JPH044688A - Video printer - Google Patents

Abstract

PURPOSE:To reduce the transfer time of a picture data by using a thermal head control circuit so as to stop a read address counter only at output of a read access inhibit signal and applying changeover control to a selector to the position of an address counter thereby eliminating a loss time of picture data readout. CONSTITUTION:When a video signal is inputted at first based on a prescribed picture signal, a read access inhibit signal is outputted from an access inhibit signal generating circuit 9 in response to a horizontal synchronizing signal inputted to a control circuit 3 to a thermal head control circuit 8 and a selector 6. Thus, the selector 6 is thrown to the position of a write address counter 4 and a write address signal is outputted from the write address counter 4 to a line memory 2, in which the picture data of the video signal is written in the line memory 2. The one picture data is written for one read access inhibit period and the picture data by one line are written for one frame period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video printer, and particularly to a video printer for properly printing images on a television, computer CRT, or the like.

[Conventional technology]

2. Description of the Related Art Conventionally, many video printers have been used to make hard copies of images on televisions, computer CRTs, and the like.

FIG. 3 shows such a conventional video printer, in which a video signal is input to a line memory 2 via an A/D conversion circuit 1. Each line memory 2 has 1
It is divided into two banks each having a memory capacity for one line. The horizontal synchronization signal and the vertical synchronization signal are input to the control circuit 3.

The control circuit 3 also includes a write address counter 4 that outputs an address signal that specifies the write address of the video signal to the line memory 2, and an address signal that specifies the read address of the video signal from the line memory 2. Read address counter 5 to output
are connected to each other. These write address counter 4 and read address counter 5 are configured to switch the address signals from the write address counter 4 and read address counter 5 and output them to the line memory 2 based on a switching signal output from the control circuit 3. A selector 6 is connected thereto. moreover,
The control circuit 3 is connected to the line memory 2, and the control circuit 3 outputs control signals for writing and reading video signals by the line memory 2 to the line memory 2. .

The control circuit 3 also includes a thermal head 7.
A thermal head control circuit 8 is connected to drive and control the thermal head control circuit 8.
Based on the transfer request signal output from the line memory 2 to the control circuit 3, the image data of the video signal in the line memory 2 is sent to the thermal head control circuit 8, and the thermal head 7 is driven and controlled based on this image data to obtain a desired result. It is designed to print images.

In the conventional video printer, one line of image data of a video signal representing the screen to be printed is
Image data is written to the line memory 2 in one frame period, and the image data written in this line memory 2 is read out and printed in one frame period. Writing and reading of this line memory 2 are performed as follows. The timing is controlled separately for each horizontal period.

That is, as shown in FIG. 4, the image data of the video signal is written to the line memory 2 during the blanking period of the horizontal synchronizing signal, while the image data is read out during the blanking period of the horizontal synchronizing signal. This is performed for a predetermined period from a predetermined timing after the blanking period, and the number of image data read in one horizontal period is arbitrary based on the access speed of the line memory 2 and the maximum data transfer speed to the thermal radar 7. is set to the value of

Then, when printing a desired image such as a TV screen,
A transfer request signal is output from the thermal head control circuit 8 to the control circuit 3, and based on this transfer request signal, the control circuit 3 switches the selector 6 to read the read address signal from the read address counter 5 to the line memory 2. At the same time, the control circuit 3 outputs a read control signal to the line memory 2. This reads the image data at the address based on the address signal and sends it to the thermal head control circuit 8. For example, when the number of pixels in one line is 512, the image data is transferred in one horizontal period. If the number of image data is 128, it will take four horizontal periods to transfer one line of image data. Then, by driving and controlling the thermal head 7 based on this image data, a desired image is printed.

[Problem to be solved by the invention]

However, in the conventional video printer, the image data is read from the line memory 2 based on a predetermined timing after the blanking period of the horizontal synchronization signal, so there is a loss of time in reading the image data. Moreover, since the number of read data in the horizontal period is fixed, there is a period in the horizontal period in which no reading is performed, and as a result, the image data transfer speed becomes extremely slow. have. For example, in the case of a video printer that can express 64 gradations, image data of 63 gradations is transferred in one line printing, but the time it takes to print one gradation is about 150 μsec, The problem is that the data transfer time is at least 256 μsec, and the data transfer time is longer than the printing time, making it impossible to perform high-speed printing.

The present invention has been made in view of these points, and it is an object of the present invention to provide a video printer that eliminates lost time in reading image data, reduces image data transfer time, and can perform high-speed printing. That is.

[Means to solve the problem]

In order to achieve the above object, the video printer according to the present invention connects a line memory for writing image data of a video signal to a control circuit for outputting a control signal for writing and reading the image data, and also connects a control circuit for outputting control signals for writing and reading the image data. Write and read address counters that output address signals for writing and reading image data are connected via a selector, and a thermal head control circuit is provided that drives and controls the thermal head based on the image data transferred from the line memory. In the video printer, an access prohibition signal generation circuit is provided that outputs a read access prohibition signal for prohibiting reading of image data to the selector and the thermal head control circuit every cycle of the horizontal synchronization signal from the control circuit. , the thermal head control circuit is characterized in that the read address counter is stopped only when the read access prohibition signal is output, and the selector is controlled to be switched to the write address counter side. .

