Television Video Pattern Generator System

This invention relates generally to television signal generators, and more particularly to multiple scan rate video test pattern generators for raster scan display devices such as television sets.

Modern television applications are demanding ever greater accuracy in cathode ray tube (CRT) displays. Computer generated images are developed with great timing accuracy and data analysis has been carried to the point that systems are offered in which measurements can be made directly off the television image. Accuracy of placement is paramount in such applications as computerized medical x-ray, industrial process control, etc. This has placed stringent demands on the stability and scan accuracy of television display devices. The response to these demands has been development of more precise television display devices which in turn has led to the need for more precise test techniques and equipment to evaluate a more demanding level of performance.

Television test pattern generators are used to generate a variety of video test patterns which are used to permit adjustment of television receivers or which may be used in the manufacturing and service of television receivers and television signal transmitting equipment.

Examples of test pattern generator systems are disclosed in U.S. Pat. Nos. 4,149,178; 4,093,960; 3,917,902; 3,879,749; 3,019,289; and 4,417,275.

Conventional television test pattern generators require composite, horizontal and vertical blanking, horizontal and vertical drive inputs and provide a composite video signal output.

The television raster is scanned in horizontal lines which progress from the top of the raster to the bottom of the raster. PG,3 After a total raster field has been scanned the process is repeated. In many applications two fields are scanned to complete one "frame" and the fields are "interlaced".

The composite video signal for scanning the television raster is comprised of both picture and synchronizing information. The raster scan synchronizing information consists of horizontal and vertical scan pulses of precisely determined widths and timing. The scan rate can be described on either a time basis or a pixel basis. A pixel is defined as a discreet bit of information corresponding to a discreet picture element.

H drive is a pulse train in which a pulse starts at the end of every television scanning line, its function being to mark the time interval between the end of one line and the start of another line. The H drive pulses may be used to control the horizontal deflection "flyback" and other signal processing. The horizontal drive pulse train is continuous and uninterrupted even during the vertical synchronizing interval. V drive is a pulse train in which a pulse starts at the end of each television field, its function being to mark the time interval between the end of one television field and the next. The V drive pulses may be used to control the vertical deflection "flyback" and other signal processing.

Blanking is a mixture of horizontal and vertical information used to control the "blackout" of a television screen during deflection return or "flyback" between horizontal lines and vertical fields. The blanking pulses are wider than drive and sync pulses in order to insure that all transitions are invisible, i.e. blanked.

Sync is a complex combination of the horizontal and vertical pulse information used to control the decoding of a television signal by the display device, recorder or other type of video processing equipment. Sync is usually mixed with the video information to produce a composite picture signal.

The scan rate is determined by the number of scan lines per field and desired field repetition rate. Most television systems are "interlaced" to avoid a visible flicker in the display, usually at a 2:1 ratio; 2:1, interlaced ratio means that two entire display "fields" must be developed to generate one complete "frame" or image. In the United States, field and frame rates are 60 HZ and 30 HZ respectively, whereas in countries having 50 HZ power, including the European Countries and Japan the field and frame rates are 50 HZ and 25 HZ respectively. Television operation without interlacing, commonly referred to as 1:1 interlace, is also fairly common.

Recently and particularly in the interface of television equipment with computers, there has been a new proliferation of scan rates. There is the never ending search for means to pack more information into a given area at the expense of inactive (blanking) time.

The different types of television systems, e.g. domestic broadcast, foreign broadcast, industrial and military, operate at many different scanning rates. Complete specification of a scan rate requires careful and precise definition of the scan parameters such as the horizontal scanning line repetition rate [usually expressed in kHZ], the number of scanning lines to be developed in each television field, the number of television fields which make up a complete frame, and the widths of the pulses present within the various synchronizing wave forms.

The format of H drive, V drive and blanking is the same for all scanning rates. However, the sync wave form can occur in any one of three formats, namely broadcast, industrial and military. In the broadcast system the vertical sync pulse interval is preceded by a front porch interval and followed by a back porch interval each porch interval having a duration of three scanning line intervals. Six 2H rate equalizing pulses are superimposed on the sync signal during the front porch and back porch intervals, i.e. six equalizing pulses during each such interval, and six 2H rate serration pulses are superimposed on the vertical sync pulse. Domestic broadcast sync also includes horizontal front porch intervals preceding the horizontal sync pulses.

The sync for industrial television is the same as for broadcast television except for the omission of the equalizing pulses and serration pulses. The sync for military television does not include equalizing and serration pulses, has no horizontal front porch, and no horizontal rate pulse information during the vertical front porch interval of three scanning lines.

Conventional sync generator circuits for test pattern generators have been limited in their applicability to test various types of television systems. Typically they provide only one scanning rate depending upon the type of television system with which the test pattern generator is to be used. It is therefore desirable to provide a selectable rate sync generator for universal application to various types of television systems whereby the scanning rate may be selected over a wide range of specifications.

In one prior art patent, U.S. Pat. No. 4,417,275, assigned to the assignee of record of the present application and which is incorporated herein by reference, a selectable rate sync generator system is provided which selects the desired scan rate by specifying the total horizontal line time and the number of scan lines which are to occur in two fields, regardless of the number of fields which make up a frame. The horizontal repetition rate is either specified or can be calculated. The calculated horizontal line time is selected by a total horizontal line time thumb wheel selection switch which results in the desired horizontal rate. Another thumb wheel selection switch in the system is set for the desired number of scan lines in two fields.

