/Shift/^
Slow Scroll Rate Ctrl/Shift/v Ctrl/Shift/v
Home Cursor & Clear Display Ctrl/Shift/Home
Roll Active Window Up in Page Ctrl/^ Ctrl/^
Roll Active Window Down In Page Ctrl/v Ctrl/v
Toggle Split Screen Ctrl/Shift/- kpd Ctrl/Shift/- kpd
Raise Split Line Ctrl/- kpd Ctrl/- kpd
Lower Split Line Ctrl/, kpd N.A.
Adjust Window to Include Cursor Ctrl/Home
Cursor Drag Mode Ctrl/Shift/, kpd N.A.
Caps Lock State Lock Caps Lock
Num Lock State N.A. Num Lock
Keyclick State Shift/Enter kpd Shift/Enter kpd

8.8.1 Numeric Keypad Compose

Pressing and holding Compose, Alt or Alt Gr while typing a decimal number on the numeric keypad sends the corresponding decimal character code when the compose key is released. If the . key on the keyboard is pressed while entering a number, then the value entered before pressing the . key is multiplied by 16 and added to the value entered next. This supports column/row entry commonly used in character coding tables.

When accessibility aids are enabled, remember to Lock and Unlock the compose key when entering codes.

8.8.2 Accessibility Aids

Accessibility aids allow the user with limited motor skills to use modifier key combinations in a sequential manner rather than a simultaneous manner (default). All modifier key combinations are supported.

The Accessibility aids option is enabled by depressing the Shift key five times in succession. This option can be disabled by pressing and holding a modifier key while pressing another key.

Once enabled, this option provides two levels of assistance known as Latch and Lock. The Latch state is achieved by pressing a modifier key once and affects the next key pressed. The Lock state is achieved by pressing a modifier key twice. All keys pressed are affected by the modifier until they are unlocked by either depressing the modifier key again or depressing another modifier key twice. Once any modifier is in the Locked state, pressing other modifier keys adds those modifiers to the Locked state.

A small icon appears on the Keyboard Indicator Line or Status Line to provide user feedback on the changing modifier state.

The icons for each state are as follows:

Accessibility Aid Keys Enabled
Modifier Latched (Cleared on Next Keystroke)
Modifier Locked

When Accessibility aid keys are disabled, no icon is displayed on the Keyboard Indicator Line or Status Line.

8.9 Controlling Keyboard LEDs

The following sequences allow the host to control keyboard modifier states for Caps Lock, Scroll Lock, and Num Lock or keyboard LEDs to indicate program status. They are as follows:

ESC [ ? 108 h Set NumLock mode (DECNUMLK)
ESC [ ? 108 l Reset NumLock mode
ESC [ ? 109 h Set CapsLock mode (DECCAPSLK)
ESC [ ? 109 l Reset CapsLock mode

"Scroll Lock" or "Hold Screen" cannot be controlled from the host because it suspends transmission from the host and there is no way to release it.

DECLL controls keyboard LEDs independently of any keyboard state. The use of LEDs for this purpose conflicts with their use as keyboard state indicators. The host control selects a mode of how the keyboard LEDs are to be used: as keyboard indicators; or host indicators. If host indicators is selected, then the DECLL sequence can be used to control the keyboard LEDs.

The following control sequences are used to control keyboard LEDs.

ESC [ ? 110 h Set Keyboard LEDs Host Indicator Mode (DECKLHIM)
ESC [ ? 110 l Reset Keyboard LEDs Host Indicator Mode (default)
Note

See Chapter 2 to re-define keys using the Define Key Editor.

8.10 Keyboard Languages

Table 8–7 lists the keyboard languages available for the VT terminal.

Table 8–7 VT Keyboard Layouts
Austrian/German Greek Russian
Belgian/French Hebrew SCS
British Hungarian Slovak
Canadian-French/English Italian Spanish
Czech North American Swedish
Danish Norwegian Swiss-French
Dutch Polish Swiss-German
Finnish Portuguese Turkish F
Flemish Romanian Turkish Q

Table 8–8 lists the keyboard languages available for the PC terminal.

