JPH0312736B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printer interface device that can print images by connecting to a multi-gradation raster scan type video terminal having an arbitrary code system.

In recent years, with the advent of printers that can print in color (such as thermal printers),
2. Description of the Related Art Printers that are connected to color video terminals and print images in color identical to those displayed on the terminals have become widely used.

FIG. 1 is a block diagram showing a typical configuration example of the video terminal. In this diagram,
The video terminal 1 has a frame memory 2 that stores one screen worth of dot data (one dot data is 8 bits), and the dot data supplied from the frame memory 2 in red (R), green (G), blue ( B)3
A color information generation circuit 3 having a conversion table for converting colors into digital RGB signals (8 bits each), and a D/A converter (digital/analog converter) 4 for converting these digital RGB signals into analog RGB signals. , display analog RGB signals as images
It is composed of a CRT display device 5.

In order to intercept data (or signals) from this video terminal 1 and perform color printing on the printer, (a) the output of the frame memory 2 (8-bit dot data), (b) the output of the color information generation circuit 3 ( (24-bit digital RGB signal), (c) Output of D/A converter 4 (analog RGB signal)
must be transmitted to the printer.

In this case, method (b) requires a large number of signal bits to be sent, and method (c) requires a wide signal band and requires a high-speed, high-precision A/D converter on the printer side. The disadvantage is that it does not.

Therefore, method (a) is widely used, but in this case, the configuration shown in FIG. 2 was conventionally used. That is, the dot data outputted from the frame memory 2 passes through an 8-bit transmission line 6 and is passed through a code converter 7 having a configuration and operation similar to that of the color information generating circuit 3, and the code converter 7.
The output is supplied to the printer 9 via the printer interface 8, and color printing is performed.

By the way, in the conventional configuration described above, depending on the specifications of the video terminal 1 and the printer 9, a situation may arise in which the conversion rule of the code converter 7 has to be changed, and the connection between the video terminal 1 and the printer 9 may be interrupted. It wasn't easy. That is,
For CRT displays, R (red), G (green),
It is common to use B (blue) as a primary color and display intermediate colors by additively mixing these primary colors;
Color printers generally use C (cyan), M (magenta), and Y (yellow) as primary colors and display intermediate colors by subtractive color mixing of these primary colors. For example, if color information such as "orange" is supplied from the video terminal to the printer interface, the M (magenta) color information of the color printer is ) and Y (yellow), the "orange" colors of the two colors would be slightly different and accurate color printing would not be possible.

In view of the above circumstances, the present invention provides a printer interface device that can be directly connected to a video terminal having an arbitrary code system and perform color printing extremely faithful to the original image. The color image information is converted into printable print information for each primary color based on second conversion data stored in a storage device within the circuit, and the first
The apparatus is characterized in that it has a second converting means for converting the first converted data into the second converted data according to the printable primary colors when the converted data is supplied.

Embodiments of the present invention will be described below based on the drawings.

FIG. 3 shows a printer according to an embodiment of the present invention.
FIG. 2 is a block diagram showing the configuration of main parts of the interface device. In this figure, 11 is a transmission line for exchanging signals with video terminal 1.
Compliant with Centronics interface.
12 is a communication control circuit that controls the exchange of signals. In this case, when the communication control circuit 12 sends a ready signal to the video terminal 1, the video terminal 1 sends 1 byte of data D and the strobe signal STB in parallel. When the communication control circuit 12 receives the strobe signal STB, it reads the data D and issues an acknowledgement.
Return ACK. In this way, data D is received by the communication control circuit 12 in byte units and written to the buffer memory 14 via the RAM 13 (code conversion means). Note that there are two types of received data D: a conversion code, which will be described later, and dot data sent from the frame memory 2.

The RAM 13 stores a conversion table group 13a (see FIG. 4) for converting the code of the received data D, and is an 8K byte medium-high speed static converter.
The address terminals A0 to A7 of the RAM 13 are connected to the output terminal of the communication control circuit 12.
~A12 are connected to the address bus of the CPU 15, and data ends D0~D7 are connected to the data bus 16. Then, from the communication control circuit 12 to the address terminal A
The received data D supplied to 0 to A7 is code-converted by the conversion table group 13a and becomes data Da.
is output from the data terminals D0 to D7 as
Da is written to the buffer memory 14. In this case, the address ends A8 to A12 are controlled by the CPU 15, and each time the value of A8 to A12 changes to "0", "1", "2", "3", etc., the conversion table A, R, , B... are selected, and conversion is performed using these conversion tables. Here, the nth address of conversion table A (n=0, 1, 2
...255) is written with the value n, so that when conversion table A is selected, the input and output of the RAM 13 match. In addition, conversion tables R, G, and B, similar to the conversion table of the color information generation circuit 3 shown in FIG.
It outputs a digital RGB signal with a total of 24 bits. The contents of these conversion tables A, R, G, and B are rewritten by the CPU 15, and the contents of conversion tables A, R, G, and B are rewritten by the CPU 15, and
The contents of G and B are written based on the conversion code sent from the video terminal 1. In addition,
In this embodiment, by changing the values of address ends A8 to A12, it is possible to form 2 ⁵ =32 conversion tables. Further, the above-mentioned components 12 to 16 constitute the printer interface circuit 1.
7 and is installed inside the printer.

