VT100.net VT100 Technical Manual

Chapter 2 Operator Information

Part 1 Keyboard Controls and Indicators

The VT100 terminal normally performs a two-part function. It is an input device to a computer – information entered through the keyboard is sent to the computer. It is simultaneously an output device for the computer – that is, data coming in from the computer is displayed on the video screen. The following controls and indicators on the VT100 keyboard are illustrated in Figure 2-1.

Figure 2-1 VT100 Keyboard

SET-UP Key
Used in conjunction with other keys to perform specific functions such as setting tabs, scrolling, and altering terminal characteristics.

ON LINE Indicator
Lights to show that the VT100 is on-line and ready to transmit or receive messages.

LOCAL Indicator
Lights to show that the terminal is off-line and cannot communicate with the host device. In local mode the keyboard remains active and all characters typed are placed on the screen.

KBD LOCKED Indicator
Lights to show the keyboard has been turned off. The VT100 is still able to receive data from the host. This condition can be cleared by entering and exiting SET-UP mode.

L1-L4 Indicators
These indicators are turned on and off by the host. Consult your local operating procedures for the meaning of each indicator. L1-L4 also show self-test errors.

Keys
Each of these keys causes the VT100 to transmit a code that has a special meaning to your system. Consult your local operating procedures for the meaning of these keys. In SET-UP mode the ↑ and ↓ keys increase or decrease display brightness. The ← and → keys move the cursor left and right.

BACKSPACE Key
Transmits a backspace code.

BREAK Key
Transmits a break signal.

PF1-PF4 Keys
Each of these keys causes the VT100 to transmit a code that has a special meaning to your system. Consult your local operating procedures for the meanings of these keys.

Numeric Keypad
The numeric keypad enables numbers to be entered in calculator fashion. Each key in the numeric keypad generates the same character as the corresponding numeric key on the main keyboard. The ENTER key corresponds to the RETURN key. These keys may also be interpreted by the host computer as special function keys. Consult your local operating procedures for the meanings of these keys.

DELETE Key
Causes the VT100 to transmit a delete character code to the host system. The deleted character mayor may not be erased from the screen.

RETURN Key
Transmits either a carriage return (CR) code or a carriage return and line feed (LF) code. This is a SET-UP selectable feature.

LINEFEED Key
This key transmits a line feed code.

SHIFT Key
When pressed, this key enables the uppercase function of all keys. If a key does not have an uppercase function the SHIFT key is disregarded.

RESET Key
In SET-UP mode this key starts the reset sequence. This has the same result as turning the terminal power off and then on.

80/132 COLUMNS Key
In SET-UP A mode this key switches the display line size from 80 to 132 characters per line or from 132 to 80 characters per line.

RECEIVE SPEED Key
In SET-UP B mode this key steps the terminal through the receive baud rate settings in ascending order.

TRANSMIT SPEED Key
In SET-UP B mode this key steps the terminal through the transmit baud rate settings in ascending order.

TOGGLE 1/0 Key
In SET-UP B mode this key turns the selected operational feature on or off.

BELL Key
When pressed in combination with the CTRL key this key causes a bell code to be sent to the host.

SET-UP A/B Key
In SET-UP mode this key switches the terminal from SET-UP A to SET-UP B or from SET-UP B to SET-UP A.

LINE/LOCAL Key
In SET-UP mode this key switches the VT100 to communicate with your system (ON LINE) or stops the VT100 from communicating with your system (LOCAL).

CLEAR ALL TABS Key
In SET-UP A this key clears all horizontal tabs set in the VT100.

SET/CLEAR TAB Key
In SET-UP A this key sets or clears individual horizontal tabs.

CAPS LOCK Key
This key enables the transmission of uppercase alphabetic characters only. All numeric and special symbol keys remain in lowercase.

NO SCROLL Key
When first pressed, this key stops the transmission of data from the computer to the VT100. When pressed a second time, transmission resumes from where it was stopped. Check your local operating procedures to ensure that your system recognizes this key.

CTRL Key
When pressed in combination with another key, CTRL causes the VT100 to transmit a code that has a special meaning to your system.

TAB Key
This key transmits a tab code.

