Note: Descriptions are shown in the official language in which they were submitted.
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COMMUNICATIONS SYSTEM HAVING RECEIVERS
WHICH CAN BE ADDRESSED IN SELECTED CLASSES
BACKGROUND OF THE INVENTION
This invention relates to a communications system for
transmission of audio and combined video, data and control
signals to remote receiving locations for retransmission under
the command of the control signals.
Transmission of audio and video signals to local
receiving stations for immediate use, rebroadcast or recordation
for later broadcast is well-established practice, particularly in
connection with distribution of television programming by various
television networks. Utilization of data to generate characters
which are displayed on a video screen over a single color
background or another video signal background is also established
practice. ~ ::
However, expansion in the availability of data of both
general and specific interest to various groups of data consumers
and the need for a system capable of efficiently transmitting
such data to specific remote locations and to control the further
broadcast, display or transmission of such data at those ~ .
locations have resulted in the need for audio, video and data :: :
transmission systems with associated control capabilities not -
previously available.
U.S. Patent No. 4,725,886 issued February 16, 1988 for
a Communications System havin~ an Addressable Receiver discloses
and claims communications systems utilizing a novel hardware and
software configuration simultaneously to transmit conventional
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video and audio program material together with data and control
commands within the constraints of conventional television signal
specifications to remote s~gnal processors or receivers within
the system which receive the entire transmission and process it
in a predetermined manner such that the data and the conventional
video and audio signals may be utilized at the remote receivers,
under network control, particularly for broadcast on local cable
television systems.
These systems transmit, typically utilizing a satellite
transponder, a first conventional video and audio television
signal together with a digital data stream transmitted in the
vertical blanking interval of the first video signal. The data
stream can also, of course, be transmitted by other methods, such
as using a subcarrier frequency. The data stream in the first
video signal comprises digital control and address data and
digital text data. A local receiver may process and retransmit
the first video (and audio) signal and, utilizing a character
generator, store the digital text data and process it into a
second ("satellite" text) video signal containing text for
transmission. In addition, the receiver may receive and
retransmit a third video (and audio) signal from a local source
such as a video recorder, so that local commercials or other
material may be displayed, and it provides a synchronization
signal which may be input to the local source to synchronize
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i-- 1 3 3 0 ~ 8 9
signals from it with other video signals processed or generated
by the receiver. So that local cable operators may also be able
to compose and display textual data, the receiver may also
receive digital data from a keyboard. This data, as well as data
from local weather sensors, is processed by the receiver into a
fourth video signal containing text. On command from network
control, the receiver may select for output the first satellite
video (and audio) signal, the third local video (and audio)
signal, or a solid color background video signal, and may combine
with any of these signals the ~econd (satellite) and/or fourth
local textual video signals.
The digital control and address data in the data stream
of the first video signal control the operating states~ or modes,
of such receivers and determine the video, audio and other
outputs of a particular receiver. Control data sent in the
"Output Mode Control Word" ("OMCW") of the data stream
determines, among other things, which video signals or
combinations thereof will be presented and which audio signals
will be presented, by controlling whether satellite video, local
video or character generator input will be processed and sent by
the receiver.
The address words of the data stream and the control
words following them allow each such receiver or a group of
receivers to accept, store and process particular text data and
to display this text in a particular format. Thus, different
-3-
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digital text data may be stored by different receivers in groups
of receivers for simultaneous presentation in response to the
OMCW contro`~ data which controls timing of such presentation.
Receivers such as those disclosed in U.S. Patent No.
4,725,886 may be utilized for a network of local affiliates
receiving transmissions from a single source dedicated to
television programming related to weather information and
advertising. Accordingly, the hierarchy of addressability
utilized in embodiments disclosed in that document contemplates
geographic organization of local receivers consistent with
weather patterns. That document emphasizes, however, that the
invention may also be adapted for transmission of entirely
different programming and data for other types of commercial
broadcasting and for non-commercial communications, including
teletext-only communications, and aspects of the invention may be
adapted to other uses such as various remote control networks.
A plurality of such receivers can be organized and
addressed hierarchically for purposes of receiving and processing
satellite video and teletext data according to a hierarchical
address structure of four sub-fields: Service, Zone, County, and
Unit. The address of a receiver is set by positioning switches
in the receiver. The receiver compares or matches sub-fields in
addresses of received data one sub-field at a time to determine
whether messages are addressed to it.