Signal source 1206A, which is a pattern generator and sync generator manufactured by Visual Information Institute, Inc., the assignee of the present application, utilizes a plurality of switches to set various parameters for generation of the synchronizing waveform and pattern. This device and the accompanying technical manual therefor is incorporated herein by references.

A problem with the prior art sync generator test systems has been that, in pixel based rasters, the number of horizontal lines per field and the line time needed to be calculated. This process was time consuming and unwieldy. Furthermore, in such systems the oscillator frequency had to be varied to accomodate the different system requirements, whereby an infinitely variable oscillator had to be provided. This requirement placed special demands on the system designer. It is therefore desired to provide a sync generator for producing variable scan rates with a fixed frequency oscillator.

While the raster scan test pattern generator described in the above-identified prior art U.S. Pat. No. 4,417,275 is satisfactory for many applications, it is desirable to provide a test pattern generator which is readily applicable to television systems wherein the rasters are defined in pixels or number of data bits per horizontal line without the need for multiple calculations in the use of the generator.

One prior art pixel based sync generator system has been provided wherein a frequency synthesizer is used comprising a variable oscillator having a variable frequency. The system requires entry of a few major parameters defining a scan rate and then calculates all values for the desired scan rate. The disadvantage of the system is that binary integers must be used for computing the different frequencies, whereby certain frequencies cannot be provided with the system and certain raster specifications will not be achievable. Additionally, the lack of sufficiently fine resolution achieved with that system at the higher frequency ranges of the oscillator is undesirable.

What is therefore desired is to provide a universal time based sync generator system wherein multiple scan rate test patterns, both time and pixel based, can be generated by entering the parameters for all the horizontal and vertical sync pulse elements into a keyboard and wherein the system builds or generates the scan rate from the discrete defined sync elements.

Another disadvantage of the above-identified prior art pixel based sync generator system is that all entries must be made on the keyboard or keypad. Thus with that system, if a television unit were being tested and several different patterns were desired to be viewed, such as a bar pattern, a dot pattern, gray scale, etc., this could not be quickly achieved as new entries would have to be made in the keyboard. What is therefore desired is a sync generator system wherein the parameters for a particular scan rate are preset in a keyboard and wherein a control is provided which permits rapid selection of different types of test patterns which are generated utilizing the scan rate parameters keyed into the keyboard.

What is also desired is a sync generator wherein stored raster scan test patterns can be altered and customized as desired.

What is furthermore desired is a sync generator wherein stored raster scan test patterns can only be altered by entering a software security code into the keyboard.

What is still further desired is a test pattern generator which provides a default scan rate when the system is first turned on, whereby a predetermined raster scan rate is provided to prevent any damage to the Cathode Ray Tube unit being tested.

What is yet further desired is a sync generator system having a keyboard display for displaying parameters and other items in a user friendly readable language rather than digital code.

The present invention overcomes the disadvantages of the above prior art test generators by providing an improved test generator which is applicable to a wide variety of television systems, both time based and pixel based. In this system parameters and timing are indicated on an alpha-numeric display. The operator may generate or build a custom rate, one element at a time according to parameters entered on a keyboard or may choose standard scan rate proportions whereby a rate will be computed automatically. Thus it is possible to synthesize a scan rate from the individual pulse elements whose parameters are entered into the keyboard. Rates may be stored, recalled for use, edited, or deleted, by keypad code entries. Memory storage is provided for a large number of raster structures. Software lockout is provided to prevent unauthorized editing without a proper access code.

A sync generator system has been developed by the assignee of record of the present invention whereby a proportional standard is provided which is applicable to all scan rates. This system overcomes the problems inherent in previous systems and is convenient for clocked generation of sync signals by modern digital techniques. Thus this system provides a totally clocked system for automatically calculating a scan rate in which all pulse widths are expressed as percentage of total horizontal line time. The format is therefore called a proportional format.

In order to simplify equipment and calibration procedures and thereby to minimize equipment costs the instant invention provides a universal format for horizontal scan rate raster development based on a 0.1 microsecond timing increment. In the system according to the invention all horizontal rate parameters e.g. total H line, H blanking width, H front porch etc., are defined to the nearest 0.1 microsecond and are programmed into a keypad. Increments of time smaller than 0.1 microseconds are rounded off. Vertical parameters are established in increments of half lines. Pulses such as V blanking, V drive, V front porch, and V sync are configured to the nearest half-line.

Thus in the system according to the present invention the operator can either use a preset or proportional format wherein the entire scan rate is calculated automatically or the operator can synthesize or build a custom raster rate from pulse increments.

Furthermore, a selection control is provided in addition to the keypad for rapidly selecting test patterns without the need for entering a code into the keypad.

Another advantage of the present invention is the ability to edit and customize raster scan rates as desired.

Yet a further advantage of the present invention is that a pattern generator is provided whereby patterns can be generated by selecting the desired pattern with a separate pattern selection control.

It is a still further advantage of the present invention that stored or memorized raster scan rates may only be altered by entering a software security code into the keyboard.

