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VIDEO DISPLAY REQUIREMENTS
Introduction
The USC/Information Sciences Institute is interested in
purchasing a CRT terminal system to be used in conjunction
with the ARPA computer network. The terminals will be part
of the user's office environment and will be used as any
other tool (e.g. telephone) by the staff in the performance
of their duties. Most of the offices are in close proximity
to a communication processor (which is interfaced to the
ARPANET) in a clustered environment; however, a remote
capability is required.
The basic terminal should consist of a high quality TV
monitor and keyboard with required control logic. The
predominant use of the terminal will be for text
(alphanumeric) communication with TENEX: however, a quality
graphics capability is also required. The problem, which
should dictate the architecture of this display system is
how to provide high quality graphics to a limited number of
terminal users without prohibitively taxing, in dollars or
capabilities, the text-only users. The graphics requirement
has two aspects: a limited and unlimited number of vectors.
If economically feasible, all display controllers should be
provided with a limited graphics capability. The graphics
requirement assumes compatibility with a variety of input
devices (e.g. light, pen, tablet, mouse,etc.) which can be
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added to the terminal as required.
Impiled in the statements of requirements and
performance of the display system is knowledge of the state
of the art of graphics systems. This should not deter the
vendor from suggestions for improving performance.
Consideration of response to this RFP will only be
given to digital systems of a high resolution raster scan
display. The raster scan is required to insure a
flicker-free display without concern for the display
content. The resolution of the system must display a full
page of text (typed, single space, approximately 4,000
characters). The high resolution of the display is also
needed for the quality of vectors desired. The stipulation
of an all digital system is consistent with a requirement
for maintainability and reliability. It is also assumed
that a quantized video display produces better images,
simplifies the video distribution system and the TV monitor,
takes advantage of current digital technology, and makes
more feasible an all solid-state approach, simplifies the
registration problems with input devices, and is more
compatible with a desired modular building blook approach.
An additional goal for the display system design is
production of a terminal that minimizes the required
centralized equipment. This results in minimizing the
differential per unit cost of single and multiple terminal
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clusters. With a minimum of required centralized equipment,
the goal of terminal remoteness can better be realized. For
the most part, the required terminal configuration will be
in close proximity to the interfacing communication
processor. It is expected that economic considerations may
dictate packaging some of the components in a central unit
or multiplexing some of the logic. This economic advantage
should not compromise the display terminal architecture in
such a way that the stand-alone unit cannot be assembled
from the same set of building blocks. The control commands,
character and vector order codes shall be identical for both
the local and remote teminals.
The computer terminal system developed as a result of
this procurement will be a high quality state of the art
instrument for the computer's user environment. It is
within the charter of this institute to assist in providing
improved products for general use throughout the industry.
Therefore, in selecting a vendor to produce this display
system, consideration will be given to the vendor's ability
not only to produce this prototype system, but also to the
survivability of the product should it be in demand by
others.
VIDEO TERMINAL SYSTEM REQUIREMENTS
The clustered video terminal system is perceived as a
collection of building blocks, all available on demand and
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shared by the users via automatic control. These blocks
consist of the TV monitors, character generators, vector
generators, refresh memories and interface controls (see
Fig. 1). The TV monitor shall have a raster format of
1,280 points per line and 864 visible lines. The raster
shall be 2 to 1 interlaced and operate with composite video
(separate sync may be considered) with EIA sync standards.
The monitor shall operate with either black or white video,
with the predominant use to be black on white. The
generators are interfaced to the computer system with up to
19.2K bits/sec teletype-like (EIA RS-232C) channel. These
ports will be provided by a communications processor to be
interfaced to the ARPA network. The generators are
dynamically tied to the terminal through a video switch and
video distribution system as required by the user. The
raster refresh memory is also an on-demand resource and is
only required for the full graphics user.
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********************************* *
* * * *
PDP-10 * * INTERFACE MESSAGE * * ARPA
*<----->* ****
TENEX * * PROCESSOR * * NETWORK
* * * *
********************************* *
/ *
*
*
* /
*********************************
* *
* COMMUNTICATIONS *
* PROCESSOR *
* *
*********************************
/ * *
* 20 19.2 KBIT *
* PORTS *
* * /
* *************************************************
* * . . . . . * 20 CHAR GEN
********* . RASTER GENERATORS . * 20 VECT GEN
* * * . . . . . * 4 RASTER BUF
* * *************************************************
* * *
* * VIDEO OUT - 20 LINES *
* * *
* * * /
* *************************************************
* * *
* * VIDEO SWITCHES (20 X 40) *
* * *
* *************************************************
* * *
* * *
* * *
* ******* *******
* * * * *
* * * * *
********* * 40 TERMINALS * *
*.....*. . . . . . . *.....*
******* *******
FIGURE 1: BLOCK DIAGRAM OF A VIDEO DISPLAY SYSTEM - CLUSTERED
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CHARACTER GENERATORS
Twenty character generators consisting of a font
memory, character buffer, and control logic shall be
provided. The operation of these generators produces
characters "on the fly" in synchronism with the raster of
the TV monitor.
The character generator shall produce 80 characters of
fixed spacing per line, and 54 lines of text. The total
addressable raster (for 16 x 16 bit characters) is,
therefore 1,280 x 864 points. The font memory shall have
256 symbol descriptions simultaneously available for
character generation. These memories shall be writable at
speeds compatible with the communications interface. The
font memory shall consist of a 16 x 16 bit matrix for each
symbol which includes character spacing, line spacing, and
an addressable point for every point in the raster matrix
for a given character position. This is necessary so that
symbols can be constructed with multiple characters (e.g.,
straight lines appear continuous from character space to
character space). Flexibility in character fonts is
required, and any one of a number of known techniques to
implement this is acceptable.