[For production]

According to the present invention, when a video signal based on a predetermined image signal is input, a read access prohibition signal is sent from the access prohibition signal generation circuit to the thermal head control circuit and the selector every cycle of the horizontal synchronization signal input to the control circuit. The selector is switched to the write address counter side, a write address signal is output from the write address counter to the line memory, and the image data of the video signal is loaded into the line memory. On the other hand, when reading image data from the line memory, the selector is switched to the read address counter side without the read access prohibition signal being output from the access prohibition signal generation circuit, and the data is sent to the thermal head. Depending on the transfer status of image data, a control signal is output from the thermal head control circuit to a read address counter, causing the read address counter to output a read address signal to the line memory, and at the same time, a read control signal is output from the control circuit to the line memory. As a result, the image data of the address based on the address signal is read out and sent to the thermal head control circuit, and the desired image can be printed by driving and controlling the thermal head based on this image data. It is something.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.
The same parts as in FIGS. 3 and 4 will be described with the same reference numerals.

FIG. 1 shows an embodiment of a control circuit for a video printer according to the present invention.
The horizontal synchronizing signal and the vertical synchronizing signal are input to a control circuit 3 via a line memory 2 having a capacity for two lines.

Further, the control circuit 3 is connected to a write address counter 4 that outputs an address signal specifying the write address of the video signal to the line memory 2. The control circuit 3 outputs control signals for writing and reading video signals by the line memory 2 to the line memory 2.

Further, an access prohibition signal generation circuit 9 that generates a read access prohibition signal in response to the horizontal synchronization signal is connected to the control circuit 3. A thermal head control circuit 8 is connected thereto. A read address counter 5 that outputs an address signal specifying a read address of the video signal from the line memory 2 is connected to the thermal head control circuit 8.
According to the transfer state of image data to the thermal head 7, a control signal is output to the read address counter 65 at times other than when the read access prohibition signal is generated from the access prohibition signal generation circuit 9, and the read address counter 5.

Further, the write address counter 4 and the read address counter 5 are configured such that an address signal is output from the write address counter 4 to the line memory 2 only when a read access prohibition signal is output from the access prohibition signal generation circuit 9. A selector 6 for switching address signals is connected to.

Next, the operation of this embodiment will be explained with reference to FIG. 2.

First, when a video signal based on a predetermined image signal is input, a read access prohibition signal is sent from the access prohibition signal generation circuit 9 to the thermal head control circuit 8 and the selector 6 in accordance with the horizontal synchronization signal input to the control circuit 3. The selector 6 is switched to the write address counter 4 side, a write address signal is output from the write address counter 4 to the line memory 2, and image data of the video signal is written to the line memory 2. One piece of image data is written in one read access prohibition period, and one line of image data is written in one frame period.

Furthermore, when reading out image data, such as when printing a desired image of a television screen, etc., in this embodiment,
When the read access prohibition signal is not output from the access prohibition signal generation circuit 9, the selector 6 is switched to the read address counter 5 side, and the thermal The head control circuit 8 outputs an ill wJ times signal to the read address counter 5, causes the read address counter 5 to output a read address signal to the line memory 2, and outputs a read control signal from the control circuit 3 to the line memory 2. .

Thereby, the image data at the address based on the address signal is read out and sent to the thermal head control circuit 8, and the desired image is produced by driving and controlling the -maru head 7 based on this image data. It is designed to be used for printing.

Therefore, in this embodiment, all periods other than the time when the read access prohibition signal is outputted by the access prohibition signal generation circuit 9 are defined as the read period of the line memory 2,
Regardless of the horizontal synchronization signal, reading can be performed according to the transfer status of image data to the thermal radar 7, so there is no lost time in reading image data, and the image data to the thermal radar 7 can be read out. The transfer time can be significantly shortened, and as a result, the printing speed can be increased.

Note that the present invention is not limited to the above embodiments,
Various changes can be made as necessary.

〔Effect of the invention〕

As described above, in the video printer according to the present invention, the entire period other than the time when the read access prohibition signal is output from the access prohibition signal generation circuit is the read period of the line memory, and regardless of the horizontal synchronization signal, the thermal head is Since reading can be performed according to the image data transfer status of the thermal head, there is no loss time in reading image data, and the time required to transfer image data to the thermal head can be significantly shortened. This has effects such as being able to increase the printing speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a video printer control device according to the present invention, FIG. 2 is a timing chart showing line memory write and read operations by the control circuit shown in FIG. 1, and FIG. 3 is a conventional FIG. 4 is a block diagram showing the control circuit of the video printer shown in FIG. 2... line memory, 3... control circuit, 4
...Write address counter, 5...Read address counter, 6...Selector, 7...Thermal head, 8...Thermal head control circuit, 9...
- Access prohibition signal generation circuit.

Claims (1)

[Claims] A control circuit that outputs a control signal for writing and reading the image data is connected to a line memory in which image data of a video signal is written, and a write circuit that outputs an address signal for writing and reading the image data in the line memory. In a video printer, a read address counter is connected via a selector, and a thermal head control circuit is arranged to drive and control a thermal head based on image data transferred from the line memory, and horizontal synchronization from the control circuit is provided. An access prohibition signal generation circuit is provided that outputs a read access prohibition signal for prohibiting reading of image data to the selector and the thermal head control circuit every signal cycle, and the thermal head control circuit outputs the read access prohibition signal. A video printer characterized in that the read address counter is stopped only when the read address counter is turned off, and the selector is controlled to switch to the write address counter side.