VT52 DECscope Maintenance Manual

Chapter 1

1.1 General Description

The VT52 Video Display Terminal (Figure 1-1) is a 24-line, 80-character display terminal that serves as an input/output device to a host processor. It transmits and receives data at speeds up to 9600 baud. The main keyboard uses a standard typewriter layout that supplies upper- and lowercase alphabetic characters as well as numeric, symbol, and control characters to a host. A 7 × 7 dot matrix is used to form the displayable characters. All input, output, and display operations are controlled by a ROM resident microprogram.

VT52 Video Display Terminal
Figure 1-1 VT52 Video Display Terminal

1.2 Features

Design features of the VT52 include a 19-key auxiliary keyboard for applications requiring much numeric input, and a Hold-Screen mode for operator control of processor files. These and other features are described in the following paragraphs.

1.2.1 19-Key Auxiliary Keypad

This feature allows the operator to use the convenient 19-key numeric pad in applications requiring much numeric input. In one mode, numeric keys from the pad transmit the same code as numeric keys from the main keyboard. In the Alternate-Keypad mode, each key transmits a unique Escape Sequence that is used to invoke a user-defined function.

The three blank keys on the pad also transmit a unique Escape Sequence and can be defined by the customer for his own particular application.

Four cursor control keys transmit unique Escape Sequences that will move the cursor one position UP, DOWN, LEFT, or RIGHT, in the direction of the arrow, if the code produced by the key is echoed back to the terminal by the host.

1.2.2 Hold-Screen Mode

The Hold-Screen mode allows the operator to regulate the speed of the data received from the host and displayed on the screen. Normally, the host transmits data at a rate that is too fast for the operator to read; as the host adds new information to the bottom line, the information on the top line is scrolled off and lost forever to the operator. When in Hold-Screen mode, the terminal will not process information that would cause a line scroll until requested to do so by the operator. The operator can request a new line of characters by typing SCROLL or a new screenful of characters by typing SHIFT, SCROLL.

1.2.3 Direct Cursor Addressing

Direct cursor addressing allows the host to move the cursor to any position on the screen by transmitting an Escape Sequence to the terminal. Cursor positioning commands are defined in Chapter 3.

1.2.4 Identification Feature

This feature allows the host software to poll every terminal on the system, requesting each to identify itself. The VT52 will automatically respond with a 3-character Escape Sequence that identifies it as a VT52. This allows the VT52 to be mixed with other terminals in a system with the software responding correctly to each different type of terminal.

1.2.5 Terminal Interface

The VT52 is available with either the 20 mA current loop interface or, if ordered by the customer, a standard EIA interface.

1.2.6 Copier Option

An electrolytic copier is available to provide hard copy capability to the terminal. The copier can print a screenful of information or print the information one line at a time.

1.2.7 Printer Interface Option

The Printer Interface Option VTXX-KA is a field installable option available on all new VT52s and certain units already in the field. It provides a data path between the VT52 Video Terminal and a serial or parallel printer such as the LA36 or LA180.

1.3 VT52 Specifications

Dimensions Height: 360 mm (14.1 in)
Width: 530 mm (20.9 in)
Depth: 690 mm (27.2 in)
Minimum Table Depth: 450 mm (17.7 in)
Weight 20 kg (44 lbs)
Operating Environment DEC STD 102 – Class B Environment
10°C to 40°C (50°F to 104°F)
Relative Humidity 10% to 90%
Maximum Wet Bulb 28°C (82°F)
Minimum Dew Point 2°C (36°F)
Line Voltage U.S. model: 100-126 V (115 V nominal)
European model: 191-238 V or 209-260 V (220/240 V nominal switch selectable)
Line Frequency U.S. model: 60 ± 1 Hz
European model: 60 ± 1 Hz or 50 ± 1 Hz
Power Consumption 110 Watts
Power Line Hash Filter Low-leakage Balun type
Format 24 lines × 80 characters
Character 7 × 7 dot matrix
Character Size 2.4 mm × 3.4 mm (0.08 in × 0.16 in)
Active Display Size 218 mm × 114 mm (8.6 in × 4.5 in)
Character Set 96-character displayable ASCII subset (upper- and lowercase, numeric, and punctuation)
Character Set Complete 7-bit ASCII set (128 codes)
Key Layout Typewriter – rather than keypunch – format; 63 keys
Auxiliary Keypad 19-keys: numerals, cursor-movement, three user-definable function keys
CAPS LOCK Key Locks alphabetic keys to uppercase state, but does not affect non-alphabetic keys
Audible Signals
Key-Click Keyclick sound simulates typewriter
Bell Sounds (1) upon receipt of control characters BEL; (2) when keyboard input approaches right margin (output from host approaching right margin does not cause bell to ring)
Page Overflow LF causes upward scroll.
Parity Even or mark (no parity) switch-selectable; odd or space possible with rewiring. (Note that received data is not checked for parity error)
Type Blinking underline
Control Up or down one line, right or left one character, home, tab (fixed tab stops every eight spaces), direct cursor addressing (allows cursor to be moved to any character position on the screen)
Functions Erase display from cursor position to end of line; erase to end of screen; scroll up
Hold-Screen Mode Allows operator to halt transmission from host, preserving data on display. Operator can request new data, line- or screenful-at-a-time; enabled/disabled by Escape Sequences sent by system software.
Terminal Self-Identification Terminal transmits on command a sequence unique to its model; software can identify features available on any terminal it is in contact with.
Communications 20 mA current loop or EIA interface; specify at time of order.
Code USASCII extended through Escape Sequences
Baud Rates Switch-selectable
Transmission Rates Full duplex (switch selectable) 75, 110, 150, 300, 600, 1200, 2400, 4800, and 9600 baud
Switch-selectable local copy
Synchronization Automatically transmits control codes to host, requesting suspension and resumption of transmission, when unable to process data
Operator Controls Power On/Off, Intensity Control, Baud Rate Switch, Terminal Mode Switch, Even/No Parity
Overload Protection Thermal cutout (circuit breaker)
Case Material Injection-molded Noryl thermoplastic
Screen Phosphor P4

1.4 Documentation Ordering Information

The following VT52 DECscope Video Terminal hardware manuals can be purchased from Digital’s Accessory and Supplies Group:

Title Document No.
FB-VT52 VT52 DECscope Maintenance Documentation Package
EK-VT5X-OP-001 DECscope Users’ Manual

All purchase orders, invoicing inquiries and correspondence should be forwarded to:

Digital Equipment Corporation
Cotton Road
Nashua, New Hampshire 03060
Attention: Accessory and Supplies Group