It is yet a further advantage of the present invention that the system provides a default scan rate when the system is first turned on, thereby preventing damage to the cathode ray tube unit being tested.

Yet another advantage of the present invention is that the keyboard display can be read by the the operator without resorting to a decoding chart.

The invention, in one form thereof, comprises a selectable rate sync generator for a video test pattern generator. The selectable rates sync generator comprises a keyboard for selecting individual and independent raster scan signal pulse width and timing parameters for the horizontal and vertical synchronizing waveforms for a raster scan. The sync generator further comprises means coupled to the keyboard means for generating a time based raster scan signal by building the desired scan signal from individual pulse elements having the selected width and timing parameters.

The invention, in one form thereof, further provides a video pattern generator comprising a keyboard means for individually entering data values representing the incremental pulse width and timing parameters for all the scan rate pulses comprising a raster scan structure. A sync generator means is provided coupled to the keyboard means for generating a time based scan rate composed of pulse elements having the selected pulse widths and timing values. A fixed frequency clock is coupled to the sync generator means for controlling the sync generator and a raster pattern selecting means is provided for selecting a desired raster pattern. A pattern generator means is provided coupled to the sync generator means and the raster pattern selecting means for generating a selected raster pattern at the generated scan rate.

The present invention, in one form thereof, still further provides a video test pattern generator including a fixed frequency master clock and a keyboard for selecting scan rate elements by individually entering data values representing the pulse widths of the pulse elements comprising a scan raster. A readout means is provided coupled to the keyboard means for displaying selected scan rate data. Selecting means is provided for selecting a raster scan display pattern sync generator means is provided coupled to the keyboard means and the clock means for generating a time based scan rate comprised of the selected pulse elements. Pattern generator means is provided coupled to the sync generator means and the selecting means for generating a selected test pattern at the generated scan rate.

The invention, in one form thereof, comprises a method of generating a raster scan signal comprising entering individual pulse widths and timing parameters into a selecting means, storing said parameters in a memory, and generating a scan signal by building a scan signal comprised of pulses having the selected individual widths and timing parameters.

An object of the present invention is to provide a video test pattern generator wherein a customized raster scan rate can be provided including individual elemental pulses whose width and timing are individually specified by the operator.

Yet another object of the present invention is to provide a television video pattern generator wherein the raster scan rate can be edited and customized as desired.

Another object of the present invention is to provide a television video pattern generator system wherein raster scan rates may be stored and memorized and may only be altered by entering a software security code into the keyboard.

A still further object of the present invention is to provide a television video pattern generator which provide a default scan rate when the system is first turned on to prevent damage to the cathode rate tube being tested.

Yet another object of the present invention to provide a video test pattern generator wherein the keyboard display can be read by the operator without resorting to a decoding chart.

A yet further object of the present invention is to provide a video test pattern generator wherein a scan rate can be automatically calculated and wherein the pulse elements comprising the scan rate are expressed as a fixed percentage of total horizontal line time.

Still a further object of the present invention is to provide a video test pattern generator having a fixed frequency master oscillator.

The above mentioned and other features and objects of this invention and the manner of obtaining them will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1A is a simplified schematic block diagram of the apparatus;

FIG. 1B is a simplified schematic block diagram of the pattern generator input circuitry;

FIG. 2A is an elevational view of the control panel;

FIG. 2B is a schematic diagram of the pattern generator function switches including the resolution repetition rate switch and the pattern function select switch;

FIG. 3 is a simplified schematic block diagram of the central processing unit and program memory;

FIG. 4 is a block diagram of the data acknowledge generator;

FIG. 5 is a block diagram of the microprocessor and associated buffers;

FIG. 6 is a block diagram of the dual universal asynchronous receiver transmitter circuit;

FIG. 7 is a block diagram of the decoder;

FIG. 8 is a block diagram of the random access memory;

FIG. 9 is a block diagram of the erasable programmable read only memory;

FIG. 10 is a block diagram of the horizontal sync generator;

FIG. 11 is a diagram of the connections to the horizontal program array logic;

FIG. 12 is a block diagram of the clock select circuit;

FIG. 13 is a block diagram of the pixel clock;

FIG. 14 is a block diagram of the pattern generator section;

FIG. 15 is a block diagram of the vertical sync generator;

FIG. 16 is a diagram of the connections to the vertical program array logic;

FIG. 17 is a diagram of the connections to the additional vertical program array logic;

FIG. 18 is a block diagram of an enable circuit;

FIG. 19 is a block diagram of a parallel interface timer;

FIG. 20 is a diagram of the connections to the EEPROM;

FIG. 21 is a diagram of the connections to the EEPROM;

FIG. 22 is a block diagram of the right control;

FIG. 23 is a block diagram of the chip select circuit; and

FIGS. 24-42 are flow charts useful in explaining the computing algorythm of the sync generator system.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

All of the exemplifications set out herein illustrate a preferred embodiment of the invention, in one form thereof. Such exemplifications are not to be construed as limiting the scope of the disclosure or the scope of the invention in any.