ESC Key
This key transmits a code that normally has a special meaning to your system. In many applications, it tells your system to treat the next keys pressed as a command.

Monitor Control
The VT100 monitor contains only one control, the power switch, shown in Figure 2-2.

Audible Indicators (Tones)
There are three audible indicators associated with the VT100: a short tone (click), a long tone (beep), and a series of long tones.

Short Tone (click)
The short tone sounds whenever a key is pressed, with the following exceptions:

Long Tone (beep)
The long tone sounds to indicate one of the following conditions:

Series of Long Tones
The terminal sounds the long tone several times in rapid succession to indicate that the nonvolatile memory (NVR) had difficulty reading or writing SET-UP features. (When this occurs, check the SET-UP features and then perform the recall or save operation again.)

Figure 2-2 VT100 Terminal (Rear View)

Part 2 SET-UP Mode

Unlike most terminals, the VT100 does not use switches or jumpers to individually turn the built-in terminal features on or off. Instead, the VT100 uses a nonvolatile memory (NVR) that always remembers what features have been selected, as if a swiitch had been set.

Selection and storage of built-in terminal features is performed in a special mode of operation called SET-UP mode. When you enter SET-UP mode, the status of features stored in temporary memory shows on the screen. You can then change the features and store any new feature selections either temporarily, by leaving SET-UP mode; or on a fixed basis, by performing a Save operation. In either case, terminal operation reflects the new feature selection. If a recall operation is performed, or the terminal is reset, or terminal power is turned off, all temporary feature settings are replaced by features that have been stored on a fixed basis.

SET-UP Features

SET-UP mode provides two brief summaries of the current feature status. The first presentation – SET-UP A - displays the location of tab stops set and a visual ruler that numbers each character position on the line. The second presentation – SET-UP B – summarizes the status of the other terminal features.

SET-UP A

To enter SET-UP A, press the SET-UP key. The display has a presentation similar to Figure 2-3. The bottom line of the display consists of a “ruler” that numbers each character position available on a line. Each tab stop is shown by a “T” above the ruler. If the tab stop(s) set are those desired, you may exit SET-UP mode by pressing the SET-UP key again or you may now change the tabs to meet your requirements.

Figure 2-3 SET-UP A Mode Presentation

SET-UP B

SET-UP B mode may only be entered from SET-UP A mode. To enter SET-UP B from SET-UP A press the 5 key on the main keyboard. The display looks like Figure 2-4. Figure 2-5 summarizes the SET-UP B presentation. This summary allows you to quickly determine what features are enabled. For additional information on a feature refer to in Part 3, SET-UP Feature Definitions.

To exit SET-UP B press the SET-UP key.

Figure 2-4 SET-UP B Mode Presentation

Determining What a SET-UP Feature Does

SET-UP features are basically a series of options in the VT100 that allow the terminal to be tailored to its operating environment. Table 2-1 lists each feature and shows one of the following general categories.

The installation category includes the initial installation of the terminal and any special options that may be attached to the terminal. If any options are added or removed, or the physical location of the terminal is changed, verify the settings of these SET-UP features.

Figure 2-5 SET-UP B Mode Summary
Table 2-1 Categories of SET-UP Features
Feature Installation Computer Compatibility Operator Comfort
Ansi/VT52 mode X
Answerback message X
Auto Repeat X
Auto XON/XOFF X
Bits per Character X
Characters per Line X
Cursor X
Interlace X
Keyclick X
Line/Local X
Margin Bell X
New Line X
Parity X
Parity Sense X
Power X
Receive Speed X
Screen Background X
Screen Brightness X
Scroll X X
Tabs X
Transmit Speed X
Wraparound X
(shifted) X

Computer compatibility contains the features that must be set correctly so that the VT100 can communicate with the host computer. An error in these settings may cause incorrect data to be sent to or received from the computer; or an error may prevent the VT100 from communicating with the computer. The settings for these features must be obtained from the host computer programmer, operator, or system manager since there are many combinations of settings designed to work with particular computers and special software. These feature settings normally change only when you need to communicate with a different computer or a unique software package.

