Note: Descriptions are shown in the official language in which they were submitted.
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TERMINAL INDEPENDENT COLOR M13MORY
FOR A DIGITAL IMAGE DISPLAY SYSTEM
This is a division of cop ending Canadian Patent
Application serial number 403,146 which was filed on May
18, 19820
This invention relates to digital image display
systems and, more particularly, to a terminal independent
color memory for such systems.
Methods and apparatus for utilizing digital
techniques to provide color images on video display
screens are well known. A problem, however, has arisen
in that computability among digital display systems has
been made difficult by the great variety of methods and
apparatus for providing the color images. For example,
one available system utilizes a specific color value
selection method; viz., a direct selection ox data values
corresponding to the primary colors - red, green and blue,
while other systems employ a technique for specifying both
a foreground and a background color by indexing a
permanent, "read only" color memory.
The art of color computer graphics generally
employs a color look-up table or color map indexed by a
binary number to expand the repertory of colors available
for display. One such terminal is capable of providing 8
colors for current use from 64 possible color values
stored in its color map.
Other features, such as blinking, i.e., the
ability to alternate between two visual attributes, may be
provided by these terminals. However, the various methods
and apparatus for providing such features are similarly
incompatible.
With the advent of services known as teletext and
videotext or view data, wherein a customer is able to gain
access to a remote host computer and associated data base
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from a digital image display terminal, there has arisen a
need to solve the problems presented by incompatible
terminals.
Summary of the Invention
In accordance with an aspect of the invention
there is provided a digital image display system,
comprising: a color memory for storing color data values;
processing means responsive to a particular command and
data sequence providing a blinking of certain picture
element data from one particular color specified by the
data sequence to another particular color specified by the
data sequence by periodically changing color data values
in the color memory, multiple color blinking processes
being provided responsive to multiple commands, each
process subsequent to a first process being in delay
relationship to the next previous process; and a display
means for displaying the multiple color blinking
responsive to the processing means.
In accordance with another aspect of the invention
there is provided in a digital image display system, a
method for providing a blinking of certain picture element
data from a particular color to a particular color, the
method characterized by the steps of: specifying multiple
blinking processes, each color blinking process including
providing a blinking of certain picture element data from
one particular color specified by the data sequence to
another particular color specified by the data sequence by
periodically changing color data values in the color
memory; specifying a delay interval if desired, between
the processes; and displaying the multiple color blinking.
These problems are solved by the use of an unique
process in a terminal independent color memory. Processing
means are provided for accessing color data in a terminal
independent manner, regardless of the size of color memory
at a terminal or its permanent or semi-permanent nature.
Known modes of color access are incorporated into the
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process for selecting a particular mode of color memory
access, for setting a particular color in a color map or
for setting foreground or background colors available for
current use (in-use colors). These in-use colors then are
applied by subsequently received text and graphics drawing
commands. In a system having a permanent color memory,
the closest color to the desired color hue is selected
from the permanent color selection table.
The content of the color map is established by
selecting a gray scale equally spaced between black and
white and hue data values equally spaced about a hue
circle wherein the primary colors are located in 120
degree relationship. In this manner, a host computer is
able upon initialization of the terminal independent
color memory, to predict the configuration of a particular
color map and the color composition of a digital image or
frame of information for display.
Color blinking is provided by means ox a linked
list of multiple processes. The on and off intervals of
blink-from colors and blink-to colors may be specified.
In addition, the delay between processes is selectable
Simple animation is possible with the present technique.
For example, a ball may appear to bounce across an image,
a river may appear to flow or stars may appear to twinkle.