- 1 3 3 0 5 8 9 It has recently become useful, however, to arrange and
control classes of receivers not according to geographical
location or a hierarchical structure, but according to other
criteria such as, for instance, a certain market such as a
metropolitan area comprising portions of several counties or
zones. Advertisers appreciate this capability as well as viewers
who wish to receive the same information as others in their area
without discrimination according to geographic boundaries or
other hierarchical structures.
SUMMARY OF THE INVENTION
The present invention supplements the capabilities of
receivers such as those disclosed and claimed in U.S. Patent No.
4,725,886 by allowing receivers to be controlled according to
preselected classes independent of their hierarchical address
structures. This additional capability results from changes to
software in the receivers and the structure of data sent to them,
as disclosed more fully below.
Other additional capabilities according to the pre~ent
invention are the ability to cause receivers to enter to a "Crawl
Alert" mode or state with satellite video and audio and with a
solid color background in the bottom region of the screen across
which messages may crawl, accompanied by intermittent audio
signals.
The invention also allows receivers to display remotely
collected weather observations, such as those from local
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133~89
- 6 -
meteorological offices, if they sense loss of connection
with their corresponding temperature probes, and to
display crawl text corresponding to weather warning
information stored in RAM. The invention further allows
for the rainfall counter circuits to be easily reset or
updated from the receiver's keyboard.
Other aspects of this invention are as follows:
An addressable receiver for receiving video and
digital data signals, transmitting video output signals .
and controlling external devices, comprising, (a) means
for processing the video and digital data signals into a
first video signal available for receiver output, a
synchronization signal available for receiver output, and
a serial digital data stream for controlling the
receiver, (b) means for processing the digital data
stream to recognize within such stream control words, (c)
means for storing digital data contained in the digital
data stream, (d) means for recognizing within the digital
data stream hierarchical addresses, controlling the means :
for storing digital data selectively to store data in
accordance with the hierarchical address preceding such
data, and (e) means for recognizing within the digital
data stream non-hierarchical designator data, (f) means
for converting stored digital data into a second video
signal containing characters and available for receiver
output, and (g) means responsive to the digital data
. stream for controlling the receiver output.
An addressable receiver for receiving video and
digital data signals, transmitting video output signals
: and controlling external devices, comprising (a) means
for processing the video and digital data signals into a
first video signal available for receiver output, a
. synchronization signal available for receiver output and
a serial digital data stream for controlling the
receiver, (b) means for processing the digital data
stream to recognize within such stream control words, (c)
means for processing the digital data stream to recognize
within such stream hierarchical addresses and for storing
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digital data addressed to said receiver in accordance
with a hierarchical address contained in such data, (d)
means for processing the digital data stream to recognize
within such stream non-hierarchical designator data for
controlling operation of the receiver in accordance with
such data, (e) means for converting stored digital data
into a second video signal containing characters, which
signal is synchronized with the synchronization signal, ~ .
(f) means for receiving a third video signal, (g) means
for processing at least one of the control words into at
least one command signal, (h) means for receiving a
second data signal, (i) means for processing the second
data signal into a fourth video signal containing
characters, (j) means for combining the first or third
and either or both the second and fourth video signals
into an output-available signal, (k) means responsive to
the control words and the designator data for controlling
the receiver's output of the synchronization signal, the
command signal and the output-available signal, (l) means
responsive to a flag contained in the digital data for
overriding said transmitting means responsive to the
control words to cause the receiver to immediately to
alter its output signal, and (m) means responsive to
interruption of receipt of the signals for transmitting a
predetermined video output signal.
A communication system comprising a teletext~ ~:
transmitter and a plurality of addressable receivers
adapted to receive teletext transmissions from the
transmitter, and, responsive to hierarchical addresses
and non-hierarchical designator data contained in such
transmissions, process selected portions of such
transmissions, in which system the hierarchical addresses
define a plurality of hierarchical group levels in
~, 35 addition to the level comprising all the receivers and
the level comprising only one receiver, such that :-~
¦ receivers in subgroups of a hierarchical group level may
be addressed by addressing that group level.
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- 6b -
Other objects, features and advantages of the
invention will become apparent with reference to the
remainder of this document.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the data framing scheme -`
for a page header of a text page of data for transmission
in accordance with the preferred embodiment of the
present invention.
