Classifications

• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G5/00—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
  • G09G5/02—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the way in which colour is displayed
  • G09G5/024—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the way in which colour is displayed using colour registers, e.g. to control background, foreground, surface filling

Definitions

• the present invention relates to computers and more particularly to coloured displays for computers.
• Coloured - displays for computers are already well known but most conventional displays require large amounts of memory for producing high resolution graphics in colour as well as complex circuitry.
• an object of the present invention to reduce the amount of memory required in order to provide high resolution graphics in colour.
• this is achieved by considering the display as a matrix of dots in order to provide the graphics and by grouping a multiplicity of dots together for colour purposes . This enable a reduction in the amount of information which is required to be stored and hence a reduction in the amount .of storage required.
• an object of the present invention is to provide less complex circuitry for deriving the conventional U,V,Y signals which are used for PAL television receivers.
• the circuitry is incorporated into the peripheral cells of an uncommitted logic array (ULA) .
• ULA uncommitted logic array
• Figure 1 shows a block circuit diagram of part of the circuit for generating high resolution graphics in colour
• Figure 2 shows a circuit for generating one of the colour difference signals for the PAL system of television
• Figure 3 shows a circuit for generating the other colour difference signal for the PAL system of television
• Figure 4 shows a circuit for generating the luminance signal for the PAL system of television
• Figure 5 shows a detailed circuit diagram of the arrangement shown in Figure 1 and for producing the signals used for the circuits .shown in Figures 2, 3 and 4 « Before, described the invention, it is considered helpful if a general discussion of the graphics is given first.
• a VDU read out for a computer cosnsits of a "page" of characters on the screen of the VDU arranged in rows and columns.
• the size of each character position is such that 8 raster scan lines are required to fully display one row of the display.
• the character locations of the display can be used to display either alpha-numeric symbols or graphical symbols but it will be appreciated that when displaying graphical symbols, the display will be somewhat crude due to the small number of character locations. It has already
• each character location requires ⁇ bytes of data to define the' dot pattern i.e. the pixel pattern in the character location but only 1 byte of data, the attribute byte, for the colour of the character location.
• Each attribute byte comprises a number of bits representing the fore ⁇ ground colour, a number of bits representing the background colour and preferably a bit to indicate whether or not to cause the character location to flash and also preferably a further bit to allow two different levels of illumination to cause particular desired areas to be highlighted.
• a high resolution graphics display can be produced in colour using a memory device, preferably a random access memory of the dynamic type.
• the size of the memory device is a function of the number of pixels and also the number of attribute bytes. With our system of 19 x 256 pixels and 768 character locations, the memory device has to be capable of storing approximately 6k bytes of data for the 19 x 256 pixel pattern plus approximately k of data for the attribute bytes for the '768 character locations.
• each character location consists of eight pixels horizontally by eight rows i.e. TV raster scan lines vertically.
• the memory device In order to generate the raster scan TV picture, the memory device has to be accessed sequentially in a cycle that repeats every TV field.
• the computer For every eight pixels generated, the computer needs two bytes of data from memory, a pixel pattern byte and an attribute byte. These two bytes are loaded into respective intermediate registers from which they then are loaded into further registers.
• the six least significant bits of the attribute byte represent the fore ⁇ ground and background colours.
• a data selector is controlled by the pixel pattern bytes shifted out of their register to select foreground or background colour for each pixel and fed to a colour generator, circuit for generating a 13 bit (R.G.B) signal for each pixel.
• Eigh bit data words are fed from memory (not shown) to eight input pins D to D7-
• the eight bit words are fed in parallel to the inputs of an intermediate pixel pattern latch 10 and an attribute latch 11.
• the latch 10 or the latch 11 is gated by the processor depending on whether the data to be loaded into the latch is pixel pattern data or colour (attribute) data.
• the memory is addressed to sequent ⁇ ially recover the 32 pixel pattern bytes for the 256 pixels for that line. With each of these bytes, a further portion of memory is addressed in order to recover the attribute byte for eight pixels associated therewith " .
• the data in the latch 10 is then transferred to a further latch 15 *
• the bits of data held in the latch 15 are shifted out serially. Each bit represents a pixel and the logical level of each bit determines whether it is a foreground or a background pixel.
• Each bit as it is shifted out is used to gate a 3-channel 2 line to 1 line selector 16 via a logic circuit 17 which will be de-scribed in more detail later.