Referring first to FIG. 1A. what is disclosed is a simplified block diagram multiple scan rate test pattern generator for raster scan display devices operating in the range from a 10 kHz to 100 kHz horizontal repetition rate at various numbers of scan lines per field and vertical field rates. FIG. 2A shows the control panel 10 for the system and includes a programmable sync portion 12 and a television test pattern generator section 14. Programmable sync portion 12 includes a keypad 16 by means of which horizontal sync and pattern parameters may be entered in 0.1 microsecond timing increments. Thus the operator may build or synthesize a rate by entering horizontal parameters such as told H line time, H blanking, H sync etc., 0.1 microsecond timing increments.

Vertical parameters are entered in increments of half lines. Vertical parameters such as the number of scan lines in two fields, V blanking, V front porch, V sync etc., are entered in half line increments. The entered parameters and timing are indicated on a 16 segment alpha-numeric display 18. By means of the programmable sync portion 12 the operator may generate or build a rate, one parameter at a time, or may choose standard proportion and format which will be computed automatically. Rates may be stored, recalled for use, edited, or deleted by keypad code entries.

A basic set of test patterns is provided for evaluation of television raster type display devices. Functions are provided to conduct the performance tests for television displays such as Bars, Dots, Window, Gray Scale etc. The functions provided may be used to conduct the performance tests as provided in a publication entitled "Performance Test for Television Display Devices", published by Visual Information Institute, Inc. of Xenia, Ohio, the assignee of the instant invention.

The television test patterns are selected by means of the test pattern selection portion 14. By manipulating selector control knob 24, various test pattern functions may be selected as indicated, such as bars, dots, flat field, etc.

While most of the test functions which may be selected by knob 24 are well known in the prior art and need not be disclosed in great detail herein, the following selections provide functions as follows:

Resolution--this provides a square wave bar pattern at selected repetition rate to a maximum of 30 MHz to develop desired resolution television lines in five increments at full, 100% black to white contrast.

Character--this provides the development of a block "C" with a small "x" superimposed to form rows across the television display screen. The rows are separated by three inactive scanning lines. The number is adjustable, nominally 40-80 per row depending upon scan rate, to a maximum 25 MHz clock rate.

Video--this combines a step resolution burst sequence black reference segment and a ten step gray scale.

Combination--provides in one raster simultaneously the video pattern plus color bars.

The resolution repetition rate selector knob 22 selects the repetition rate for the square wave bar pattern when the selector control knob 24 selects the resolution setting as shown.

The advantage of providing a test pattern generator selectable by means of knob 24 is that the various scan rate parameters for forming a pattern may be recalled from memory. Thus the scan rate parameters may first be entered into the keypad and thereafter the operator can select the test patterns quickly by manipulation of knob 24. As the different test patterns are selected the preset parameters are automatically read from memory to form the raster scan patterns.

Referring now to FIG. 2B what is shown is a schematic diagram of the resolution repetition rate switch 22 and the pattern function select switch 24. It can be seen that the resolution repetition rate switch 22 provides different frequencies for different settings of the switch. Thus the frequencies 10 megahertz to 30 megahertz are provided in 5 megahertz steps.

Function select switch 24 provides an enabling input for the function select circuits by grounding the particular pin selected by the function switch. By grounding the pin a particular input for the selection will be enabled.

In the block diagram of the control system as shown in FIG. 1A the keypad 16 is shown diagrammatically along with the keypad display and RS232 interface 28. The RS232 interface provides communication to and from the keypad display 18. The display portion 18 comprises a fluorescent display with its own processor which converts the serial number information to character data for display on the display screen.

A bus 30 is provided for routing information between the keypad display 28 and a central processing unit (CPU) and program memory 32. The central processing unit comprises a standard MC68008 CPU chip. The program memory comprises an 8K by 8 random access memory (RAM) and a 16K by 8 erasable programmable read only memory EPROM as will be explained hereinafter. The central processing unit and program memory are connected by means of a sync generator bus 34 and a microprocessor control bus 36 to a horizontal generator section 38, a vertical generator section and electronical erasable program read only memory EEPROM storage unit 40 and a sync generator interface unit 42. The sync generator interface unit 42 transmits data to a video development and output conditioning section 44 which in turns transmits information to a CRT display device 46.

Referring to FIG. 1B what is disclosed is a schematic diagram of the inputs to the pattern generator section. The computer sync generator and interface block comprises a combination of the CPU and program memory 32, horizontal generator section 38, vertical generator section and EEPROM storage 40 and sync generator interface 42. Outputs are provided to a pattern generator 43 on bus 47. By means of these inputs the pattern generator generates a video pattern which is routed by means of a bus 49 to a video development and output conditioning circuit 44. FIG. 1A shows how the pattern generator 43 is connected to the sync generator by means of bus 47 and to the pattern select switch 24. Additionally FIG. 1A shows how the pattern generator is connected by bus 49 to video development and output conditioning circuit 44.

Referring now to FIG. 3 there is disclosed a more detailed schematic block diagram of the central processing unit (CPU) and program memory 32. The CPU 48 comprises a standard MC68008 circuit chip which controls the entire system based on a program stored in the memory 62. CPU 48 comprises a 32 bit CPU which transfers 8 bits of information at a time and covers an address space of 1 million bites on the twenty address lines indicated at 50. This CPU is of the asynchronous type and requires an acknowledge when the data is ready. This acknowledgement is provided by the data acknowledge generator (DTACK) 52 on a data acknowledge line 54.