FIG. 2 is a diagram similar to FIG. 1 for any text
row 1-9.
FIG. 3 is a diagram similar to FIG. 1 for a
date/time row.
FIG. 4 is a diagram similar to FIG. 1 for a command
message to reset an ad hoc flag in receivers.
FIG. 5 is a diagram similar to FIG. 1 for a command
message to clear ad hoc flags in receivers.
FIG. 6 is a schematic diagram of bit values for ~:
switch settings for receivers according to the present
invention.
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FIG. 7 is a schematic diagram of bit values for switch
settings for receivers according to the invention of the parent
of this document.
FIG. 8 is a block diagram showing a receiver according
to the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
I Techniques of the present invention may be utilized
with receiver hardware such as that disclosed and claimed in U~S.
Patent No. 4,725,886.
Referring to FIG. 1, which shows page header line (or
row) framing in accordance with the present invention, the first
33 of the 37 bytes of that line remain the same as disclosed in
the parent of this document. The first two bytes are clock run-
in bytes and the third byte is a framing code byte. Byte 4 is a
row number byte which comprises a four-bit binary number having a
decimal range of 0 to 9. Zero identifies the row as a header and
a value of 1 to 9 identifies a line of text (see discussion of
text line below) and specifies its sequence in the page. Each
text page comprises ten lines or rows numbered 0 through 9. The
first line is a page header and each page is numbered. Page ;
number O is reserved so that a call for its display can be used
to indicate that no text is to be displayed.
Bytes 4-37 are all hamming code bytes, as are bytes 4
and 5 of the text line shown in FIG. 2, bytes 4-37 of the
date/time message line shown in FIG 3., and bytes 4-16 and 34-35
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133~89
of the set ad hoc market and clear ad hoc market lines shown in
FIGs. 4 and 5.
The page header (as well as the date/time message and
set ad hoc market) lines include in bytes 5-8 an "Output Mode
Control Word" (abbreviated "OMCW") which is the mechanism for
exercising real-time control over the "on-air" transmission of
receivers. The OMCW sub-fields containing data bits are, left to
right, as follows:
a. A "Local Program" one bit flag is used to select
the on-air audio and video source and to activate a
corresponding LED and solid state switches in the Logic
Output Section of the receiver. If the "Local Program"
bit is on (i.e., "1") and local video is present then:
1. local video is selected,
2. local audio is selected regardless of the
state of the Special Audio bit (described below),
3. the local program LED is turnéd on,
4. the local program solid state switch is
turned on, and
5. all character generator group output is
suppressed regardless of other indications in the
OMCW.
If the Local Program bit is off (i.e., "O", or local
video is not present, then:
1. satellite video is selected,
-8-
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~33~89
2. satellite audio is selected unless the
Special Audio bit is on,
3. the local program LED is turned off,
4. the local program solid state switch is
turned off, and
5. character generator group output is as
called for in the balance of the OMCW.
b. A "Local Pre-roll" one bit flag activates (0 = off;
1 = on) an isolated external control circuit which may be used to
cue-up a video recorder machine.
c. An "Auxiliary Audio" one bit flag selects the
auxiliary local audio input as the on-air source, over-riding the
audio source specified by the Local Program bit. It also
activates an isolated external control circuit which may be used
to control a local audio source and LED indicator. Thus, 0 =
Audio follows video, and 1 = Auxiliary Audio over-ride. ;~
d. An "Alarm" or "Weather Warning" one bit flag ~O = ~;
off; 1 = on) activates an electromechanical relay and an isolated
external control.
e. A "Radar" one bit flag is used in conjunction with
a Radar Enable switch and presence of local video input to select
the local video source and to activate a solid state switch which
may be used to turn on a video signal depicting a radar picture.
It never affects the on-air audio source. If the Radar bit is on
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(i.e., = 1), the local program bit is off, the Radar Enable
switch is on and local video is present then:
1. local video is selected,
2. the radar solid state switch is turned on, and
3. all character generator output is suppressed
regardless of other indications in the OMCW.