• the result is a 3-bit R,G, or B signal.
• Attribute data held in latch 11 is likewise trans ⁇ ferred to a further latch 20. It will be recalled that 6 bits of the ⁇ bit data word represent foreground and background colours. These six bits are fed to the data selector 16. The remaining two bits are control bits one for indicating the level of brightness of the display for that pixel, this being indicated by the output labelled HL and the other for indicating whether or not flashing of the pixel is required, this being-indicated by the output labelled FL . Flashing, in this case, is achieved by causing the pixel in question to alternately display the foreground and background colour at a rate determined by a clock signal T.
• the logic circuit 17 contains an inverter 17a for inverting the signal on the output Fl and feeding the inverted signal as an input an OR gate 17b to whose input clock signal T is applied.
• the output of the date 17b is fed as one input to an EX-OR gate 17c whose other input is the data bit indicating a foreground pixel.
• the data selector 16 is conditioned to cause the 3 bits of attribute data indicative of a fore ⁇ ground colour to be fed to the Blue, Red and Green outputs of the selector. If flashing is required, a
• ⁇ S ⁇ signal is cyclically applied to the other input of the EX-OR gate 17c to cause its output to alternate which in turn causes the output from the data selector to alternate the foreground and background colours.
• a further latch 22 and data selector 23 are present. These are used so that the colour of the picture area around the pixel display area on the television screen can be defined to have a different colour to that of the background of the pixel display area.
• This process is repeated along a raster line with 32 pixel pattern bytes being successively fed to the latch 10 while the 32 associated attribute bytes are fed to the latch 11.
• a fresh set of 3 pixel pattern bytes are transferred successively from memory to the latch 10 but the associated attribute bytes are the same as the previous line.
• This process is repeated line by line until ⁇ lines have been displayed. Thereafter a fresh set of attribute bytes are used for the next 8 lines.
• the output of the data selector l6 is an indication of the colour required, it is not in a form which can be utilised by the colour circuits of a conventional television receiver and so further processing of the R.G.B output from the data selector 16 is required.
• a further aspect of the present invention lies in the circuitry used to process the R,G,B signals into the more conventional Y, ⁇ ,V signals.
• Figure 2 shows a circuit for deriving the U signal for a colour television receiver.
• the digital R,G,B outputs from the data selector 16 are combined with sync, blank and burst signals to provide correct phase digital signals in a digital to analogue converter circuit which is shown in Figure 2. It will be seen that the R,G,B signals are now Blue"
• OMPI Green and Red are used to gate a respective transis ⁇ tor switch 31 j 32, 33 to cause varying amounts of base bias to be applied to an output transistor 34•
• Burst signal is also used to gate a transistor 36 which also varies the amount of base bias on transistor 34-
• Burst circuits being connected between the emitter of a control transistor 35 and ground thus varying the current through the control transistor when it is switched on as a function of whether one or more of the switches controlled by the Blue", Green", Red” and Burst is operated.
• Figure 3 shows a circuit similar to Figure 2 but for the V signal. Equivalent parts to Figure 2 are increased by ten in Figure 3 and further description will be omitted except to say that in this case the R,G,B signals are combined with the sync, blank and burst signals to form Red , Green-"-, Blue*, Burst* and Bursts- input signals to transistors 43, 42, 41, 46 and 48 respectivley.
• Figure 4 shows the luminance digital to analogue converter circuit which in addition ot the Red , Green
• Blue . and Sync signals derived from the output of the data selector 16 has a further input TTE which is derived from the highlight data bit in the attribute bytes.
• Green and Blue signals are used to gate transistors 53 ) 52, 51 respectively which are in the emitter circuit of a control transistor 55•
• the HL signal is used to gate a transistor 56 which affects the base current to the control transistor 55-
• the sync signal gates a further transistor 57 which is used to directly control the base bias of the output transistor 54.
• Figure 5 which is made up of Figures 5A, 5B, 5C and 5D shows a detailed circuit diagram showing in detail the construction of the blocks shown in Figure 1 as well as the circuits for producing the correct phase R,G,B signals used in Figures 2, 3 and 4 - Where appropriate the blocks are shown in Figure 5 in broken lines and given the same reference numeral as in. Figure 1.
• the circuits shown in Figures 2, 3 and 4 are contained in the block 60 in Figure 5D.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Computer Hardware Design (AREA)
• General Physics & Mathematics (AREA)
• Theoretical Computer Science (AREA)
• Controls And Circuits For Display Device (AREA)
• Processing Of Color Television Signals (AREA)

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• 1983
  • 1983-04-22 DE DE8383901331T patent/DE3377306D1/de not_active Expired
  • 1983-04-22 WO PCT/GB1983/000119 patent/WO1983003916A1/en active IP Right Grant
  • 1983-04-22 JP JP50153783A patent/JPS59500929A/ja active Pending
  • 1983-04-22 EP EP19830901331 patent/EP0107687B1/de not_active Expired

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