A dual universal asynchronous receiver transmitter (DUART) circuit 56 is provided and comprises a standard MC68681 circuit chip for receiving and transmitting data from and to the display keypad unit 28 and the central processing unit 48. A system clock 58 is provided for controlling the CPU and delivers a 8 MHZ square wave input signal to the CPU.

Two memories are provided for providing information to the microprocessor, an 8K by 8 random access memory RAM and a 16K by 8 erasable programmable read only memory EPROM.

DUART 56 multiplexes the four columns and four rows of the keypad to determine if any keys have been depressed and, if this is found to be true it transmits the entered information in parallel to the microprocessor 48. Additionally, DUART 56 routes this information to the data display 28 for display on screen 18 and to RS232 port which is used to communicate with other peripheral equipment.

EPROM 62 comprises a standard HM27128 16k by 8 memory chip which contains the stored program for controlling the entire system. The CPU picks up the data out of the EPROM at the address it has selected, decodes the data and uses that as an instruction. RAM 60 comprises a standard HM6264 8k by 8 memory chip and contains only program variables, such as the formats. RAM 60 is therefore used in the sense of a scratch pad where the CPU stores all the data it is using. Decoder 64 is a bi-polar PROM which decodes the entire memory map and determines which unit CPU 48 is addressing. Since CPU 48 is asynchronous, when it writes an address it must receive a detect signal to proceed further. This is done by means of the system clock 58 which is used to time the responses of the microprocessor. Thus clock 58 enables the system to adjust to the speed variations between different parts of the system.

The data on bus 66, the address on bus 68 and the control signals on bus 70 are routed through buffers 72, 74, and 76 respectively prior to routing them to other circuit elements, whereby the microprocessor does not have to directly drive those other elements. The buffers are tristated and are enabled until the microprocessor attempts to communicate with elements other than its own circuit board.

Turning now to FIG. 4 what is shown is the data acknowledge generator 52 or DTACK circuit in greater detail. This circuit includes a shift register 84 comprising a standard 74LS164 circuit chip which receives input from data strobe line 80 and clock line 82. Thus if valid data is received on line 80 this information is delayed by means of a signal from system clock 58 via line 82 and shift register 84. If either of RAM 60 or EPROM 62 have been selected the output on DTACK output line 86 will go low. Since EPROM 62 takes longer to respond than the RAM 60 the output on line 86 can be delayed by means of the clock signal on 82. If no signal is detected from RAM 60 or EPROM 62 within 8 clock periods an error output is generated on error output 88 which is fed to the microprocessor and causes a message to be displayed on display screen 18 indicating an error and stopping the machine.

FIG. 5 discloses the microprocessor, clock and buffer circuit in more detail. Microprocessor 48 is 32 bits wide and is connected to data bus 66, address bus 68 and control bus 72, which are respectively connected to buffers 72, 74a, 74b, 76a and 76b. Buffer 72 is a standard 74LS640 circuit chip; buffers 74a and 74b are standard 74LS541 circuit chips; and buffers 76a and 76b are standard 74LS367 circuit chips. The outputs of the buffers are indicated of addresses having the prefix "b" for buffer. System clock 58 is again shown as well as a bussed data acknowledge input 54. Decoder 64 enables line 78 which is shown connected to buffer 76. The buffers are used since CPU 48 cannot drive a bus as explained herein above.

Referring further to FIG. 5 it can be seen that eight data lines are connected to CPU 48. The data lines d0-d7 are bidirectional while the address lines 68 and 72 are unidirectional. Thus the data can be either inputs to or outputs from CPU 48, depending on whether the CPU is reading or writing. If the CPU is writing the data outputs are routed through buffer 72 so that a number of circuits can be driven. Direction of data flow is controlled by address line BWE. The data which are provided as inputs to microprocessor 48 are binary values read from program memory. Data is also provided from the keyboard through the DUART 56. There are 20 address lines to cover 1 megabyte of memory. The lines are unidirectional and become valid after a predetermined delay time such as for instance 80 nanoseconds. By selecting an address a part of the system is enabled which is either read from or written to.

Referring now to FIG. 6 the DUART or dual universal asynchronous receiver transmitter circuit 56 is shown which comprises a standard integrated circuit chip MC68681. The DUART is effectively two serial ports with digital inputs and outputs. It contains 16 registers and the frequency at which the bits are sent to and received by DUART 56 is controllable. This rate is called the "baud" rate. Crystal 57 runs the baud rate clock and the clock rate is typically 1200 HZ. The DUART converts parallel data into serial data and serial data into parallel data at the rate established by the baud rate clock whereby the data can be converted from the parallel format to the serial format and visa versa. The DUART is divided into two sides with one side connected to four address lines and eight data lines. The other side of the DUART is connected to the RS232 serial port by means of 4 lines TXD, RXD, CTS, and RTS. Additionally, this half of the DUART is connected to seven keypad inputs as indicated.

Referring now to FIG. 7 what is disclosed is decoder 64 which comprises a standard circuit chip of the type 74LS571. The decoder comprises a bi-polar PROM which decodes the entire memory map. When the address strobe 90 to the decoder is activated the inputs on address input line A12-A19 cause a section of the memory map to be enabled by one of the four outputs.