grief Description of the Drawings
The present invention taken in conjunction with
the invention disclosed in cop ending Canadian Patent
Application serial number 403,146 which was filed on May
18, 1982, will be described hereinbelow in detail with the
aid of the accompanying drawings, in which:
FIG. 1 is a general block diagram of a digital
image display system which may employ the principles of
the present invention, the system being exemplary of
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arrangements for color processing;
FIG. 2 is an operational diagram of the process
for selecting a color data value from a color map for
display of particular picture element data;
Fugues 3, 4, and S are flow diagrams of a method
for accessing color data values for display regardless of
the mode of access employed by a particular digital image
display system in accordance with the present invention;
FIG. is a representation of a color hue circle
wherein the primary colors - red, green and blue - are
- located at 120 degrees, 240 degrees and 350 degrees
respectively;
FIG. 7 is an exemplary table of color data values
selected in accordance with a method for initializing a
color map in a terminal independent manner in accordance
with the present invention;
Fugues 8 through 14 generally depict the present
method for providing Inultiple processes of color blinking
in accordance with the present invention;
FIG. 8 is a depiction of the contents of a memory
block associated with a particular blink process
FIG. 9 comprises blink process tables indicating
the logical connection of linked lists of active and free
process blocks as depicted in FIG. 8;
FIG. 10 depicts an active blink process table
comprising a plurality of process blocks as depicted in
FIG. 8;
FIG. 11 is a flowchart of a method for providing
multiple process color blinking;
FIG. 12 is a flowchart diagram of an algorithm
for adding a new process to the active blink process table
of FIG. 10;
FIG. 13 is an exemplary timing diagram and color
tables for a color blink comprising three processes; and
FIG. 14 is an exemplary blink process table
similar to that depicted in FIX. 9 whose process Emory
block entry valves are shown relative to a particular point
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in the timing diagram ox JIG. 13.
Detailed Description
Referring more particularly to FIG. 1, there is
shown a general block diagram of a digital image display
S system employing the principles of the present invention.
The digital image display system comprises a data
processor 1 having bidirectional access to a processor data
bus 2. A separate timing generator 3 may provide the clock
sisals required on the processor data bus 2; however, in
some systems, the timing generator capability is provided
by data processor 1. The timing generator 3 may also
provide the timing signals on a video data bus 8 for use by
video memory 4, and by a video controller 6. The video
controller 6 operates video display 7 responsive to the
picture element data received over the video data bus 8.
The picture element comprises a binary index for selecting
color data values from color map pa. Complete digital
images or frames 5 of picture element information are
sequentially displayed in color by video display 7.
Data processor 1 may be a microprocessor
comprising read-only memory 3 and random access memory 10.
In a view data or teletext terminal which may be located in
a residence, it is desirable that data processor 1 be as
small as possible; accordingly, a microprocessor may be
assured.
Data processor 1 responds to user input from, for
example, a keyboard, keypad, joystick or floppy disc via
leads 18-21, respectively, or from other data input devices
known in the art through peripheral device interface 17.
In accordance with known technology, data processor 1 may
program the video memory 4, the timing generator 3 and the
video controller 6 to the proper modes ox operation which
will allow maximum flexibility in remotely reconfiguring
the terminal operating characteristics.
In its application with a view data or teletext
terminal, the data processor 1 may also respond to input
provided prom a remote or centralized data base such as one
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located at a television broadcast station or a provider of
view data services. Such inputs art provided through
communications interface 12. In the case of teletext
services, a TV broadcast signal I is received at interface
12 via receiver 14. In the case of view data services, data
is provided over a communications line 15 and through a
data modulator/demodulator 13 to interface 12.
Input/output controller 11, under user control, provides
selectable access to the various data input and output
arrangements.
Processor data bus 2 is a bidirectional conduit
through which the data processor 1 controls the video
memory 4, the timing generator 3 and the video
controller 6. The bus generally comprises address
capability, a data path and control lines which may include
interrupt, reset, clock (for synchronous use), wait (for
asynchronous use), and bus request lines.
The timing generator 3 may comprise a chain of
programmable logic circuits, digital dividers and counters
for providing required timing signal outputs. For
operation of the video data bus 8, a number of different
timing signals are required. Horizontal and vertical drive
signals are provided in accordance with horizontal and
field rates respectively. A dot clock signal is provided
at the dot frequency picture element or pot rate) of the
system. An odd/even field signal indicates if the odd or
even field is to be displayed in an interlaced system. A
composite blanking signal indicates if video is being
displayed or if vertical or horizontal retrace is
occurring. Also, a group clock signal or other signals may
be provided. The group clock signal indicates when to
access data for a new group of picture element data from
memory. For example, picture element (pot) data in video
memory having a slow access time may be serially provided
in groups of 4, or 16 picture elements. On the other
hand, a parallel data transmission scheme is possible,
potentially increasing the requirements for leads of video
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data bus 8.
Controller O accepts digital image information
from bus 8; pel-by pot, and converts the digital
information, if necessary, to analog form for presentation
on video display 7. Controller 6 comprises three
components: 1) color map Gay 2) digital to analog
conversion and sample and hold circuits (not shown), if
required by video display 7; and 3) a standard composite
video encoder (not shown), for example, for providing
standard video or red, green, blue (RUB) outputs.