The operator comfort category contains SET-UP features designed exclusively for the operator. These features allow the operator to tailor the VT100 to fit individual preference. These features do not affect any operations that occur between the terminal and the computer.

Part 3, SET-UP Feature Definitions, describes the specific function of each feature.

How to Change a SET-UP Feature

Changing any or all SET-UP features is a simple operation and is generally performed by following the same basic steps.

  1. Enter SET-UP mode by pressing the SET-UP key.
  2. Select the appropriate SET-UP mode by pressing the 5 key on the main keyboard each time you want to switch from SET-UP A to SET-UP B or from SET-UP B to SET-UP A.
  3. Position the cursor above the feature switch or tab stop to be changed. To position the cursor, the SPACE bar, ←, →, TAB, and RETURN keys may be used. Some features do not use this step since a specific key is dedicated to changing the feature.
  4. Change the feature setting by pressing either the 6 key on the main keyboard or the appropriate dedicated key. Each time the key is pressed the feature changes, generally to the opposite state.

Table 2-2 briefly summarizes SET-UP features, the SET-UP mode you must be in to change a feature, and the key used to change the feature setting.

Table 2-2 SET-UP Feature Change Summary
Feature Changed In SET-UP Mode Key to Change Feature
Answerback message B *
ANSI/VT52 mode B [6]
Auto Repeat B [6]
Auto XON/XOFF B [6]
Bits per Character B [6]
Brightness A ↑ ↓
Characters per Line A [9]
Cursor B [6]
Interlace B [6]
Keyclick B [6]
Line/Local A [4]
Margin Bell B [6]
New Line B [6]
Parity B [6]
Parity Sense B [6]
Power B [6]
Receive Speed B [6]
Screen B [6]
Scroll B [6]
Tabs A [2] and [3]
Transmit Speed B [7]
Wraparound B [6]
[3] (shifted) B [6]
* A special sequence is required for this feature. See the detailed features description.

Setting the Answerback Message

Setting the answerback message differs from setting any other terminal feature. An answerback message can be typed into the VT100, using the following steps.

  1. Place the terminal in SET-UP B mode.
  2. Press the SHIFT and A keys at the same time. The terminal responds by placing A = on the screen. (The SHIFT key is required. The CAPS LOCK key does not work here.)
  3. Type the message delimiter character which may be any character not used in the actual answerback message. The message delimiter character is not part of the answerback message. If a mistake is made when typing the answerback message, type the message delimiter character again and go back to step 2. This is the only way to correct errors in the answerback message.
  4. Type the answerback message. The message may be up to 20 characters, including space and control characters. Control characters are displayed as a character to indicate their presence in the message.
  5. Type the message delimiter character. Once the message delimiter character is typed the answerback message disappears from the screen.

Once the above steps have been completed the answerback message is temporarily stored in the VT100 and can be saved with the save operation.

Saving SET-UP Features

SET-UP features may be changed and stored on either a temporary or a fixed basis. To temporarily store a feature, exit SET-UP mode after changing the feature; the terminal now reacts according to the new setting. If a recall operation is performed, or the terminal is reset, or terminal power is turned off, all temporary feature settings are replaced by the features that have been stored on a fixed basis.

To store SET-UP feature settings on a fixed basis, perform a save operation. This is a simple operation that is accomplished by performing the following steps.

  1. Place the terminal in SET-UP mode.
  2. Press the SHIFT and S keys at the same time. The screen clears and the message “Wait” is displayed in the upper-left corner. After a brief wait, the terminal returns to SET-UP A mode.
NOTE
The save operation must be performed at the terminal keyboard. The computer cannot perform this operation, although it can temporarily modify the setting of VT100 features.

Once these steps have been performed, SET-UP features which had been temporarily stored are now stored on a fixed basis.

Recalling SET-UP Features

Temporarily stored SET-UP feature settings may differ from settings that are stored on a fixed basis. To return to the fixed settings, perform the recall operation as follows.

  1. Place the terminal in SET-UP mode.
  2. Press the SHIFT and R keys at the same time. The screen clears and the message “Wait” appears in the upper-left corner. After a brief wait the terminal returns to SET-UP A mode.
NOTE
When a recall operation is performed the contents of the screen are destroyed.

