KR890007274Y1 - Contrast control circuits of crt display devices - Google Patents

Abstract

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Description

Contrast Control of CRT Display

1 is a circuit diagram of the present invention.

* Explanation of symbols for main parts of the drawings

1,2: D flip-flop 3,4,5,9,11,14: Inverter

6,7,8,10,12: resistor 13: switch

DC: Dot clock B8: Protection area display signal

Vin: Serial video signal DB ₀ -DB ₁ : Contrast control data

LATCH: Latch Signal

The present invention relates to a cathode ray tube (CRT) display device for displaying the output of a computer main body on a screen. Specifically, a protected field and an unprotected area of a character displayed on a CRT screen are shown. A contrast control circuit of a CRT display device for adjusting the contrast of only one area of an unprotected field.

In displaying the character output of the computer main body on the screen of the CRT, the screen of the CRT is divided into a protected area and an unprotected area according to the program of the computer main body. The protected area is currently located on the screen. Even though the data cannot be rewritten at the location, it means an area where characters can not be rewritten. The unprotected area means an area where characters can be rewritten by entering data where the current cursor is located on the screen. it means.

Dividing the screen of the CRT into this protected area and the unprotected area is intended to facilitate document processing. The same format is obtained by inputting a document format that does not change in the protected area and inputting variable data in the unprotected area. It is convenient to create several documents.

Recently, due to the use of a word processor and activation, it is frequently used to distinguish between the protected area and the unprotected area, and accordingly, the necessity of adjusting the contrast for only one of the two areas is increasing. Conventional CRT display control device has a knob for contrast adjustment on the outside, so when the contrast of the screen is adjusted with this knob, the contrast of the entire screen is adjusted, and the contrast between the protected area and the unprotected area can not be adjusted so that the document can There is a problem that the editing is not easy and the fatigue of the user's eyes increases.

Therefore, the present invention focuses on making the highest bit of the 8-bit character signal high " H " when using the protection area in a conventional CRT display device, and controls the contrast by a signal indicating the protection area and the unprotected area of the character data. It is an object of the present invention to provide a contrast control circuit of a CRT display device for controlling the contrast of only one of a protected area or an unprotected area by operating a latch circuit in which data is latched.

The present invention for achieving this purpose is a circuit for adjusting contrast on a CRT screen by mixing a serial video signal and a contrast adjustment data signal, and when the contrast of the protection area displayed on the screen is adjusted, the protection area display signal in a high state. An inverter for enabling the latch circuit in which the contrast adjustment data is latched by inverting the low state to a low state, a switch for applying a low state signal to the latch circuit when the contrast of the unprotected area displayed on the screen is adjusted; It is made up of a contrast level section including a latch circuit which is enabled by a signal notified by the inverter or switch and adjusts the contrast level of the protection area or non-beam area.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a contrast control circuit of a CRT display device according to the present invention. As shown in FIG. 1, the dot clock DC and the sequential video signal Vin are output as signals from a conventional CRT display device (not shown). The dot clock DC is a clock signal used in the character generator, and the serial video signal Vin is an output signal of the shift register. These signals CD and Vin are applied to the D-flip flop 1. Also D- pulrip-flop (1) of the D ₀ - input terminal, the best bit (B ₈₎ is used as a character signal increased protection zone pyosing circuit of 8 bits is input bar, the most significant bit (B ₈₎ protects the character signal To decide whether or not to do so. That is, as described later, when the most significant bit B ₈ becomes high, the contrast of only the protected area is adjusted. When the most significant bit B ₈ is low level, the contrast of only the unprotected area is adjusted while leaving the protected area unchanged. Can be.

In the circuit shown in FIG. 1, the contrast adjustment data BD ₀ -BD ₂ is a data that can be varied in eight steps from 000-111 as D-flip-flop via a data bus from a central processing unit (not shown). 2) is input to the D-input terminals D ₀ -D ₂ . Contrast adjustment data (DB ₀ -DB ₂ ) supplied to the D-input terminals (D ₀ -D ₂ ) of the D-flip flop (2) is a latch signal output from the decoder circuit (not _shown ) of the central processing unit. The latches are latched to the D flip-flop 2 by (LATCH).