Color map pa comprises a random access memory
indexed by a binary number component of pot data entering
controller 6 by way of bus I. For example, if four bits of
color data are compiled per picture element, 16 color
Cassius are directly accessible from color map pa. Each
indexed choice may comprise, for example, 12 bits of RUB
data, tile domain of possible data values in this case being
4096 possible values. The color map pa may be loaded and
updated from the large repertory of possible choices by
processor 1 under local or remote control.
Memory 9 may contain a directly accessible color
table. Selections of color data values from memory 9 are
transferred to color map Spa for subsequent use. Also,
memory 10 may contain a color memory, color data similarly
being transferable to color map pa. Various modes of
access to color memory, wherever located, in a digital
image display system, are employed by the providers of
view data and teletext services. Means for providing
terminal independent color memory will be subsequently
discussed in connection with Fugues 3-14.
The color map RUB output may be provided to three
separate digital to analog converters, one for each primary
color. The RUB output may enter display 7 directly, may
first be converted to a composite video signal or be
modulated to a particular OF frequency for input through an
antenna lead-in.
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Video display 7 may be a monitor, a television
set, a video projection system, a liquid crystal display or
an LED display. The list is not intended to be all
inclusive and, if another standard forlnat of input video
signal is required, the principles of the present invention
assume the capability of controller 6 for providing such a
standard video signal.
Memory 4 comprises random access memory for
storage of video picture element information for display.
In particular, memory 4 generally accepts input from data
processor 1 in the form of an image comprising digitized
picture element information. Memory 4 stores the
information until rearrangement of data occurs and
periodically passes the pot information over bus 8 to
controller 6 on command of processor 1. As previously
; indicated, the pot data comprises binary data employed to
index a particular color entry in color map pa.
Gus 8 connects generator 3 and memory 4 to
controller 6. It comprises data leads for picture element
; 20 information which is used for indexing the color map pa,
and timing leads for providing video timing and control.
The six timing and control leads include the previously
mentioned horizontal and vertical drive signals, the dot
clock, the field signal, the composite blanking signal and
the group clock signal.
Referring more particularly to FIG. 2, an
operational diagram is shown Wylie depicts how a binary
number cor.lponent of picture element data stored in memory 4
indexes color map pa so that primary color data values for
a video signal are provided for video display. Similar
reference characters have been employed in Fugues 2 through
14 and in the subsequent discussions wherever possible. In
addition, the first numeral of reference characters
employed in Fugues 2 through 14 relates to the location
where the referenced element first appears.
In the depicted example a color map of 16 colors
is shown. The capacity of the color map may comprise, for
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example, four bits each of red, Green and blue data. The
total twelve bit capacity Tulane relates to 4096 possible
colors. accordingly, cacti of the 15 tabular values indexed
comprises 12 bits of RUG data.
S In the depicted example, picture element data 201
identifies the coordinate location in a particular image or
frame 5 for display and specifies the binary index value
representing the desired color for picture element 201.
Binary index value 1011 representing the twelfth entry in
the color map may, for example, represent color data value
0011 1111 0000; 0011 being red data; 1111 being green data,
and 0000 being blue data. The RUG data value, as
previously discussed, illuminates the corresponding
coordinate location in the particular in-use color in
frame S of display 7.
Upon command of a remote host computer, 16
specific colors May be stored in color map 6â by processor
1 instructions stored in memory 9. Processor 1 may also
load the color map under control of local keyboard input.
Either the host computer or the local user may store colors
directly in color Map pa from memory 9 or from a semi-
permanent memory 10 with color data values for use.
Referring to Fugues 3, I, and S, flow diagrams
depict the method in accordance with the invention for
accessing color map Ox in a terminal independent manner and
for setting the foreground and background colors available
for current use. FIG. 3 represents a command decoding
process. If a first particular command is found, the
sequence depicted by the flow decorum of FIG. 4 is
performed within processor 1. If a second particular
command is found, then the flow diagram of FIG. S is
followed. Other commands are interpreted by the command
decoding process depicted in FIG. 3. These other commands
may include commands to perform the subsequently described
color blinking process or other- text or graphic drawing
processes
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referring particularly to I 3, the data
processor is instructed (box 301) to attempt to locate the
next opaqued. The command May be received from a remotely
located host computer or locally through the peripheral
device interface 17. At decision box 302, processor 1
determines if the command entered is one for selecting a
node of color memory access. it box 03, transfer is
effected to the mode selection process shown in FIG. 4 if
there is a match. If there is not a match, the data
processor determines at decision box 304 whether the
command entered is one for setting a color data value. At
box 305, transfer is effected to the color setting process
shown in FIG. 5 if there is a match. In a similar manner,
the entered colnmand may be composed with other valid
commands 306 and the entire command recoding process
repeated.