If any of the condition~ above are not met then the local program
bit prevails.
f. A "Region Separator" one bit flag (O = on; 1 = off)
acts as the separator attribute of the first text line of the
bottom text region.
g. A "Top Solid Background" one bit flag (O = title-
over; 1 = solid background) selects either title-over or solid
color background display of text in the upper text region.
h. A "Bottom Solid Background" one bit flag (O =
title-over; 1 = solid background) selects either title-over or
solid color background display of text in the lower text region.
i. A "Top Text Page" six-bit binary number specifies
the page to be displayed in the upper text region. Page number
"O" is a pseudo-page of zero lines.
j. A "Bottom Text Page" two-bit binary number
specifies the text to be displayed in the bottom text region.
Bottom Text Page = 0 is a pseudo-page of zero lines, = 1 means
display date/time and weather instruments readings, = 2 means
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display local crawl and = 3 means display alternate crawl from
text page 51 (weather warning information).
Bytes 9 and 10 are the "Page Number," an eight bit
binary page number in the range 0 to the maximum number of pages.
Page 0, Row 0, as stated above, is utilized as a date/time
record. Page numbers greater than or equal to 128 are reserved
for non-text messages. Page numbers 254 and 255 are currently
implemented instances of such messages and are described below. ~ ~
The "Address" field, bytes 11-16, comprising twenty- ~ ~ 0
four data bits (in addition to twenty-four Hamming Code Bits)
allows a plurality of receivers to be organized and addressed
hierarchically for purposes of receiving and processing satellite
video and teletext data. Thus, certain teletext messages may be
addressed only to, and stored and processed only by, a particular
receiver (a "Unit") or a group or groups of receivers ("County,"
"Zone" and "Service"). In accordance with this ability, the
address is a hierarchical structure of four sub-fields which are,
left to right: "Service" (3 bits), "Zone" (10 bits,), "County"
(5 bits), and "Unit" (6 bits). The address of each receiver may
consist of Service 001 or another service number stored in ROM
and twenty-one bits, representing the remaining sub-field values,
set into receiver switches in the Switch Input Section of the
receiver. Address matching proceeds one sub-field at a time,
from left to right. If a received sub-field contains a value of
zero, that sub-field and all succeeding sub-fields are considered
--11--
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to match the corresponding sub-fields of the receiver without
further comparison. Thus, for instance, an address containing a
value of zero for "County" would match all receivers having the
"Zone" of that address.
Byte 17 is the "Line Count," a four bit binary number
in the range 0 to 9 establishing the line count attribute for
display and the highest row number to be received in the current
page.
Bytes 18 and 19 are "Page Attributes," a collection of
one bit display attributes and one bit mode change commands.
These mode change commands provide the only mechanism for forcing
a change in operating mode on an addressable basis, since in the
NORMAL mode (described below) the OMCW is processed independent -~
of the destination address of the rest of the message. The eight
Page Attribute bits are utilized, reading left to right, in the
described embodiment as follows:
a. An "Unused" bit is reserved for future use.
b. A "Freeze" bit forces a transition into FREEZE
mode.
c. A "Weather Advisory" bit forces a transition into
ADVISORY mode.
d. A "Weather Warning" bit forces a transition into
WARNING mode.
e. An "Unused" bit is reserved for future use.
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f. A "Flip'l bit indicates that the display of any
chained pages will be accomplished by successive display of one
page at a time. ~f
g. A "Roll" bit indicates that the display of any
chained pages will be accomplished by continuous text roll.
h. A "Chain bit indicates that the next higher
numbered page is logically attached to this page.
"Line attributes" occupy eight successive fields of two
bytes each, bytes 20-33. Bytes 36 and 37 are line attributes for
both lines 8 and 9 of a page of text. Each two-byte field 20-33
contains display attributes for its corresponding text line.
Left to right, these are:
a. A "Separator" bit that indicates the display of a
solid separator bar above the corresponding line of text.
b. A "Flash" bit that indicates that the text will
flash off and on.
c. A "Re~erse" bit that indicates that any text or
separator will appear in black rather than white and that the
character borders, if present, will be white rather than black.
d. A i'Border" bit that indicates a contrast border
around the edges of the characters.
e. A four bit "Color" code that indicates the
background color assoc~ated with the line.
Bytes 36 and 37 control display attributes for both
lines 8 and 9 of text.
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As shown in FIGs. 1 and 2-5, Bytes 34 and 35, which
were previously occupied by line 8 display attributes, form an
OMCW Extension. Each byte comprises four data bits and four
hamming code bits. The OMCW Extension forms the low order
portion of the Extended OMCW. The OMCW Extension is defined as
follows, reading left to right:
A. Three unused bits.
B. Five "market" bits.
The remaining bits are four hamming code bits located to the left
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of the data bits in each byte.