The aspect ratio of the character shall be 2 to 1,
length to width, so that the density of the addressable
display points is also 2 to 1. These bit densities are
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required to produce the required fonts as well as minimize
the calculations for vector generation. The character
buffer shall store the 8-bit ASCII characters at a rate up
to 19.2K bits, per second, as required by the interface
logic. The buffer capacity shall be 4,320 8-bit words.
VECTOR GENERATORS
Vector generators shall be of two types: limited and
unlimited capacity. Twenty limited vector generators are
required. The limited vector generator shall be capable of
presenting 128 vectors per display frame time (60 Hz) in
synchronism with the interleaved raster display. Vector
order codes, specifying end points in X and Y , shall be
received unordered at rates up to 19.2K bits per second and
stored in vector buffers. The vector generator shall
generate video, as required, to depict the line to the best
fit of the addressable points. Vector length for the entire
diagonal of the display area shall be allowed. Vectors
shall be selcetively erased by removal from the vector
buffer. It is desirable that vectors, or strings of
vectors, carry tags for identifying the vectors to be
erased.
The unlimited vector generator shall employ the vector
generator described above as a component, with additional
components to increase the vector capacity to at least 4,000
vectors. If vector length is a sensitive parameter in the
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design of the vector generator, the vectors shall be
considered to be one inch. The use of raster storage (1,280
x 864) is one way of achieving unlimited vector capability.
Four unlimited generators shall be required with the ability
to switch the generator to any of the 40 terminals.
Techniques using increased vector buffers in combination
with vector generators are also acceptable to achieve
unlimited vector capability. In the latter case, the
quantity of generators required will be dictated by economic
factors.
TERMINALS
The current requirement is for 40 terminals. The
terminals consisting of high quality TV monitors and
electronic keyboards, shall be packaged suitable for office
installation. Although the specifics of the display quality
are not being detailed, the quality of the TV monitor is of
extreme importance. The specifications of the display
surface, light output, spot size, distrotion, etc. are
expected with the response to this RFP. The terminal
design, appearance, and human factors consideration must be
approved by the Institute. The TV monitor shall be
primarily used in black on a white background. It is
desirable to have a switch for white on black display. The
digital video does not require gray levels.
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The keyboard shall include the completee ASCII
character set, the keyboard shall provide some type of
tactile feedback when striking keys. Feedback shall
indicate a keystroke has occurred. Some form of key
contention roll-over is required. N-key roll over is
desirable.
Terminal mobility shall be provided by use of a
wheel-type typewriter stand or a wheeled integral base if
necessary.
The vendor's proposed design should consider the
ability to use these same building blocks with a remote
stand-alone terminal. This configuration shall require the
EIA RS 232C type interface at a switchable rate from 300 to
19.2K baud.
Additional elements required in the suggested
configuration are video switches. The video connection to
the terminal is not part of this RFP.
The video switch is required to dynamically connect 20
generators to 40 video output jacks. The switch is
controlled by terminal demand and whenever an assignment is
made, the selected switch shall remain until the user
becomes inactive (logged out). The switch must function in
much the same manner as a line finder, as in telephone
terminology. This means responding to the terminal's
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request for service by providing one of the 20 video
generators. The requesting signal may be a tone, keyboard
input, continuous polling, a D.C. level change, etc. A
busy response of a tone or light shall be provided when all
video generators are in use. The 20 generators shall also
be available via another switch to the 4 refresh memories.
The output of the 4 refresh memories shall be made available
to any of the 40 video output jacks of the switch in
response to a terminal request. Refresh memories are
synonymous with unlimited vector generators.
The video drivers must be capable of driving 300' of RG
59/U and producing a signal compatible with the monitors'
input requirements and display quality.
The communication interface shall use the full ASCII
character set, full duplex, 8-bit bytes, asynchronous up to
a 19.2K bits/sec rate. An alternative of variable input
rates for the keyboard, of 300 to 2,400 bits/sec, may be
considered.
DESIRABLE ATTRIBUTES
The performance requirements of the terminals, as
stated above, can be improved in a variety of ways,
depending on economic considerations. There are, however,
additional highly desirable attributes for the Institute's
applications which could be included in the proposal. These
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are:
* The 40 terminals and 20 generators required at
the present time may soon be insufficient. The system
should be open-ended to allow for growth of additional
terminals or generators, without making existing
hardware obsolete.
* A two-page display of approximately 8,000
characters on a single screen.
* Variable character spacing up to a maximum of
100 characters per line.
* Consideration of future expansion of character
capacity up to twice the present size. These 256
character descriptions will be performed with a full
8-bit ASCII character set.
* Line width control, rather than gray level or
color for video modifiers.
* A monitor switch for compatibility with
standard commercial video (525 line).
* If separate sync for the computer display is
proposed, the standard TV mode switch shall also solve
the sync problem for the 525 line display.
DOCUMENTATION
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The procurement of the terminal system shall also include
documentation sufficient for maintenance and future
expansion or modifications of capabilities. This
documentation shall include a verbal description, logic and
schematic diagrams, and specifications and/or vendor part
numbers for all the elements and sub-assemblies used in the
fabrication of the terminal systems. The documentation
shall be of commercial quality with consistent logic and
flow diagram symbology.
(Figure 2.)
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*************************************************
* * *
* * *
* CHARACTER/ * TERMINAL *
SERIAL * VECTOR * *
DATA * GENERATOR * *
******** * *
300 - * *************************
19.2K * * *
BITS * * *
*************************************************
FIGURE 2: BLOCK DIAGRAM OF STAND ALONE TERMINAL