; Referring to JIG. 4, a process for selecting a
mode from a plurality of modes of color memory access and
for setting foreground and background in-use colors for two
of these modes is shown in flowchart form. Having
transferred control to box 401 of FIG. 4 from the flowchart
of FIG. 3, processor 1 now interprets the operands or data
following the command. In general, it is presumed that a
command will always be followed by a sequence of operands
or data entry or a new command. Accordingly, in the
process depicted in FIG. 4, the data operands are
interpreted and, as a result, the mode of access and the
background and foreground colors are set, if possible.
In particular at box 402, the first data operand
is recovered, if possible. If at box 403 an operand is
located, another attempt is made at box 404 to locate a
second operand. If at box 407 a second operand is found,
the color mode of access is set at box 411 to mode 2. In
other words, the color mode is determined by the number of
us operands following the command for selecting the mode of
access. Accordingly when no operands are found, the color
mode is set at box 405 to Mohawk 0. If one operand is found,
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the color mode is set at box 40~3 to mode 1.
In color mode 0, besides setting the color mode,
it may be necessary in systems employing Emory 10 to
reinitialize memory Go to a default set of color data
values. Accordingly bloc 406 suggests this activity if it
may be performed. Color mode 0 of the present terminal
independent color memory is adapted for use in digital
image display systems employing a direct color selection
process either from permanent or semi-permanent color
memory.
After setting the color modes to 1 or 2 at
blocs ~08 or 911 respectively, the foreground and
background in-use colors are set. If foreground and
background colors may be set in color mode 0, the
subsequently described process of FIG. 5 performs this
task. In color Mode 1, only picture element data of the
actual character in video err is drawn in the current
in-use foreground color without illuminating adjoining
picture element data in a background color. In color mode
2, text characters will be drawn in the in-use foreground
color over the in-use background color. In other words, a
character may fill a rectangular field on display I The
actual character is illuminated in foreground color as in
color mode 1, and the rectangular field surrounding the
actual character is filled with the current in-use
background color.
Hereford, in color rode I the foreground color
is set at box 409 to the value of the first operand At
box 410, the background color is set to a data value
representing "invisible" or no color. In color mode 2 the
data processor compares the first and second operands
entered. of the two operands are equal, then it is assumed
that it is desired to change only the background in-use
color and not the foreground color. Otherwise, the
foreground color is set at box 419 and the background color
is set at box 413 to the first and second operands
respectively. Control is returned at box 415 to the opaqued
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decoder program upon the completion or the color access
sequence.
Fig 5 is a flowchart (1) in color modes 1 or 2,
for setting the color data values in memory pa in a
S terminal independent manner or (2) in color mode 0, for
setting foreground and background colors. At decision box
502, the data processor determines if color mode 0 has been
previously entered. It is assumed that, before the command
for setting a color data value is entered, the select color
access mode command has been read and acted upon in
accordance with the flowcharts of Fugues 3 and 4.
If the color access mode at box 502 is 0, the
first operand is located if possible at box 503. If the
operand is located at box 505, a second operand is located
I if possible at box 507.
If a second operand was not located at box 509,
the foreground color and the background color will be
modified at boxes 512 and 514 respectively. At box 512,
the foreground color is set to the index of the closest
match of the first operand and a color value from table pa.
At box 514, the background color is set to an "invisible"
color. 'Invisible'' it intended to describe the process of
depositing pot values in video memory 4 only at the
character or graphics drawing command locations
corresponding to the foreground of the resulting image and
not over-writing those corresponding to the background.
If a second operand has been successfully located
at box 509 then a check is made at box 511 to see if both
operands are equal If the first and second operands are
equal, only the background color is set at box 515. If the
two operands are not equal at box 511, the foreground color
is set at box 513 and the background color is subsequently
set at box 515. As in the case of a single operand, the
foreground color and the background color are set to the
index of the closest matched color in table pa.