Table 8–8 Enhanced PC Keyboard Layouts
Belgian Greek Romanian
British Hebrew Russian
Czech Hungarian SCS
Danish Italian Slovak
Dutch Latin American Spanish
Finnish North American Swedish
French Norwegian Swiss-French
French-Canadian Polish Swiss-German
German Portuguese Turkish

8.11 Switching Between Keyboard Languages

The VT510 allows the user to easily switch between two different keyboard layouts for several languages (English and Hebrew, for example). This feature allows the VT510 to support both existing conventions and emerging standards for extending the graphic input repertoire and/or switching between languages in dual language environments.

The primary keyboard language corresponds to "Group 1" and generally references the legends on the left portion of the keyboard.

The secondary keyboard language corresponds to "Group 2" and generally references the legends on the right portion of the keyboard.

Unless otherwise overridden, Ctrl/Alt/F1 activates the primary keyboard language (locking shift), and Ctrl/Alt/F2 activates the secondary keyboard language. These factory defaults are standard on PCs.

Selecting a new Keyboard Dialect in Set-Up resets the keyboard group shift state to Group 1 and automatically initializes the keyboard character set and VT default character set as shown in table Table 8–9. The keyboard character set is initialized to match the VT default character set.

Table 8–9 Default Character Set when changing Keyboard Language
Keyboard Language VT Default Character Set If desired, change to ...
Austrian/German, Belgian/French, British, Canadian-English, Canadian-French, Flemish, Danish, Dutch, Finnish, Italian, Portuguese, North American, Norwegian, Spanish, Swedish, Swiss-French, Swiss-German. DEC MCS or ISO Latin-1 ISO Latin-1
Czech, Hungarian, Polish, Romanian, SCS, or Slovak ISO Latin-2 ISO Latin-1
Greek DEC Greek or ISO Latin-Greek ISO Latin-Greek
Hebrew DEC Hebrew or ISO Latin-Hebrew ISO Latin-Hebrew
Russian KOI-8 Cyrillic or ISO Latin-Cyrillic ISO Latin-Cyrillic
Turkish DEC Turkish or ISO Latin-Turkish ISO Latin-Turkish

If 7-bit NRCS characters is selected, then the following corresponding NRC sets are available on the VT keyboards:

VT keyboards:

The 7-bit NRCS character sets are not available on the following keyboards:

If 7-bit NRCS characters is selected, then the following corresponding NRC sets are available on the enhanced PC keyboards:

Enhanced PC Keyboards

The 7-bit NRCS character sets are not available on the following enhanced PC keyboards:

8.11.1 Non-Spacing Accent Marks

Accented characters that do not appear directly on a keyboard can often be entered by typing a non-spacing diacritical mark followed by a base character.

Table 8–10 Non-Spacing Accent Marks
Symbol Non-Spacing Accent Name
´ Acute accent
˘ Breve
ˇ Hacek (caron)
¸ Cedilla
^ Circumflex accent
¨ Diaeresis (umlaut)
˙ Dot above
˝ Double acute accent
` Grave accent
΄ Greek Tonos
¯ Macron
˛ Ogonek
° Ring above
~ Tilde

Keystrokes assigned non-spacing accent marks do not send any character code immediately, but are used instead to modify the code transmitted by the subsequent keystroke. If a keystroke that has been assigned a non-spacing accent mark is followed immediately by a graphic character, then this forms a valid character in the keyboard character set, and the corresponding character code is transmitted.

When a non-spacing diacritical key is pressed, "Compose" appears on the keyboard indicator line until the next subsequent keystroke.

If the keystroke immediately following the non-spacing diacritical keystroke does not form a valid character in the keyboard character set, then the non-spacing diacritical mark is converted to the corresponding character, if any, and transmitted from the current keyboard character set. The second keystroke is then processed normally. This "error recovery" is different from previous VT auto-compose processing; however, this process follows the emerging standard used on personal computers.

8.11.2 German

For German keyboards, the Group Shift (left Compose) key functions as the keyboard repertoire extension mechanism. Group 1 and Group 2 are defined within the German keyboard dialect and are used whenever the keyboard language is set to German. Group Shift operates as a single shift prefix if pressed and released or as a modifier key if pressed and held.