Resetting the Terminal

The VT100 may be reset from the keyboard. When the: terminal is reset, the terminal memory is cleared and the self-test program runs as if the terminal power switch was turned off and then back on. To reset the terminal:

  1. Place the terminal in SET-UP mode.
  2. Press the 0 key on the main keyboard. The VT100 is reset, the power on self-test runs, and the terminal reacts according to the fixed SET-UP features.
NOTE
When a reset operation is performed the contents of the screen are destroyed.

Part 3 Definitions SET-UP Feature

This section describes each SET-UP feature in detail (in alphabetical order) and states how each feature affects the terminal.

NOTE
Unmess otherwise stated, entering SET-UP mode and changing features does not result in the loss of data displayed on the screen.

ANSI/VT52 Mode

The VT100 terminal follows two programming standards – American National Standards Institute (ANSI) and VT52. In ANSI mode, the VT100 generates and responds to coded sequences per ANSI standards X3.41-1974 and X3.64-1977. In VT52 mode, the VT100 terminal is compatible with previous DIGITAL software using the VT52 video terminal. Both ANSI and VT52 modes are outlined in Appendix A of this manual.

Answerback Message

Answerback is a question and answer sequence where the host computer asks the terminal to identify itself. This feature allows the terminal to identify itself by sending a message to the host. The entire answerback sequence takes place automatically without affecting the screen or requiring operator action. The answerback message may also be transmitted by pressing the CTRL and BREAK Keys at the same time.

Auto Repeat

Auto repeat allows a key to be automatically repeated at the rate of about 30 characters per second when the key is held down for more than one-half second. The auto repeat feature affects all keyboard keys except the following:

Auto XON/XOFF

The VT100 can automatically generate synchronizing codes XON (DC1) and XOFF (DC3). XOFF stops data transmission from the computer to the terminal; XON resumes transmission. With the feature enabled, the VT100 generates the XOFF code when one of the following occurs:

  1. the internal buffer is nearly full
  2. the NO SCROLL key is pressed
  3. the terminal is placed in SET-UP mode
  4. CTRL-S is pressed.

When the buffer empties, the NO SCROLL key is pressed again, the terminal is taken out of SET-UP mode, or CTRL-Q is pressed, the VT100 transmits the XON code to resume transmission from computer to terminal.

If the host computer software does not support the XON/XOFF codes, data sent during buffer full conditions, or when the terminal is in SET-UP mode, may be lost.

NOTE
The VT100 always stops transmission when an XOFF (DC3) code is received and resumes transmission when an XON (DC1) code is received regardless of the Auto XON/XOFF feature setting.

Bits per Character

This feature allows the terminal to transmit and receive either 7- or 8-bit characters. When set for 8-bit operation, bit 8 is set to a space (or 0) for characters transmitted and is ignored for all characters received.

Characters per Line

The VT100 can display either 80 or 132 characters per line. In 80 character per line mode, the screen is 80 characters wide by 24 lines high. In 132 character per line mode, the screen is 132 characters wide by 14 lines high (24 lines if the VT100 is equipped with the Advanced Video Option). In 132 character per line mode, the displayed lines are physically the same width as 80 character per line mode but the characters are more compact.

NOTE
When changing from 80 to 132 character per line mode or vice versa, the current contents of the screen are lost.

Cursor

The VT100 has two cursor displays to indicate the “active positions” or where the next character will be placed on the screen. The cursor may be displayed as either a blinking underline (_) or a blinking block ([]). The cursor selection may perform an additional function; see the SGR escape sequence definition in Appendix A.

Interlace

This feature is used for high resolution options. The interlace feature should be turned off if such an option is not installed.

Keyclick Tone

The keyc1ick is a tone that sounds every time a key is pressed. The keyc1ick may be turned on or off to suit the operator’s needs. However, research and experience has shown that an operator is more accurate when there is audible feedback from the keyboard. Like the bell tone, the keyc1ick volume is not adjustable.