FIG. 8 shows RAM 60 which comprises a static RAM circuit chip of the type HM6264. This RAM is a static 8k by 8 RAM having a 65,000 bit capacity which is used by the CPU to store data and formats. It is basically a scratch pad for storing the temporary format values.

FIG. 9 discloses EPROM 62 comprising an integrated circuit chip of the type HM27128. This is an erasable programmable read only memory of the 16k by 8 type. It contains the program for controlling the entire system. It also contains messages and the like which are used in the display during operation of the system. The CPU picks up data out of the EPROM 62 at the address it has selected by means of decoder 64 decodes that data, and uses the data as an instruction.

FIG. 10 discloses a detailed schematic block diagram of the horizontal sync generator. The purpose of the horizontal sync generator circuit is to develop the scan rate information required on a horizontal line for scanning the CRT being tested. The information on the horizontal line comprises video and synchronizing pulses. The horizontal clock produces pulses at 20 MHZ for pulse durations of 50 nanoseconds. As the pulses are counted by the counters 96a, 96b, and 96c, the counts select the locations in horizontal RAM 94 that CPU 48 has written to.

The horizontal RAM 94 comprises twelve 4K by 1 high speed static RAMS. Each static RAM represents one specific output provided by the horizontal sync generator. The 9 horizontal parameters provided by the horizontal output are total horizontal line time, horizontal blanking, horizontal front porch, horizontal sync, 2H serration pulses, 2H equalizing pulses, horizontal drive, horizontal trigger phase and horizontal trigger width. These are also the horizontal parameters which the operator can enter into the keypad to build up the rate. The horizontal front porch parameter is used to develop horizontal sync pulses, and the horizontal trigger phase and width are used to develop horizontal trigger pulses. The parameter input to the horizontal RAM are provided on the twelve date lines d0-d3.

The CPU will run through the seven date lines d0-d7 and then starts over again and runs through lines d0-d3. Thus by loading into RAM 94 the data on the data input lines in 50 nanosecond increments the entire horizontal line can be configured. The data is put into the horizontal RAM in parallel but the information comes out of the horizontal RAM in serial bits. The CPU moves all of the separate pulses into the memory then allows the counters to start at the time base rate of 20 megahertz as it counts from 0 until the counters hit the end of line signal which signifies that the count over.

Counters 96a, 96b, and 96c are standard integrated circuit chips of the type 74F163. Latches 92a and 92b which buffer the outputs from the RAM are standard integrated circuit chips of the type 74F374 and comprise edge-triggered flip-flops. The horizontal clock clocks counters 96a, 96b, and 96c at the 20 Mhz rate so that the RAM has 50 nanoseconds to find the address being addressed and to get the information to the latches before the next pulse comes along. Counters 96a, 96b, and 96care enabled by means of the HEN or horizontal enable line. The HEN signal is provided from a vertical port. Some of the outputs from the latches go to the sync generator circuit and some of the outputs go to the vertical generator section to make up composite pulses.

Referring now to FIG. 11 what is disclosed is the program array logic 104 (PAL) for the horizontal sync generator and comprising a standard microcircuit chip 104 of the type 16R4. Circuit 104 comprises a logic array and four uncommitted flip flops configured as a shift register. The PAL logic array includes a 4 bit shift register which is used to move the write pulse down somewhat from edge to edge so that it is in the center of the select pulse and furthermore generates the chip select signals on lines CS1 and CS2 as indicated. The purpose for the shift register is to match the speed of the RAM 60 to the speed of the CPU 48. A Boolean equation is provided for the operation of the PAL circuit as follows: ##EQU1##

Referring now to FIG. 12 what is disclosed is the horizontal clock which provides the 50 nanosecond time base. Either an external or an internal time base can be provided for generating inputs to a select circuit 106. The reason for using an external clock is that it may be desired to have greater resolution than the 50 nanoseconds provided by the internal clock. If for instance it were denied to generate a pixel based line, an external clock input would be provided through buffer 108. The frequency for the external clock would have to be provided to make the pulses generated come out to exactly the desired number.

By referring to FIG. 13 an illustration of a pixel based clock is shown. A voltage controlled pixel clock oscillator 110 is provided which is controlled by means of a control voltage provided by microprocessor 48 from input control line 112. The pixel clock can also be used to generate a character display by having an output of the oscillator connected to character logic and from there to the video processor.

Referring now to FIG. 15 what is disclosed is a vertical sync generator which operates in much the same way as the horizontal sync generator except that it counts in half lines instead of clock increments. RAM 114 comprises (3) three standard 4k by 12 RAM integrated circuits of the type IMS1420. This circuit is made up of three 4k by 4 static RAMS. A vertical clock input is provided on line 116 and a vertical enable signal is provided on line 118. A common input output line is provided for the data which is isolated by means of buffers 120a and 120b. These buffers may be standard circuit chips of the type 74LS367. The buffers are actuated by means of enable lines EN3 and EN4 as indicated. Latches 122a and 122b are latched to the leading edge of the 2H clock and are enabled by the VEN not line. The latches are standard circuit chips of the type 74LS374. Address latches are provided at 124a, 124b, and 124c and these may be integrated circuits of the type 74LS163. The latches operate as a counter chain in similar fashion to the horizontal sync generator. The data inputs are provided on the lines which are fed to latches 120a and 120b to provide vertical parameter information on the vertical trigger phase and width, vertical front porch, vertical blanking, vertical sync, number of scan lines in two fields, V drive and sync format. For different types of modes such as the broadcast mode the vertical is delayed with the front porch and this can be accomplished by means of the 2H clock.