If the color mode was not n at box 502, table pa
will be loaded With colors specified by subsequent
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operands. The current in use foreground color index will
indicate the first potential color map Monroe table entry
to be changed. INDEX is set to the current in-use
Foreground color index at box 501. An attempt is made to
get an RUB operarld at box 50q if possible. If the operand
is found at decision box 506, then the RUG operand is
loaded into table pa at the location determined by INDEX.
The INDEX is then incremented at box 510. The sequence of
boxes 5Q4, 506, 508 and 510 is repeated as long as operands
are available.
Referring to FIG. 6, a color hue circle is shown
wherein the primary colors - red, green, and blue -
are located at 120 degrees, 2~0 degrees and 360 degrees.
Upon the operation of the box 406, FIG. 4, and on other
occasions in the operation of a digital image display
system, for example, an explicit resetting operation, it is
appropriate to initialize or establish table pa regardless
of the number of possible entries and in a predictable
fashion. Accordingly, a method is provided whereby one
half of the color pa? memory in table pa is filled with a
grew scale whose values are equally spaced between black
and white and tile other half of table pa is filled with a
color hue scale whose values are spaced about a hue circle
of 360 degrees.
In particulate, if the number of bits of a binary
number index to table pa is defined as N, then the number
of entries in the color map is ON. Then the quantity 2N/2
of entries comprise grew scale values and the quantity 2~/2
of entries comprise color hue values.
If the capacity of table pa is M bits of data,
the quantity M/3 bits of data represents data for each
primary color - red, green, and blue. In general, the
relationship between I and N is maintained such that M is
greater than or equal to three times the quantity N-l.
By way of example, if a particular color map
mottler is indexed by a 4 bit binary index value, then 8
grew scale levels and hues are loaded upon request into
table pa. The quantity M theta should be treater than or
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equal to I: 3 bits each ox red, Green, and blue data.
In this example the grew scale is between
zoo on zoo and 111 ill ill and is represented by the
binary result of the equation Pi = Cole) where I
represents the decimal number ox grew scale levels,
generally 2N/2, k, a quantity between Oily, is the
particular entry in the map desired, and Pi is the binary
result for a primary color - red, green and blue. It is
most convenient if, in the operation of data processor 1,
the result is truncated to I bits. The value for all the
primary colors is set equal to the truncated result of the
binary division.
FIG. 7 depicts an exemplary color map memory
table. In accordance with the above method, the first
eight values are initialized to grew scale levels in a grew
scale 706 between 000 000 000 at address 704 with the
binary index value 0000 and value 111 111 111 at address
704 with the binary index value 0111.
To provide the color hue values, data processor 1
must first calculate the angle of a desired color nut. If
2N/2 entries are required then the result of the equation 1
... n times 360 degrees divided by 2N/2 provides the angle.
In FIG. 6, if eight hue data values are desired, color data
values are required for 45 degrees, at location 611, 90
degrees at location 612, 135 degrees at location 613, and
so on about the color hue circle.
The data processor must find the location of the
closest primary color angle to the desired angle h, the
next closest primary color and the primary color furthest
from h. For color value 511 at 45 degrees, the primary
color blue at location fool or 360 degrees is the closest
primary color. This result may be established in temporary
memory as variable Pi. The next closest primary color is
red at location 603 or 120 degrees. This result may be
established in temporary memory as variable Pi. The
primary color furthest prom the desired color hue is green
at location fin or 240 decrees. This result may be
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established in temporary memory as variable Pi.
The results Pi, Pi, and Pi, of this calculation
are then el!lployed to establish the color data values for
the primary colors - red, green and blue. As it is known
that Pi is blue in this example, the blue data value in
binary form is set in color map memory as all l bits. As
it is known that Pi is green, the green data value is set
in color map Emory as all 0 bits.
In the case of Pi, data processor l is instructed
to calculate the binary result of the equation:
As it is known that Pi is red, the red data value is set in
color map memory to the binary result of the above
calculation. As with the grew level calculation, it is
generally appropriate that the result be truncated to M/3
data bits in length.
Referring again to FIG. 7, the color hue data
values are entered in address locations 1000 to 1111 in the
depicted exemplary color map memory table. In particular,
the above calculation for a hue at 45 degrees on the hue
circle of FIG. 6 is located at address 1001. As previously
indicated, the blue data value is all 1 bits or 111; the
green value is all 0 bits or 000, and the red value is
given by the binary result 101.