Next, the operation of this embodiment will be explained. The operation of this embodiment is based on the conversion code sent from the video terminal 1, and the conversion table R,
During the initial set stage to form G and B, the dot data sent from the frame memory 2 of the video terminal 1 is converted into data Da (digital RGB signal).
The print data set is converted into a print data set and written into the buffer memory 14. Below, these operations will be explained in order.

(1) Initial set.

When the power switch or reset switch (both not shown) of the printer 9 is pressed down, the CPU 15 performs an initial set according to the following procedure.

Write conversion table A. That is, the values "1", "2", "3", . . . are set at the first address, second address, third address, . . . of the conversion table A. This is to match the input and output of the RAM 13 when conversion table A is selected.

The conversion table A is kept selected and the signal is made active to notify the video terminal 1 that reception preparations are complete.

After transmitting a command indicating "I will now send the conversion code," the video terminal 1 transmits the conversion code one byte at a time.
This conversion code is the same as the code in the conversion table of the color information generating circuit 3 shown in FIG. 1, and three bytes (corresponding to each color of R, G, and B) are transmitted for each dot data.

The CPU 15 writes the sent conversion code into the buffer memory 14. In this case, since conversion table A is selected and the input and output of RAM 13 match, the conversion code is written to buffer memory 14 as is.

When all the conversion codes have been sent, the video terminal 1 sends a command indicating that ``transmission of the conversion codes is now complete.''

Upon receiving this command, the CPU 15 sets the signal to high level, stops transmission from the video terminal 1, reads the conversion code written in the buffer memory 14, and sequentially writes it into conversion tables R, G, and B. In this case, it is also possible to write the converted code while performing desired conversion. For example, the conversion codes for R, G, and B colors can be replaced with conversion codes for C (cyan), M (magenta), and Y (yellow).

(2) Setting print data.

When the creation of conversion tables R, G, and B is completed,
The CPU 15 selects the conversion table R and outputs the signal again.
Activate READY. As a result, the video terminal 1 sequentially reads dot data from the frame memory 2 and transmits them to the communication control circuit 12. The dot data received by the communication control circuit 12
When supplied to the RAM 13, the dot data is code-converted by a conversion table R and written to the buffer memory 14 as data Da. In this way, the dot data in the frame memory 2 is read out → transmitted → received → code converted → written to the buffer memory 14 in 1-byte units. And 1
When the data Da for the screen is stored in the buffer memory 14, it is supplied to the printer 9 and dot printing is performed. Thereafter, similar operations are performed for conversion tables G and B, and color printing is performed.

According to this embodiment, since an arbitrary conversion table can be formed in the RAM 13, it is possible to connect the video terminal 1 and the printer 9, which have completely different code systems. Also, video terminal 1
There is no need to convert data according to the specifications of the printer 9 and send it. Furthermore, since subtle color adjustments can be made, color reproducibility is excellent.

Application examples of this embodiment include the following.

By writing a conversion code directly into the RAM 13 independently of the printer, it is possible to cause the printer 9 to print an image having a different color from that of the CRT display device 5 (FIG. 1).

Multiple conversion tables can be assigned to each color of Y, M, and C, increasing the degree of freedom of the device. Also,
It is also possible to prepare separate conversion tables for characters and graphics.

As described above, in the present invention, a rewritable code conversion table is provided in the interface circuit of the printer, so that the printer can be connected to a video terminal having a completely different code system. Furthermore, the video terminal is freed from the inconvenience of having to convert and send data according to printer specifications. Furthermore, since subtle color adjustments can be made, color reproducibility is excellent.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventional video terminal, FIG. 2 is a block diagram showing an example of connection between a conventional video terminal and a printer, and FIG. 3 is a block diagram showing the configuration of a main part of an embodiment of the present invention. The block diagram shown in FIG. 4 is a conceptual diagram showing the structure of the conversion table group 13a provided in the RAM 13. 1...Video terminal, 9...Printer (color printer), 13...RAM (storage device), 1
3a...Conversion table group, 15...CPU (first conversion means, second conversion means), 17...Interface circuit.

Claims (1)

[Claims] 1. A video terminal that stores first conversion data for converting input color image information into display information for each primary color that can be displayed on a display; In order to convert color image information into printable print information for each primary color in a printer interface device that is inserted between a color printer and a color printer that prints based on the input print information for each primary color. a storage device for storing second conversion data of the image data; and when color image information is supplied from the video terminal, converting the color image information into print information for each of the printable primary colors based on the second conversion data; a first converting means for converting; and, when the first converting data is supplied from the video terminal, a first converting means for converting the first converting data into the second converting data according to the printable primary colors; 1. A printer interface device comprising: 2 conversion means.