The text line of FIG. 2 may be the same as that
disclosed in FIG. 41 of the parent document. The first five
bytes are two clock run-in bytes, a framing code byte, a row
number byte, and a height/width byte. The remainder of the bytes
correspond to characters of text.
Referring to FIG. 3, the date/time message line (row 0,
page O) utilizes the framing described for a page header for its
first ten bytes. Byte 11 is the "time zone" indicating the time
zone that the accompanying date and time apply to, utilizing a
three-bit code designating time zone and whether daylight savings
time is to be used. The setting of three corresponding switches
in the receiver provide the receiver with the ability to process
only matching date/time messages. Byte 12 is the day of the
week; byte 13 is the month of the year; and bytes 14 and 15 are
the day of the month. Byte 16 is the hour of the day; bytes 17
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33058~ ~ i
and 18 are the minute; bytes 19 and 20 are the seconds; and byte
21 communicates a.m. or p.m.
Bytes 22-31 may be used for alternative date and time
information in a format similar to bytes 12-21. The setting of a
switch in the receiver determines which of the two groups of date
and time information will be processed. A check sum byte field
occupies bytes 32 and 33. It contains the low-order eight bits
of the arithmetic sum of the four-bit de-hammed data portions of
the 21 bytes, beginning with the byte ~ollowing the page number
and ending with the byte preceding the check sum. Bytes 34 and
35 contain the OMCW Extension and bytes 36 and 37 are unused.
Bytes 1-10 and 34 and 35 of the set ad hoc market and
clear ad hoc market lines as shown in FIGs. 4 and 5 are the same
as those in the page header and date/time message line. The
other bytes in these lines are unused.
Text page headers may have a page number between 1 and
127. Thus, using 8-bit two's compliment arithmetic the page
number is non-zero and non-negative. The page number 255 in a
row 0 is a set ad hoc market line which sets the ad hoc flag in
receivers to which it is addressed, while page number 254 in a
row 0 is a clear ad hoc market line which clears the ad hoc flag
in receivers to which it is addressed.
As shown a comparison of in FIGs. 6 and 7, the switches
in receivers can be redesignated to accommodate these new data
lines. The right-most 24 switches corresponding to time zone,
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zone, county and unit, respectively, remain the same. In the
other 8 switches, the left-most 4 switches correspond to the
"market~ mentioned above in connection with the Extended OMCW.
The 5th switch is a radar enable switch, the 6th switch is a
spare, the 7th switch is the fifth (low order) live local market
switch, and the 8th switch is the alternate time zone.
Non-hierarchical classes of receivers may be controlled
in two ways in accordan~e with this format. First, they can be
addressed when their combination of market switch settings match
the market bits contained in the OMCW Extension of data lines.
Second, they can be addressed by addressing individual or groups
of receivers and sending set ad hoc market lines to the addressed
receivers. A value in the range of 1 to 30 for the five market
bits is used to address desired receivers with corresponding
market bit switch settings. A market bit value of 31 in the OMCW
Extension specifies the current class of receivers in which the
ad hoc market flags are set.
The system control or teletext program, written in
Intel 8085 Macro Assembly Language, is assembled and the
resulting machine code stored in a ROM chip for inclusion in
receiver 110. The complete assembly listing appears below. The
main body of this program, which i~ entered as a result of a CPU
hardware reset, performs certain system initialization functions ~ -~
and then repeatedly executes a loop consisting of various
housekeeping chores. The balance of the program consists of
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13305~9
interrupt service routines that are invoked by hardware
interruptS, which occur asynchronously with respect to execution ;~
of the main program body, and by software RST instructions.
I
Main Proqram Body
Entry to this routine is through the 8085A reset vector
address. The program begins system initialization by setting the
stack pointer to the base address of the stack. Next, the alarm
relay and all of the solid state switches are turned off and the
satellite video signal is selected. Then the front panel LEDs
are turned off and a delay loop of approximately two seconds'
duration is entered to allow the rest of the receiver hardware to
stabilize. The 32 switch inputs are then read and saved and all
maskable interrupts are disabled.
A group of software controlled timers are then zeroed.