Referring now to FIG. 18 what is provided is the circuitry to produce the enable signals EN3 and EN4 for the vertical sync generator. Signals on lines CS3 and CS4 are provided to gates 126A and 126B together with the vertical enable signal. The logic provides the enable signal to indicate which side of buffers 120a and 120b of the vertical generator is being written to. Or gates 126a, and 126b may be integrated circuits of the type 74LS32.

Referring now to FIGS. 16 and 17 what is provided is the program array logic. FIG. 16 shows the PAL for providing the composite sync pulses and FIG. 17 shows the PAL for developing the controls for the counter, the EPROM and the parallel port as well as the RAM location being written to in blocks of 4k. The PALS are circuit chips of the type 16L8 and operate according to Boolean equations.

The vertical PAL sync generator of FIG. 16 is programmed with the following equation: ##EQU2##

The vertical PAL sync generator of FIG. 17 is programmed with the following equation: ##EQU3##

Referring now to FIG. 19 what is disclosed is a parallel interface timer 128 or PIT. It is used for two things namely to control the horizontal and vertical sync generators and to enable or disable EEPROM 130. The PIT includes 32 registers. CPU 48 controls all of the inputs and outputs to the PIT. CPU 48 can not write to the horizontal or vertical sync generators while CPU 48 is running because the counters would be at the wrong address. The horizontal and vertical sync generators must be turned on and off to allow CPU 48 to send new data to the sync generators to set up the new parameters for the next line, or frame. PIT 128 also generates the function codes for the PAL'S to enable the preparation of custom composite wave forms controlled by EEPROM 131. When a mode is selected such as Industrial, Military, Custom, etc., an output is generated by the PIT to tell the PAL what sync format to put out.

It can be seen that the horizontal and vertical enable lines for stopping and starting the counters of the horizontal and vertical synchronizing circuits are connected to the pit. The EPEN line is used for enabling the EEPROM 130 and prevents the CPU from accidentally writing in to EEPROM 130 without proper enablement.

FIG. 20 shows the electronically erasable programmable read only memory 130 or EEPROM 130. This circuit stores raster formats and parameters and permits the change of parameters when in the edit mode. It is also possible to lock the EEPROM so that changes to the stored values in the EEPROM cannot be made. Lockout can be provided by requiring a security password to be entered before the edit function can be used. EEPROM must be addressed with an access code in the same way as a static RAM or EPROM.

It is important that the format storage devices can be locked out so that the operator can not change the parameters of the test equipment. The lock out feature allows only recall of parameters but will not allow editing or changing of the parameters.

FIG. 21 shows an additional EEPROM 131 which operates in the same way as EEPROM 130 of FIG. 20. EEPROMS 130 and 131 are standard microcircuits of the type 52B13.

FIGS. 22 and 23 show a write control and chip select control respectively and develop enablement signals on lines EWE and EPR. The EWE signal permits the CPU to write to location while the CPU output is low.

In operation the system may be either user programmed or the internal central processor will automatically calculate the proportional format for the operator's frame and line time requirements as input into the keypad.

If no instructions are provided or the system is switched on and off as for instance by a power failure the system is automatically set up for a "default" proportional 525 lines/60 fields per second format. This prevents damage to a CRT unit being tested.

By using the recall, edit or build modes the operator may develop any format needed within the limits 100 to 2,048 lines in two fields and 10 microseconds to 204 microseconds per horizontal line. Additionally, a number of formats can be stored, the number depending upon the amount of memory available. Therefore a fixed format can be automatically selected or a new format can be built from scratch.

To build a format each parameter can be individually defined or automatically calculated depending upon the initial answers given to the prompted questions posed by the system. Thus the following user parameter entries can be provided.

number of H lines in two fields

horizontal line time

proportional or custom rate

horizontal Blanking

horizontal front porch

horizontal sync

2H serration

2H equalization

horizontal drive

horizontal trigger phase

horizontal trigger width

vertical Blanking

vertical drive

vertical trigger phase

vertical trigger width

sync format

The built up format can either be saved or maybe deleted after use by entering a code number in the keypad.

An existing format may also be edited or modified to fit new specifications. A parameter is requested and the current value along with the parameter name is displayed on the keypad display 18. If it is decided not to change the displayed parameter value, the existing value must be reentered. This is a two step sequence. First of all the system will ask for the parameter code number and then when the name and the current value is displayed the desired new or existing value must be entered. This sequence can be repeated as many times as necessary for any or all of the parameters. If a format has been built or edited the format may be saved by entering a code number into the keypad and also by pushing the "Raster Store" control button 20.

The system also includes means for detecting errors and for displaying errors on the keypad display. If a catastrophic error is encountered the keypad display will show this by displaying that the error has occurred.