FIG. 8 depicts a memory block associated with the
blink process and identifying its parameters. Each time a
blink process is initiated, a blink process block must be
established in memory which stores the relevant parameters
associated with that process. The first entry 801 in the
block stores the LINK value, which is a pointer to the
starting address of another blink process block. If the
process is active, then the WINK value will point to the
next active process block. If the process is inactive,
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then the LINK value will point to the next FREE process
blocic.
Toe second entry 8~2 in the block stores the
current status of the blink process. The status can be
either INACTIVE ON or OFF (the latter two of which are
considered active states).
The third entry 803 is used to store the BLINK-
FROM COLOR which is a binary number index that acts as an
index into the color map memory table. This index number
is extracted from the operand following command or ox code
representing the color blinking process and does not change
throughout the life of the process.
The fourth entry 8~4 is used to store the SAVE
COLE, which is an RUB value and not a binary index that is
periodically copied out of the color map memory table in a
manner that will be described subsequently.
the fifth entry 805 is used to store the BLINK-TO
COLOR which is a binary number that acts as an index into
the color map memory table. This number is also extracted
from the operand following the blink process ox code and
does not change throughout the life of the process.
The sixth entry 806 stores the ON TIME and the
seventh entry ~07 stores the OFF TIME, both of which are
most conviently numbers between 1 and 64 that represent
time intervals and fractions of a second. These are also
extracted from the operand following the blink process ox
code and do not change throughout the life of the process.
The eighttl entry 808 stores the CURRENT COUNT
- which is also a number that represents a time interval.
This number is updated regularly as the process is
executed.
FIG. gives a logical view of how the linked
blink process blocks are treated. where are two linked
lists kept in memory The first contains all of the active
us process blocks and the second contains all of the INACTIVE
or free process blocks. the rlemofy occupied by the
INACTIVE process blocks is available ion use by new blink
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processes, and hence this list is called the FREE list.
The heat 901 of the ACTIVE list is a single pointer that
contains the address in memory of the beginning ox the
process block of the nicety recently received active blink
S process 902. The LINK entry in this bloc in turn points
to the beginning of the next most recently received active
blink process 903, and so on to the beginning of block 904,
block 905 through the entire list of process blocks that
contain active blink processes. The displaced appearance
lo of the blink process blocks is intended to represent their
random appearance in memory. The last process Lock on the
list contains a LINK value NULL indicating the end of the
list. the head of the FREE list 910 is a single pointer
that contains the address in memory of the beginning of the
lo Process block of the first inactive blink process 911. The
LINK entry in this block points to the beginning of the
next inactive process block 912 and so on to the beginning
of block 913, block 914 through the remainder of the
inactive process blocks. When the system is initialized,
as well as any time that there are no currently active
blink processes, all of the available blocks of memory
allocated to the blink feature are on the TREE list
When a new blink process is initiated, the first
block in FREE list 911 is jade available for its use. When
US this happens, the head of the FREE list pointer 910 is
changed to the address of the beginning of the next free
block 912. Also, the head of the ACTIVE list pointer 901
is changed to the address of the beginning of the block 911
just allocated, and the LINK pointer within block ill is
changed to the address of the beginning of what was the
Yost recently received active blink process block 902. The
new active process block 91l is then loaded with the
relevant ~aran~eters of the blink process being defined.
ERG. lo shows the actual organization within
Mueller of blink Irises blocks. The first entry Lowe and
the second entry 1002 store the Lydia of the ACTIVE list
pointer and head of the Ennui: list pointer, respectively.
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Process blocks are stored in sequential error locations
Lowe through loo or until the capacity allocated within
Ille~ory 10 is reached. These locations do not necessarily
correspond to the order in which the blocks appear on the
linked lists.
FIG 11 shows a flow diagram for TIC, the
primary blink processing subroutine. TIC is periodically
called from a main control program, typically every 1/10 to
second. This subroutine goes through, examines, and
updates each process block (and the color map memory table
if necessary in the ACTIVE list starting with the most
recently received blink process block and proceeding to the
last.