The thus latched data are applied to the low-level signal to the output enable terminal (OE) of the D- flip-flop (2) when the output from the output terminals (Q ₀ ~Q ₂₎ respectively on its output terminal (Q ₀ ~Q ₂₎ It is applied to the A-point via connected inverters 3-5 and resistors 6-8. The contrast adjustment data signal passing through each of the resistors 6 to 7 is output signal Q ₁₁ of the D-flip flop 1 passing through the inverter 9 and the resistor 10, the inverter 11 and the resistor. The output signal Q ₁ of the D-flip flop 1 passed through (12) and the point A are combined and output to the output terminal Vout.

Level of the signal synthesis doenneun herein the contrast of the D- flip-flop (2), the contrast adjustment in the data latch (DB ₁₁ ~DB ₂₎ bars, the protection area, which can be adjusted to a level of 8 steps according to the state of the protection area Explain in detail how to adjust.

First, when the contrast of only the protection area is to be adjusted, the user turns off the switch 13. At this time, the protection area display signal B ₈ is kept high. The signal B ₈ in the following state is inverted to a low state by the inverter 14, and the output enable terminal of the D-flop flop 2 is performed. Is applied to (OE). On the other hand, in the D-flip flop 2, the contrast lighting data DB _{0 to} DB ₂ transmitted from the central control unit by the latch signal LATCH is latched through the D-input terminals D _{0 to} D ₂ . . Therefore, when the state of the output enable terminal OE is low, the contrast adjustment data is latched to the D-flip flop ₂ and outputted from its output terminals Q _{0 to} Q ₂ so that the respective inverters 3 to 5 and The resistors 6 to 8 are applied to the point A.

Here, the contrast level applied to the point A is the highest level when the input state of the flip-flop 2 is D ₀ D ₁ D ₂ = 000, because when D ₀ D ₁ D ₂ = 000, the D-flip flop (2 This is because the output level (Q _{0 to} Q ₂ ) of) is all generated 000 and these are inverted to the high state by the inverter 35 respectively, so the contrast level at point A is the highest.

On the contrary, when D ₀ D ₁ D ₂ = 111, the contrast level is the lowest. Therefore, by changing the values of DB ₀ , DB _{1 and} DB ₂ using a central processing unit (not shown), the contrast of the protected area can be adjusted without affecting the unprotected area.

On the other hand, if you want to adjust the contrast of only the unprotected area without leaving the protected area, the output of the inverter 14 goes high because the protection area display signal D ₆ goes low. Since the air terminal OE that is the output of (2) is in a high state, the contrast adjustment data latched to the D-flip flop 2 is not output. Thus, the user turns on the switch 13 to adjust the contrast of only the unprotected area. When the switch 13 is turned on, the low state signal B ₈ is applied to the output enable terminal OE of the D-flip flop 2 so that the output of the D-flip flop 2 goes to the next stage as described above. The contrast of the unprotected domain can be adjusted by changing the value of the contrast adjustment data DB _{0 to} DB ₂ transmitted.

As described above, the contrast adjustment circuit of the CRT display apparatus can adjust the contrast of only one of the protected area and the unprotected area displayed on the screen in the document processing system, so that the CRT display window is used. It is a feature that allows you to edit documents more easily and with less fatigue.

Claims (1)

In a circuit for adjusting contrast on a CRT screen by mixing a serial video signal and a contrast adjustment data signal, when the contrast of a protection area displayed on the screen is adjusted, the protection area display signal of a high state is inverted to a low state to contrast adjustment data. Inverter for enabling latched latch circuits, a switch for applying a low state signal to the latch circuit when adjusting the contrast of the unprotected region displayed on the screen, and a signal passing through the inverter or the switch And a contrast level determining section including a latch circuit for adjusting the contrast level of the protected area or the unprotected area.