All of these timers will subsequently be counted in half-second
intervals. Since no half-second clock exists in the system, one
is simulated using the TRAP interrupt which occurs at NTSC
television vertical frequency (59.94 Hz) and a software counter
that is initialized here for 30 counts.
Next a group of flags is initialized. Then a buffer ~ ~-
that is used to format weather sensor readings is initialized and
the first sensor input values are read and placed in the buffer.
The USART control registers are then initialized to enable serial ;~
data communications. The program then performs set-up of the DMA
-17-
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1 3 3 0 5 8 9 r ~t~
Controller for subsequent teletext data storage. A value
corresponding to a received double bit error is placed into the
row number field of each line of the four-line teletext data
buffer in memory. This insures that the contents of a line
buffer will later be discarded by the program if no teletext data
is received in the corresponding line of the satellite video
signal.
Initialization continues with the sending of a
reset message across the inter-processor link to the character
generator control processor. Finally, the necessary actions are
taken to establish NOSAT mode.
The main program then enters a loop where it will
remain as long as the receiver continues in operation. In this ; -
loop the software timer for the audio beeper is checked. If it
is active and its maximum count has been reached, the beeper is
turned off. The 32 switch inputs are then read. A software
controlled weather sensor timer is checked, and if it has expired
the local weather sensors are read. If the temperature sensor
reading is at its extreme over-range value, indicating that a ;
short circuit jumper has been installed across the temperature
sensor input terminals, a special sensor message is formatted to
inform the Character Generator Controller processor that the
contents of text page 50 is to be used in lieu of actual sensor
readings. Otherwise, a sensor message containing the actual
readings is formatted. In either case a flag is set to indicate
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133~58~
that the sensor message is ready for transmission to the
Character Generator Controller processor. Control is then
returned to the beginning of the loop.
RST1 Routine
This software invoked routine saves the status of all -
of the 8085A registers on the stack.
RST2 Routine
This software invoked routine restores the previously
saved status of the 8085A registers from the stack.
' ''
RST3 Routine
Unused.
RST4 Routine
Unused.
TRAP Routi,ne
This is a hardware interrupt service routine. It is
entered at the beginning of each vertical sync pulse (VDRIVE)
from the Gen Lock Section. For proper system operation, the
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execution time of this routine must be short enough that it will
be completed before the occurrence of the RST5.5 interrupt caused
--19-- :
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by the sync pulse of video line 18. This routine must therefore
complete in less than 1.08 milliseconds.
This routine first saves the processor state. Since
the 8085A TRAP interrupt cannot be masked, a check is made to see
if the main program is still performing initialization. If so,
the processor state is restored and this routine is exited.
Otherwise the routine continues.
All timers that use 1/60 second counts are incremented.
If the 1/2 second interval counter has expired, it is reset and
all of the timers that use 1/2 second counts are incremented. ;
The satellite video present detector is read. If satellite video
is not present and the system is not in NOSAT mode, WARNING MODE
or ADVISORY mode, then NOSAT mode is established. If satellite ~ ~
video is not present and the system is already in NOSAT mode, the -
three hour timer is checked. If it has expired, a reset message
is sent to the Character Generator Control processor to cause
reinitialization of all stored text pages.
If video is present and the system is in NOSAT mode,
the video present software timer is checked. If video has been
present for one second, then NOSAT mode is exited and NOCTL mode
is established.
If video is present and the system is in WARNING mode
or ADVISORY mode, the two minute software warning and advisory
timer is checked. If it has expired, the current mode is exited
and NOCTL mode is established.
.
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If video is present and the system is in NORMAL mode,
the good OMCW software timer is checked to determine if a full
second has elapsed without receiving a valid OMCW. If it has,
then NORMAL mode is exited and NOCTL mode is established.
In all cases, this routine concludes by checking a five
second software timer to determine if it is time to send sensor
readings to the Character Generator Control processor. If so, it
sets a flag and resets the timer. Finally the processor state is
restored and the TRAP routine is exited.
RST5 Routine
Unused.
RST5.5 Routine
This is a hardware interrupt service routine. It is
entered at the beginning of the horizontal sync pulse for video
line 18 as indicated by the signal WEN. It is this routine that
processes received teletext data. Its execution must be
completed before the next TRAP occurs. Execution must therefore
not require more than 15.6 milliseconds.
This routine first saves the state of the processor on
the stack and resets the signal that invoked it. It then checks
to see if local video is present and sets an LED to so indicate.