activity block 1101 with which the TICK
subroutine begins, sets the value of an internal status
variable TRY to the address stored in the head of the
ACTIVE list. Tin as described previously, points to the
most recently received active process block.) Activity
block isle initiates loop, Lucy steps comprise
blocks 1103 through 1117, that is exited only when it
returns a PER value of PULL. The first step in the loop,
Jo activity block 1103, subtracts 1 from the COUNT of the
process block pointed to by PER. Decision block 1104 then
; checks the value of COUNT to see if it is equal to or less
than zero. If it is not, then control action proceeds
through block 1109 (by passing blocks 1106 through 1116) to
activity block 1117, which changes PER to the address
stored in the LINT entry of the process block pointed to by
TAO or, in other words, the current process block. Control
then loops back to activity block 1103 as long as PER does
not have the value NULL. If the COUNT is less than or
equal to zero, then control proceeds through block 1105 to
decision block 1106. Decision block 1106 checks the value
; of STATUS in tile current process block. If STATUS is on,
control proceeds through block 110~ to activity block 1111.
If Strauss is of, control proceeds
., ,
~;2;29~35
through block 1107 to activity block lily.
Activity block 1111 takes the RUG value stored in
SO COLOR of the current process block and writes it into
the color map memory table entry indicated by the index
stored in the FROM Courier entry in that process block.
Control then passes to activity block 1112, which sets the
COUNT entry of the current process block to the contents of
the OFF TIME entry of that block.
Activity block 1116 then sets the STATUS of that
process block to OFF before control passes to activity
block 1117, whose action has been described previously.
Activity block 1110 copies the RUB value from the
color map entry indicated by the index stored in the FROM
COLOR entry of the current process block into the SAVE
COLOR entry of that process block. Activity! block 1113
then copies the RUB value from the color map entry
indicated by the index stored in the TO COLOR entry of the
current process block into the color map entry indicated by
the index stowed in the FROM COLOR entry of that process
block. Activity block 1114 then sets the COUNT entry to
the value stored in the ON entry. Finally Activity
block 1115 sets the STATUS entry to ON before control is
passed to Activity block 1117, whose action has been
described previously.
When the loop is finally exited, that is, when
PER returns the value NULL, the subroutine TICK is complete
and control returns to the main control program.
In the previous discussion, the assumption was
made that an active process list already had been
established.
FIG 12 is a flow diagram illustrating how one
active blink process is added to the active list Since
only one active process is allowed for the ordered pair of
FROM COLOR (FC~ and TO COLOR (TO), the current list of
active process blocks must be searched to determine if a
process is active for a given pair. This search is
indicated in box 1201. If the ordered pair (FC, TO is
, . .
I
-- 19 --
found in the currently active process blocks, that block is
made INACTIVE and is removed from the linked list as
indicated in box 120~ hen box 1205 is encountered, an
attempt is made to obtain a free process bloc from the
previously described FREE list. At decision box 1207 a
check is made to see if a free block was successfully
obtained. If no block was obtained the entire set of
possible blocks must have been already allocated to ACTIVE
processes and therefore no addition can be made, so the
entire process addition procedure is exited
If a free process block is obtained, it must be
initialized as illustrated in box 1210. The new process
always begins with a Stylus of OFF which guarantees that
the first transition will be OFF-to-ON as previously
stated.
The FROM COLOR, TO COrJOR and ON and OFF TIME's
are also initialized in box 1210 from data obtained from
the operand entered following the blink process opaqued
The phase delay (POD) is an offset from the next
OE~-to-GN transition ox the most recently received active
process (that is, the process of the head of the ACTIVE
process list). The head of the ACTIVE list is checked at
decision box 1211 in case the list is empty. If the list
is empty, then the phase delay does not apply and the
CURRENT COUNT in the new process block is set to the OFF
TIME as indicated in box 1219.
If an active process exists then two situations
arise, either the process is currently ON or OFF. The
STATUS of the process is checked in decision block 121~.
If the process is ON then tire next OFF-to ON transition
will occur when the CURRENT COUNT reaches the interval of
time represented by OFF TIME expires. Therefore, the total
time to the next OFF-to-ON transition will be the CURRENT
COUNT plus the OF TIME. In order to synchronize the new
process to the most recently received active process, its
Current COUNT is set to the lima until the next OFF-to-ON
transition plus any phase delay as shown in box 1210.
~2Z~
- 20 -
If the last active process has a STATS of OFF,
then the next Often transition will occur at a total
time equal to CURT COURT. The new process is therefore
synchronized to that transition simply by setting the new
process CURRENT COUNT to the CURRENT COUNT of the most
recently received process plus any indicated phase delay.