8.11.3 Hebrew

When Hebrew is selected as the Keyboard Dialect, the Ctrl/Hebrew key toggles between the primary and secondary keyboard language.

When switching into 7-bit Hebrew, lowercase English letters are swapped with their corresponding Hebrew characters throughout the display. The Shift/Hebrew key also performs this swapping function at any time.

8.12 Keystation Numbers

Figure 8–4 shows the keystation numbers for a VT keyboard.

Figure 8–4 VT Layout - Keystation Numbers

Figure 8–5 shows a typical legend for a North American VT keyboard.

Figure 8–5 VT Layout - Typical North American Key Legends
Figure 8–6 Enhanced PC Layout - Map Numbers
Figure 8–7 Enhanced PC Layout - Typical North American Key Legends

8.13 Scan Codes Sent in PCTerm Mode for EPC Keyboards

The following keys send the corresponding scan codes, regardless of any modifiers that may be in effect.

Key # Legend (U.S.) Scan Code
Make/Break¹

¹Make means when the key is pressed; Break means when the key is released.

²Not used on 101/102 keyboard layout.

†101 keyboard layout only

‡102 keyboard layout only

1 ` 29/A9
2 1 02/82
3 2 03/83
4 3 04/84
5 4 05/85
6 5 06/86
7 6 07/87
8 7 08/88
9 8 09/89
10 9 0A/8A
11 0 0B/8B
12 - 0C/8C
13 = 0D/8D
14 7D/FD²
15 Backspace 0E/8E
16 Tab 0F/8F
17 Q 10/90
18 W 11/91
19 E 12/92
20 R 13/93
21 T 14/94
22 Y 15/95
23 U 16/96
24 I 17/97
25 O 18/98
26 P 19/99
27 [ 1A/9A
28 ] 1B/9B
29 \ 2B/AB†
30 Caps Lock 3A/BA
31 A 1E/9E
32 S 1F/9F
33 D 20/A0
34 F 21/A1
35 G 22/A2
36 H 23/A3
37 J 24/A4
38 K 25/A5
39 L 26/A6
40 ; 27/A7
41 ' 28/A8
42 2B/AB‡
43 Return 1C/9C
44 Shift 2A/AA
45 56/D6‡
46 Z 2C/AC
47 X 2D/AD
48 C 2E/AE
49 V 2F/AF
50 B 30/B0
51 N 31/B1
52 M 32/B2
53 , 33/B3
54 . 34/B4
55 / 35/B5
56 73/F3²
57 Shift 36/B6
58 Left Ctrl 1D/9D
60 Left Alt 38/B8
61 Space 39/B9
62 Right Alt E0 38/E0 B8
64 Right Ctrl E0 1D/E0 9D
90 Num Lock 45/C5
91
7
Home
47/C7
92
4
<
4B/CB
93
1
End
4F/CF
94 7C/FC²
96
8
^
48/C8
97 Keypad 5 4C/CC
98
2
v
50/D0
99
0
Ins
52/D2
100 Keypad * 37/B7
101
9
PgUp
49/C9
102
6
>
4D/CD
103
3
PgDn
51/D1
104
.
Del
53/D3
105 Keypad - 4A/CA
106 Keypad + 4E/CE
107 7E/FE²
108 Enter E0 1C/E0 9C
109 78/F8²
110 Esc 01/81
112 F1 3B/BB
113 F2 3C/BC
114 F3 3D/BD
115 F4 3E/BE
116 F5 3F/BF
117 F6 40/C0
118 F7 41/C1
119 F8 42/C2
120 F9 43/C3
121 F10 44/C4
122 F11 57/D7
123 F12 58/D8
125 Scroll Lock 46/C6

The keys in the following table send different series of scan codes depending on the modifier state in effect (Shift, Control, Alt, and/or Num Lock). Many of them have a base scan code that is identical to another key. To make each key unique, some have an extra byte hex 'E0' or hex 'E1' added to their scan code sequence.

Key # Legend
(U.S.)
Base Case
Make/Break
Shift Case Make/Break Num Lock ON Make/Break

*When the left Shift key is pressed, the AA-2A shift break and make should envelope the base codes as shown in the previous table. When the right Shift key is pressed, the code B6 (right shift break) is sent in place of AA and the code 36 (right shift make) is sent in place of 2A. If both right and left Shift keys are pressed, then both B6 and AA are sent where AA is shown, and both 36 and 2A are sent where 2A is shown.