The detailed operation of the system is as follows and as disclosed in the system flow charts shown in FIGS. 24-42. When it is desired to recall a rate previously stored, power is applied to the instrument and the 525/60 proportional scan rate broadcast format, will automatically appear. This initial default rate is permanently programmed and cannot be altered. The instrument will return to this default rate whenever power is interrupted. Signals at this rate automatically appear at the output connectors. The operator presses the recall control button and then enters the raster index number desired after looking the raster number up in the raster log index. After the raster number is entered on the keypad the display will show the scan rate, access code number, scan lines in two fields, and vertical rate.

If it is desired to search for a rate previously stored, the operator can survey all the rasters which may be in storage for any particular number of scan lines in two fields. For instance, there could be stored 875/60 Broadcast format, 875/60 Industrial format, 875/50, and 875/37.6. The operator can inspect each one of these formats to verify the raster log listing as follows. The recall control button would be depressed and the raster index number together with the number of scan lines in two fields would be entered. The display will now show the scan rate access code number, the scan lines in two fields and the vertical rate. However, if this rate is not in storage the display will indicate this and the sequence will end. If the display shows that the scanned rate is in storage and then wishes to search for another rate he presses the number of lines in two fields for the new rate into the keypad. If no additional entries are available at that rate the display will indicate this. If the operator, after finding a particular scan rate, wishes to use the rate the operator will press the enter button after which the scan rate display is activated and the sequence will end.

If it is desired to examine or modify the parameters in a scan rate previously stored, the operator, after applying power to the instrument and entering the security password, enters the EDT control letters after which the keyboard display will call for a raster number which the operator will then enter. The keyboard display will then call for a parameter. The operator must then enter the code number for a parameter to be examined. At this point the operator decides whether revision is required, and enters the desired revision or decides that no revision is desired and enters the code for the next parameter to be examined. If, after a parameter is called for the operator wishes to end the editing mode he enters a code into the keypad and then decides whether to save the edited format or to discard it and use it temporarily. If he decides to discard the format he enters a code into the keyboard whereupon the display will show the scan rate access code number, the number of scan lines in two fields and the vertical rate. The operator may use the modified rate temporarily but since it is not stored, it will be erased when another sequence is initiated. Alternatively, if the same code is entered into the keyboard the display will call for an overwrite and the operator can then decide whether to do so or not. At this point the operator can still decide to use the rate temporarily and then to have it erased or can overwrite the scan rate previously stored and end the sequence.

If it is desired to review all rates in storage the operator enters the scan rate access code number. The display will show the scan rate access code number, the number of scan lines in two fields and the vertical rate. Alternatively, the display will indicate that no rate is stored in that position. By continuing to enter new access codes the entire sequence of stored rates can be reviewed.

If it is desired to build a completely new scan rate, power is applied to the instrument, a security password is entered and the proper code is entered. The display will then call for the desired number of lines horizontal line time in increments of 0.1 microseconds which must then be entered. The operator must then choose whether he wishes to build a proportional or a custom scan rate. If a proportional or standard rate is to be built the proper code is entered and the rate is automatically built and the sync format is displayed. If a custom rate is to be built all of the custom parameters should be entered as they are called for on the display, such as horizontal Blanking width, horizontal front porch width, horizontal sync width, etc. At the end of this procedure the sync format is displayed. After the sync format is displayed for either the proportional or custom rate the display calls for the horizontal pattern whereupon the operator selects the custom or standard rate. Additional parameters must be entered for the custom rate as called for. However, if a standard rate is desired the system automatically supplies the parameters and calls for the horizontal bar position information. To finish building the rate for both the custom and the standard rate several other parameters must be entered such as the horizontal bar position, the horizontal bar spacing, the vertical window start, the vertical window stop, and the raster number. After all these parameters have been entered a decision must be made to save the new scan rate or to discard it. If it is to be discarded the rate may be used temporarily as displayed but it will be erased when another sequence is initiated. If it is desired to save the rate a save code is entered in the keypad and the new scan rate is then stored after the raster store button is depressed.

Further details for the operation of the system can be seen in the flow charts of FIGS. 24-42.

The complete source program for the microprocessor circuit is attached to the specification as appendix "A" from which details of the computational programming will be apparent to those skilled in the art.

Attached to the specification is an appendix "B" which comprises a publication entitled "Vii Raster Master Keyboard Entry Programmable Sync Generator". This publication was prepared and published by Visual Information Institute, Inc. of Xenia, Ohio and is incorporated herein by reference. This publication discloses in detail the operation procedure for the television video pattern generator system disclosed in the instant application.

Also, enclosed herewith as appendix "C" is a publication entitled "Vii Product Information Model 2501 Television Test Pattern Generator". This publication was prepared and published by Visual Information Institute, Inc., of Xenia, Ohio and comprises the technical specifications of a television video pattern generator system according to the present invention. The information disclosed in the publication is incorporated into this application by reference.

While this invention has been described as having a preferred design, it will be understood that it is capable of further modification. This application is therefore intended to cover any variations, uses, or adaptations of the invention following the general principles thereof and including such departures from the present disclosure has come within known or customary practice in the art to which the invention pertains and fall within the limits of the amended claims. ##SPC1##