In all cases once the complete process block is
initialized, it is added to the active process list as
shown in BOX 12200 The ADD IT PROCESS returns control to
the main control program.
Referring to FIX. 13, exemplary color tables and
a timing diagram are illustrated for three active blink
processes. Successive representations of an eight entry
color table are illustrated in table 1301. Time is
indicated by time line 1312. A legend 1311 indicates the
assumed color valves of color table 1301. The information
that was used to establish the three blink processes is as
shown in Table 1.
~L2~29'~
TABLE 1
PROCESS 1
Arrival Time T = 0
FROM COLOR h
TO COLOR 3
ON TIME 2
OFF TIME 2
PEASE DELAY 3
PROCESS 2
Arrival Time T = 5
FROM COLOR 7
no COLOR
ON TIME 4
OFF TIME 2
PHASE DELAY
PROCESS 3
Arrival Time T = 10
FROM COLOR 3
TO COLOR 7
ON TIME 4
OFF TIME 5
PHASE DELAY
I
- I -
Tune color table 1301 at time To contains the
color value white in entry 1, the color value red in entry
3, the color value Green in entry and the color value
blue in entry 7. The other entries relay contain color
values but are not important in this example.
Process 1 arrives at time To and assuming no
active processes already exist, process 1 is activated with
a STATUS of OFF (1304). The phase delay that was specified
for process 1 is not relevant because no active blink
processes existed when the information for process 1
arrived at time To
then process 1 is activated the CURRENT COUNT is
set to the OFF TIME which it equal to 2 and therefore an
OFF-to-ON transition will occur at time To (1313).
When the OFF-to-ON transition occurs, the color
value in the color table indexed by the FROM COLOR, which
is equal to 7, is saved in the process block in the SAVE
COLOR entry 1302. The color value saved is blue shown by
the entry 1315. After the FROM COLOR is saved, the
contents of the color table indexed by the TO COLOR is
copied to the color table entry indexed by the FROM COLOR
This results in the color value red in entry 3 at 1316 to
be copied to entry 7 at 1317.
As a result of this change, any picture elements
which were previously displayed using the color value
stored in color map entry 7 will immediately change from
blue to red. The STATUS of process 1 will be set to ON and
the CURRENT COUNT will be set to the ON TIME which is equal
to 2. An ON-to-OFF transition will occur at time To
referenced by character 1314. At that transition the
previously saved color 1315 is restored in the color table
at the entry indexed by the FROM COLOR, which is equal to
7, and referenced by character 1318. The STATUS is again
set to OFF and the CURRENT COUNT is set to the OFF TIME
which is equal to 2. The above sequence is repeated as
long as the process is active.
Lo 33~;i
- 23 -
Process 2 arrives at time To which is after
process 1 has been activated. process 2 is started with a
STATUS of OFF and must be synchronized with the next OFF-
Tao transition of process 1. Since at tile To the
STATUS of process 1 is OFF then the time to the next OFF-
Tao transition will be equal to 1, which is the CURRENT
COUNT of process 1. A phase delay of 1 was specified with
process 2 so the OFF Title of process 2 is set to the sum of
the CURRENT COUNT of process 1 plus the phase delay of
process 2, which equals 2. This Setting results in the
first OFF-to-ON transition occurring at time To referenced
by character 1319. Process 2 then begins the color save,
copy and restore sequence previously described for process
1.
Process 3 arrives at title T=14 and must be
synchronized to process 2. The next OFF-to-ON transition
of process 2 occurs at time T=13, and, because of the phase
delay of 1, the first OFF-to-ON transition for process 3
will occur at time T=14, referenced by character 1321. As
with process 1 and 2, the save, copy and restore sequence
will continue for process 3 until changed by either another
specification for the same ordered pair of FROM COLOR and
TO COLOR or a general resetting procedure.
It should be noted that when colors are copied
from one entry in the color table to another that an
interaction between processes can result. This is
illustrated at time T=13 and T=14. At time T=13, process 2
makes an OFF-to-ON transition referenced by character 1320.
The color white is copied to color table entry 7 as
referenced by 1324. At time T=14, process 1 makes an OFF-
to-ON transition as referenced by 1322. At that
transition, the DAVE COLOR, referenced by 1325, is white
because of the previous copy operation performed by process
2 at time T=13. This interaction of colors between
processes is useful for simple animation and complex
blinking sequences.
~Z~3~
- I
FIG. 14 illustrates the state of the three
process blocks at time T=15~