LINE/LOCAL

The LINE/LOCAL feature allows the operator to easily place the terminal in either an ON-LINE or a LOCAL (off-line) condition. When the terminal is on-line (ON-LINE indicator is lit) all characters typed on the keyboard are sent directly to the computer and messages from the computer are displayed on the screen. In the LOCAL condition (LOCAL indicator is lit), the terminal is electrically disconnected from the computer; messages are not sent to or received from the computer; and characters typed on the keyboard are echoed on the screen directly.

Margin Bell

The margin bell feature is much the same as the bell in a typewriter. If the cursor is eight characters from the end of the current line while typing, the VT100 sounds a tone to alert the operator.

New Line

The new line feature enables the RETURN key on the terminal to function like the return key on an electric typewriter. When the new line feature is enabled, pressing the RETURN key generates the carriage return (CR) and line feed (LF) codes. When a line feed code is received, the code is interpreted as a carriage return and line feed.

When the new line feature is disabled, the RETURN key generates only the CR code; an LF code causes the terminal to perform a line feed only.

NOTE
If double line feeds occur consistently, turn this feature off since the computer is already performing this function.

Parity

When enabled, parity checks for correct data transrnission. If a transmission error occurs, the VT100 detects it and indicates its presence by placing a checkerboard character ([]) on the screen in place of the character with the error. The parity sense feature determines if the parity is even or odd. When parity is disabled, no parity bit is transmitted or received.

Parity Sense

The parity sense feature defines which of the two methods of parity checking, odd or even, is being used by the VT100. If the parity feature is on, the terminal’s parity sense must be matched to the parity the computer is sending. If the parity sense features do not match, most characters sent to the computer are rejected even though the character was received correctly by the VT100. If a parity incompatibility occurs, the checkerboard character appears on the screen in place of the received character.

NOTE
If the parity feature is turned off, the parity sense selection is disregarded.

Power

During initial installation, the terminal display must be set to the power line frequency. In the U.S. this is 60 hertz.

Receive Speed

Receive speed must be set to match computer transmit speed. The VT100 is capable of receiving at any one of the following preselected speeds: 50, 75, 110, 134.5, 150, 200, 300, 600, 1200, 1800, 2000, 2400, 3600, 4800, 9600, and 19,200 baud.

Receive speed is independent of transmit speed; the terminal may receive data at one speed and transmit data at a different speed.

Screen Background

This feature allows the operator to select the background of the screen display. In the normal screen mode, the display contains light characters on a dark background; in reverse screen mode, the display contains dark characters on a light background.

Screen Brightness

Unlike most video terminals, the VT100 does not contain switches or knobs to adjust screen brightness. Instead, the VT100 electronically controls screen brightness. This feature eliminates the high failure rate of mechanical controls and still allows the operator to select the desired level of brightness for maximum comfort under varied lighting conditions. This setting may be saved like any other feature in the terminal.

Scroll

Scrolling is the upward or downward movement of existing lines on the screen to make room for new lines at the bottom or top of the screen. It can be performed in two ways: jump scroll or smooth scroll. In jump scroll mode, new lines appear on the screen as fast as the computer sends them to the terminal. At the higher baud rates, the data is very difficult to read due to the rapid upward movement of the lines. In smooth scroll mode, a limit is placed on the speed at which new lines of data may be sent to the terminal. Upward movement of lines occurs at a smooth steady rate allowing data to be read as it appears on the screen.

NOTE
Smooth scroll mode allows a maximum of six lines of data per second to be added to the screen. The auto XON/XOFF feature must be enabled and supported by the host computer to ensure that data is not lost when smooth scroll mode is enabled.

Tabs

The VT100 can jump or tab to preselected points on a line just like a typewriter. The tab stops may be individually changed or totally cleared and then reset.

Transmit Speed

Transmit speed must be set to match the computer receive speed. The VT100 can transmit at any one of the following preselected transmit speeds: 50, 75, 110, 134.5, 150, 200, 300, 600, 1200, 1800, 2000, 2400, 3600, 4800, 9600, and 19,200 baud.

Transmit speed is independent of receive speed; the terminal may transmit data at one speed and receive data at a different speed.