75 Ins E0 52/E0 D2 E0 AA E0 52/E0 D2 E0 2A* E0 2A E0 52/E0 D2 E0 AA
76 Del E0 53/E0 D3 E0 AA E0 53/E0 D3 E0 2A* E0 2A E0 53/E0 D3 E0 AA
79 < E0 4B/E0 CB E0 AA E0 4B/E0 CB E0 2A* E0 2A E0 4B/E0 CB E0 AA
80 Home E0 47/E0 C7 E0 AA E0 47/E0 C7 E0 2A* E0 2A E0 47/E0 C7 E0 AA
81 End E0 4F/E0 CF E0 AA E0 4F/E0 CF E0 2A* E0 2A E0 4F/E0 CF E0 AA
83 ^ E0 48/E0 C8 E0 AA E0 48/E0 C8 E0 2A* E0 2A E0 48/E0 C8 E0 AA
84 v E0 50/E0 D0 E0 AA E0 50/E0 D0 E0 2A* E0 2A E0 50/E0 D0 E0 AA
85 Pg Up E0 49/E0 C9 E0 AA E0 49/E0 C9 E0 2A* E0 2A E0 49/E0 C9 E0 AA
86 Pg Dn E0 51/E0 D1 E0 AA E0 51/E0 D1 E0 2A* E0 2A E0 51/E0 D1 E0 AA
89 > E0 4D/E0 CD E0 AA E0 4D/E0 CD E0 2A* E0 2A E0 4D/E0 CD E0 AA
Key # Legend (U.S.) Scan Code Make/Break Shift Case Make/Break
95 Keypad / E0 35/E0 B5 E0 AA E0 35/E0 B5 E0 2A*

The marker code Hex 'E0' precedes shift codes that are artificially produced by the keyboard logic. These artificially produced shift codes are not repeated during typamatic (auto repeat) operation of the corresponding key. Only the unique base code is repeated at the auto repeat rate. The terminal must ensure that both shift states are restored when all shift-dependent keys are released.

Key # Legend (U.S.) Scan Code Make/Break Ctrl Case and Shift
Case Make/Break
Alt Case Make/Break
124 PrtSc E0 2A E0 37/E0 B7 E0 AA E0 37/E0 B7
SysRq 54/D4

Notice there are two base scan codes associated with keystation 124. To ensure the make/break sequence, the code associated with the break must reflect the make code regardless of the Alt state at the time of the break.

Key # Legend (U.S.) Scan Code Make Ctrl down Make
126 Pause E1 1D 45 E1 9D C5
Break E0 46 E0 C6

The Pause/Break key is a make-only key, meaning it generates a code when pressed, not when released. All scan codes or actions associated with this key occur with the make of the key.

8.14 Scan Codes Sent in PCTerm Mode for VT Keyboards

All keystrokes send scan codes except:

Key Which sends . . .
Caps Lock F1 Hold
Caps Lock F2 Print
Caps Lock F3 Enter Set-Up
Caps Lock F5 Send Break

All keys including Shift, Alt, and Ctrl send make codes immediately upon being pressed, except the Caps Lock key. The make code for the Caps Lock key is sent after the Caps Lock key is released. The following keys send the corresponding scan codes, regardless of any modifiers that may be in effect.

Key # Legend (U.S.) Scan Code
Make/Break

¹On Numeric keypad.

²This is a make-only key; code is sent only when key is pressed.

42 \ 2B/AB
107 -¹ 7E/FE
124 F13 E0 3D/E0 BD
125 F14 E0 3E/E0 BE
126 Help E0 3F/E0 BF
127 Do 01/81 (Like Esc key on PC keyboard)
130 F17 E0 41/E0 C1
131 Print Screen E0 2A E0 37/E0 B7 E0 AA
Ctrl or Shift E0 37/E0 B7
Sys Rq Alt 54/D4
132 Scroll Lock 46/C6
133 Pause² E1 1D 45 E1 9D C5
Break² Ctrl E0 46 E0 C6