Computer graphics processing and selective visual display system – Data responsive crt display control – Color display
Reexamination Certificate
2001-03-29
2004-01-06
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Data responsive crt display control
Color display
C345S030000, C345S046000, C345S048000, C345S204000, C345S690000
Reexamination Certificate
active
06674413
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a display control apparatus for displaying data having gradations on a display unit such as a CRT (Cathode Ray Tube) or the like.
BACKGROUND OF THE INVENTION
In recent years, in order to display various kinds of information such as channels, volumes, and the like as characters or graphics on a display unit such as a CRT or the like, a display control apparatus is employed in a television set or the like. This display control apparatus reads display data stored in a ROM in order of display codes stored in a RAM, converts the display data into RGB display data, further converts the RGB display data into analog RGB data having halftones by a DAC (Digital Analog Converter), and displays the analog RGB data on a display unit.
FIG. 3
is a block diagram illustrating a display control apparatus using a conventional technique. A main unit
300
of the display control apparatus displays display data stored in it, on a display unit
110
such as a CRT, on the basis of a display command S
101
supplied from the outside. The display command S
101
, which is a signal instructing to carry out display, is input to a display command input terminal
101
. A CPU (Central Processing Unit)
102
generates a display code S
102
on the basis of the display command S
101
inputted to the display command input terminal
101
. The display code S
102
is a signal corresponding to display data to be displayed. For example, when displaying a character on the display unit
110
, an ASCII code or the like is used as the display code, and the display data corresponding to this display code is bit map data of the character, or the like. The display codes S
102
generated by the CPU
102
are sequentially arranged and stored in a RAM
103
. An address generation controller
104
sequentially reads the display codes S
103
arranged in the RAM
103
and performs arithmetic operation on them to convert the display data into ROM addresses S
104
of a ROM
105
which stores the display data. The ROM
105
outputs the display data S
105
at an address position on the basis of a given ROM address S
104
. The display data S
105
is a 5-bit signal, and it is used to specify
27
display colors to be converted in a color data conversion unit
306
. In the color data conversion unit
306
, a code of a color pallet used to control a DAC
207
is stored. The color data conversion unit
306
converts the 5-bit display data S
105
for specifying the display colors into display color control signals S
306
a
, S
306
b
, and S
306
c
for specifying the display colors of R(Red), G(Green), and B(blue) each comprising 2 bits, on the basis of the color pallet, and outputs these signals. A display control preprocessing unit
350
is composed of the CPU
102
, the RAM
103
, the address generation controller
104
, the ROM
105
, and the color data converter
106
.
The DAC
207
is a current output type DAC receiving the display color control signals S
306
a
, S
306
b
, and S
306
c
corresponding to R, G, and B each having 2 bits, which are output from the display of the display control preprocessing unit
350
. The DAC
207
comprises a DACR
217
corresponding R, a DACG
227
corresponding to G, and a DACB
237
corresponding to B, and grounding resistors RR
3
, RG
3
, and RB
3
which are connected to the outputs of the DACR
217
, the DACG
227
, and the DACB
237
, respectively, to convert current into voltage. The DACR
217
, the DACG
227
, and the DACB
237
perform control of three current outputs of H (high) level, M (Middle) level, and L (low) level, on the basis of the values of the 2-bit display color control signals S
306
a
, S
306
b
, and S
306
c
, respectively, and the current outputs are converted into three voltage levels of H, M, and L, thereby outputting display color data S
107
a
, S
107
b
, and S
107
c
that can be displayed by the display unit
108
.
In the display control apparatus
300
so constructed, when each of the three display color data S
107
a
, S
107
b
, S
107
c
represents the three signal levels, 27 (=3×3×3) states are generated, whereby 27 colors can be displayed. Each of the current output type DACs, i.e., the DACR
217
, DACG
227
, and DACB
237
, is able to control the current outputs of three levels H, M, L, according to the inputted 2-bit display color control signal and, therefore, 27 (=3×3×3) voltage states are realized by the resistors RR
3
, RG
3
, and RB
3
that convert current into voltage.
However, the conventional display control apparatus
300
employs the current output type DACs that are analog circuits. Generally, in contrast with a digital circuit, the characteristics of an analog circuit greatly vary according to the size of a transistor or the capacitance of a capacitor, which are constituents of the analog circuit. Therefore, the manufacturing precision must be kept high to obtain products of uniform quality. Further, the power consumption is increased. Consequently, the conventional display control apparatus has the problems of high manufacturing cost and large power consumption.
SUMMARY OF THE INVENTION
The present invention is made to solve the above-described problems and has for its object to provide a display control apparatus that can perform intermediate color display, with reduced manufacturing cost and reduced power consumption.
Other objects and advantages of the invention will become apparent from the detailed description that follows. The detailed description and specific embodiments described are provided only for illustration since various additions and modifications within the scope of the invention will be apparent to those of skill in the art from the detailed description.
According to a first aspect of the present invention, there is provided a display control apparatus including at least one output control unit, and each output control unit comprises: a tri-state buffer receiving, as a signal input, a one-bit color signal, and receiving, as a control input, a one-bit intermediate color control signal for controlling an intermediate color of the color signal, and setting its output in one of the following three states: a state of outputting a first voltage, a state of outputting a second voltage, and a high impedance state, on the basis of the color signal and the intermediate color control signal; a first resistor having an end connected to a power supply, and the other end connected to the output of the tri-state buffer; and a second resistor having an end connected to the ground, and the other end connected to the output of the tri-state buffer. Therefore, it is possible to provide a display control apparatus that can perform output for intermediate color display, with reduced manufacturing cost and reduced power consumption, by using the tri-state buffer as a digital circuit.
According to a second aspect of the present invention, the display control apparatus of the first aspect includes, as the output control units, an output control unit to which an R color signal is input, an output signal unit to which a G color signal is input, and an output control unit to which a B color signal is input. Therefore, it is possible to provide a display control apparatus that can perform output for intermediate color display, with reduced manufacturing cost and reduced power consumption.
According to a third aspect of the present invention, the display control apparatus of the first aspect including a plurality of the output control units, and the respective output control units receive intermediate color control signals which are independent of one another. Therefore, it is possible to provide a display control apparatus that can perform output for intermediate color display, with reduced manufacturing cost and reduced power consumption.
According to a fourth aspect of the present invention, in the display control apparatus of the first aspect, the output control unit further includes a switch between the power supply and the first resistor, which switch electrically conn
Inoue Masao
Kawashima Keiji
Nakaimuki Masayuki
Kovalick Vincent E.
Shalwala Bipin
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