If local video is not present a check is made to determine if
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local video is currently selected. If so, it is deselected,
satellite video is selected and the remaining functions of the
current OMCW are appropriately activated.
A processing loop is then entered which will be
executed four times, once for each of the four teletext data
lines contained in the current video field. The ROW NUMBER field
is de-hammed by table look-up. If the ROW NUMBER contains a
double bit error then a flush flag is set so that the balance of
the current message will be ignored and no further processing of
this line is performed.
":
If the row number is zero then the OMCW, the OMCW
EXTENSION, the ADDRESS and the PAGE NUMBER are de-hammed and
packed. If the PAGE NUMBER contains a double bit error the flush
flag is set and no further processing of this line is performed. -
If the PAGE NUMBER is zero, then this line is a DATE/TINE message
and it is processed accordingly and, depending upon the ALTERNATE
TIME ZONE switch of the switch inputs either the primary or the
alternate date and time field, is sent to the Character Generator
Control processor if its TIME ZONE field matches the code in the
corresponding three switches of the switch inputs. Processing of
a DATE/TIME message then continues with the OMCW field as
described below.
If the ROW NUMBER is zero, the OMCW and the OMCW
EXTENSION, together referred to as the EXTENDED OMCW, are now
processed. If they are error free and match the last received
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EXTENDED OMCW then the current system mode is checked. If the
system is in NORMAL mode, then the MARKET field of the OMCW -
EXTENSION is checked. If it is non-zero and either it is less
than 31 and it matches the value set in the five MARKET switches
of the switch inputs or it is equal to 31 and the internal AD HOC
flag is currently set then the current OMCW is set to 2000-hex
and the remainder of the received OMCW is ignored. This causes
the auxiliary audio channel to be selected for retransmission
along with satellite video. By supplying the auxiliary audio
input from an additional audio channel transmitted to the cable
system via satellite this makes possible the retransmission of
customized live audio and video programming by receivers in the ;~
selected market while receivers in other markets retransmit text
over a solid background accompanied by the first audio signal
under the control of the remainder of the OMCW.
If the MARKET field conditions above are not met then
the two minute Crawl Alert count-down timer is examined. If that
timer is non-zero, indicating that a Crawl Alert is in effect,
then the BOTTOM TEXT PAGE field of the new OMCW is forced to a
value of three and the BOTTOM SOLID BACKGROUND bit in the new
OMCW is forced on. Finally the new OMCW is saved as the current
OMCW and all of the conditions it now specifies are established.
If the system is in NOCTL mode and the newly received OMCW value
has both its LOCAL PROGRAM and LOCAL PREROLL bits off then NOCTL
mode is exited, NORMAL mode is established, the new OMCW is saved
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~` 1330589 -; -
as the current OMCW and the conditions it specifies are
established. ;~
It is important to note that this OMCW processing
occurs regardless of the contents of the ADDRESS field, and thus -~
provides simultaneous real-time control of all of the receivers -~
110 in a network.
Processing of a line with ROW equal zero and PAGE not
equal zero continues with the already de-hammed ADDRESS field.
If this field contains any double bit errors then the flush flag ~
is set and the balance of the line is not processed. Otherwise, ~;
hierarchical address checking is performed. This is done by left
to right processing of the subfields SERVICE, ZONE, COUNTY and ~-
UNIT. For each subfield of the message address, the subfield is
tested for a value of zero. If it is not zero it is compared to
the corresponding subfield of the receiver's address. If the
message subfield is either zero or equal to this receiver's value
then the subfield is considered to be "matched." If all
subfields are "matched" then the message is for this receiver, so
the flush flag is turned off, the "Unit Addressed" LED is turned
on and processing of the balance of this line and of any ensuing
lines of this message will be performed. If any subfield fails
to be "matched" then the flush flag is turned on, the "Unit
Addressed" LED is turned off and the balance of this line is not
processed further.
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~. .
If the message is addressed to this receiver and the
PAGE NUMBER is 255 then the internal AD HOC flag is set and
processing of this message is complete. `
If the message is addressed to this receiver and the
PAGE NUMBER is 254 then the internal AD HOC flag is cleared and
processing of this message is complete.
If the message is addressed to this receiver and the
PAGE NUMBER is greater than zero but less than 128 then this is a
Page Header for a text page, and the balance of the line is de-
hammed and used to create a page header message which is sent tothe Character Generator Control processor. The saved row number
is set to zero, and the processing of the line is completed.