Wraparound

When this feature is enabled, the 81st or 133rd character (depending on line size selected) inserted on a line is automatically placed in the first character position of the next line. If the wraparound feature is not enabled, the 81st or 133rd character and all following characters are overwritten into the last character position of the current line.

[3] (shifted)

The VT100 contains character sets for the U.S. and the United Kingdom. The difference between the two sets is one character, the # or £ symbol. When the standard U.S. character set is selected, the uppercase 3 key on the main keyboard displays the # character. The £ character is displayed when the U.K. character set is selected.

Part 4 Self-Testing the VT100

A self-test mode in the VT100 automatically, or on command, tests the condition of the terminal if a fault is suspected. The self-test program checks the following items.

This test is performed automatically whenever the terminal is turned on.

Self-Test Error Codes

There are two broad categories of errors: fatal and nonfatal. Fatal errors cause the terminal to immediately stop all operations. No intelligible information is displayed on the screen, but the screen most likely contains a random pattern of characters. The only error indication (in addition to random characters) is a possible error code displayed on programmable keyboard LEDs L1-L4. However, no terminal function, including the lighting of LEDs, is guaranteed if a fatal error is found. See Table 2-3.

Nonfatal errors do not halt the terminal processor. Instead, the terminal is forced to LOCAL mode and an error code character is displayed in the upper-left corner of the screen. There are five types of nonfatal errors:

  1. Advanced Video Option data RAM (AVO)
  2. Nonvolatile data RAM checksum error (NVR)
  3. Keyboard missing or malfunction (KBD)
  4. Data loopback error (Data)
  5. EIA modem control lines loopback error (EIA).
NOTE
Loopback tests are not performed on power-up; they must be invoked separately with the proper escape sequence. See Appendix A for further information on this test.

Table 2-4 shows the possible nonfatal error characters that may appear on the screen and the failure represented by each character.

If the terminal passes all these tests, a final check of its operation is possible in SET-UP mode. Examine the display and compare it with the printed examples. Double height, double width, bold, blinking, reverse, etc., are all represented in SET-UP mode.

Table 2-3 Fatal Displayed Error Codes
Keyboard LEDs Error Replace FRU
L1 L2 L3 L4
OFF OFF OFF ON ROM 1 Terminal controller
OFF OFF ON OFF ROM 2 Terminal controller
OFF OFF ON ON ROM 3 Terminal controller
OFF ON OFF OFF ROM 4 Terminal controller
OFF ON OFF ON Main Data RAM Terminal controller
Table 2-4 Nonfatal Displayed Error Codes
Char Faulty Module
AVO NVR KBD Data EIA
1 X        
2   X      
3 X X      
4     X    
5 X   X    
6   X X    
7 X X X    
8       X  
9 X     X  
:   X   X  
; X X   X  
<     X X  
= X   X X  
>   X X X  
? X X X X  
@         X
A X       X
B   X     X
C X X     X
D     X   X
E X   X   X
F   X X   X
G X X X   X
H       X X
I X     X X
J   X   X X
K X X   X X
L     X X X
M X   X X X
N   X X X X
O X X X X X

Part 5 What to Do in the Event of a Problem

If it appears that there is a problem in the terminal, you should initiate the self-test procedure. This test will help to determine if the problem lies in your terminal or in some other part of the computer system. If the terminal appears to be faulty, refer to Table 2-5. This table describes the items an operator can check prior to making a service call.

Table 2-5 Problem Checklist
Symptom Possible Cause and Corrective Action
VT100 will not turn on when power switch is set to ON. AC power cord not plugged into wall outlet; plug in cord.
AC power cord not plugged into terminal; plug in cord.
Power not coming from wall outlet; check outlet with known working electrical device (a lamp). If no power, call your electrician.
AC line fuse blown. Turn terminal OFF and have the fuse replaced. (See Figure 1-2 for location.)
No keyboard response Keyboard cable not plugged into monitor; plug in keyboard cable.
KBD LOCKED indicator on; computer has turned keyboard off. If condition persists, check with the host computer software people for a possible operating error.
Perform the self-test operation.
Garbled characters Transmit and/or receive speeds, parity sense, or parity enable may be wrong; check settings.
Perform the self-test operation.