If the received line has a non-zero ROW NUMBER the
flush flag is tested. If it is on then no further processing of
this line is performed. If it is off and the received ROW NUMBER
is not greater than the previously saved row number then the
flush flag is turned on and no further processing of this line
will be performed. I~ the flush flag is off and the ROW NUMBER
is greater than the previously saved row number then the new ROW
NUMBER value becomes the saved value and the line is processed.
This is done by de-hamming the HEIGHT/WIDTH field and then
sending the line to the Character Generator Control processor.
For all of the previously mentioned conditions, if the
flush flag is on or is turned on then the received line does not
have to be sent to the Character Generator Control processor.
~ .
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~ 1330589 ~ ~
This creates an available period of time that is used to send a -~
sensor message to the Character Generator Control processor if
the main program has set the sensor message ready flag. Whenever
a sensor message is sent, the ready flag is cleared.
After processing all four teletext lines in the above
processing loop, this interrupt service routine performs the
necessary initialization for the next DMA operation, restores the
processor status from the stack and exits.
RST6 Routine
Unused.
RST6.5 Routine
This is a hardware interrupt service routine which is
entered whenever the USART in the Serial Data Communications
section completes the sending or receiving of a character.
RST7 Routine
Unused. ;
RST7.5 Routine
This hardware interrupt service routine is entered as
the result of the Character Generator Control processor
acknowledging receipt of a transfer of data across the
interprocessor link. The RST7.5 in`errupt is in fact masked at
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'.'~
133~8~ ~ ~
all times so that the routine is never actually entered.
Instead, the RST7.5 interrupt pending status is used as a flag to
synchronize transmission to the Character Generator Control
processor.
CRAWL ALERT STATE
The present invention also allows for receivers to
display messages that crawl across the bottom of the screen while
satellite video appears on the upper portion. The previously
unused bit in the page attributes field of the page header line
is redefined as the crawl alert bit. Receivers may enter the
crawl alert state upon receipt and storage of the last line of a
text page that has the crawl alert bit on in the page attributes
field of its header.
Upon entry into the crawl alert state, the "Bottom
Solid Background" flag is set to 1 and the "Bottom Text Page" is
set to 3 in the active OMCW and in all subsequently received
OMCW's for 2 minutes. This provides for alternate crawl display
on a solid color background in the bottom region of television
screens controlled by the receiver while maintaining video on the
rest of the screen along with audio in accordance with the
current OMCW and subsequently received OMCW's. An intermittent
audio signal will be added to the audio output, mixed over the
program audio, the total duration of which is approximately five
to six seconds.
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:. ... . . . . . . .. .
133~89
If satellite video is lost for 45 consecutive video
fields while in crawl alert mode, the active OMCW is forced to ; ~ ;~
2707-hex and the crawl alert mode will continue to normal
conclusion.
ALTERNATE SENSOR DATA
If a receiver detects that its corresponding ;
temperature probe is not connected, then instead of suppressing
the display of all sensors, the lines of page 50 (remotely
collected weather observations such as those from local
meteorological offices) will be displayed one by one beneath the
date/time line on screens for televisions controlled by the
receiver. The lîne count field in row O of page 50 will be used
to establish the last line to be displayed before returning to
the first line. If text from page 50 is being displayed in lieu
of sensor data and the bottom solid background bit in the OMCW is
on, the background color for the entire bottom text region and
the bottom safe region will be taken from the color attribute for
line 1 of page 50. If, on the other hand, the line count in page
50 is 0, then a blank line will be displayed and the color will
be set to blue (color 5).
ALTERNATE CRAWL
¦ A value of 3 in the Bottom Text Field in the OMCW may
be defined as the Alternate Crawl bit. When this value occurs,
I the on-screen display will be the same as for the Local Crawl
1 25 with only the following three exceptions. First, the text will
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be from RAM text page 51 (weather warning information). Second,
the background color associated with the bottom text region and
the bottom safe region is the line 1 color attribute from page
51. Third, the number of characters in the message is taken to
be 32 times the line count attribute of the page.
The foregoing is provided for purposes of explanation
and illustration. Modification and enhancements to the
embodiment disclosed in this document may be made without
departing from the scope and spirit of the invention.
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