JPH08237411A - Image data print system and printer controller - Google Patents

Abstract

PURPOSE: To make print quality stable by confirming objectively an error of image data on a transmission line sent from the printer controller to a printer. CONSTITUTION: When the printer controller 30 outputs image data expanded in an image memory 5 to a printer 20, the printer 20 receives the image data and uses a printer engine 21 to print out the data or to send back the data from a printer engine interface driver 23. The printer controller 30 receives the sent-back image data, compares the data with image data outputted from a comparator 35 and sets an error flag to an error detection register 36 when even one bit is dissident in both the data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image composed of a printer control device for outputting image data expanded in an image memory and a printer or digital copying machine for receiving and printing the image data output from the printer control device. The present invention relates to a data printing system and a printer control device thereof.

[0002]

2. Description of the Related Art A printer controller for outputting image data expanded in an image memory to a color printer, which is a color printer, for printing through a video interface, and a digital copying machine as a printer are used. In this case, the present inventor has previously invented a printer control device capable of inputting image data read from the scanner through a video interface and storing the same in an image memory (Japanese Patent Application No. 5-203342).

FIG. 9 shows an example of the configuration of an image data printing system having the former printer control device. In this image data printing system, a printer control device 3 is connected between a host computer 1 and a color printer (printing device) 2. The printer control device 3 includes a microcomputer (CPU) 4 and an image memory 5 for storing image data for printing (printing) for at least one page for each color.
A video interface 6 capable of parallel transfer of image data for each color, a selector 7 interposed between each image memory 5 and the video interface 6, and an address control section 8.
It has and.

In this configuration, the user uses a host computer (including a word processor, a personal computer having a document creating / editing function, etc.) 1 to create an image for printing one page in a page description language represented by Postscript. . Since the page description language is represented by vectors, whether characters or figures, whether straight lines or curved lines, the image data is sent from the host computer 1 to the printer control device 3 and converted into image data to be actually printed by the CPU 4. It is converted and developed in the image memory 5.

When all the image data for one page sent from the host computer 1 has been stored in the image memory 5,
The CPU 4 detects whether the system of the color printer 2 connected to the video interface 6 is a 1-drum machine or a 4-drum machine. If the detected system is a one-drum machine, only one color can be transferred in one toner transfer operation. Therefore, when printing a color image, the image data is red, green, blue (RGB). ), The data must be sent three times when stored in the image memory 5 and four times when stored in cyan, magenta, yellow, and black (CMYK).

Therefore, the CPU 4 first informs the selector 7 that the system of the currently connected color printer 2 is a one-drum machine, and the color data to be printed is shown in Table 1.
The code shown in Table 2 is transmitted to the selector 7 (for example, the code is “00” if it is “cyan data”), and Table 2 shows which data line on the video interface 6 the image data is output. Selector 7 with code 2
Tell. That is, a total of 5 from the CPU 4 to the selector 7.
The bit data line conveys the type of the connected color printer, the color to be printed, and the information of the data line to be output on the video interface 6.

[0007]

[Table 1]

[0008]

[Table 2]

In the address control unit 8, a frame gate (FG) showing a state in which the color printer 2 is actually printing.
ATE) signal, a line synchronization (LSYNC) signal that specifies the start of a print line, and a pixel clock that counts the dots to be printed, and generates an address on the image memory 5 in which the image data to be output is stored. To do. The selector 7 sends the image data of the color designated by the CPU 4 to the video interface 6 and causes the color printer 2 to print (print).

When the printing of one color is completed, the FGATE signal is negated, so that the CPU 4 starts the printing operation of the second color. The printing operation for the second and subsequent colors is performed in the same manner as for the first color, and when the printing of the three or four colors is completed, the printing of the image data for one page stored in the image memory 5 is completed.

On the other hand, if the color printer 2 is a four-drum machine, printing operations of four colors can be performed simultaneously. Therefore, the CPU 4 of the printer control device 3 uses the four-drum color printer system currently connected to the selector 7. The selector 7 sends the image data of the image memory 5 to each of the data lines of the video interface 6 at the same time in three or four colors, and causes the color printer 2 to print one page. The flow of the above operation is shown in the flowchart of FIG. With this configuration, it is possible to connect both the color printers of the one-drum machine and the four-drum machine with the common printer control device without changing the hardware.

FIG. 11 shows a structural example of an image forming system using a color digital copying machine as a printing device.
In this case, the digital copying machine 2'scans a color printer for printing color image data and scans an image on the paper to read it, and outputs red, green and blue (RGB) image data one color at a time or three colors at a time. Equipped with a scanner.

The digital copying machine 2'can input the image data from the scanner to the printer controller 3'through the video interface 6, and at that time, at least one page of image data to be printed is stored in the image memory 5.
Store for each color. The CPU 4 can recognize the scanner system of the digital copying machine 2'connected to the printer control device 3 '. The video interface 6 is
Bidirectional parallel transfer of image data can be performed for each color.

Further, the printer control device 3'includes
Clock selector 10, work memory 12, RGB output latch 13, CMYK output latch 14, line buffer 15, pull-up resistor 16, scanner latch 1
8. A scanner buffer 19 and the like are provided. In this image forming system, the image data from the image memory 5 is read as R
The data is temporarily stored in the line buffer 15 through the GB output latch 13 and the CMYK output latch 14.

However, the clock for storing the image data in the line buffer 15 is the SYSCLK switched by the clock selector 10. When the image data is read from the line buffer 15, the pixel clock CLK (which is sent from the digital copying machine 2 ') switched by the clock selector 10 is used, and the read image data is sent to the digital copying machine 2'through the video interface 6. To print.

At this time, white data is written in the margin area by the pull-up resistor 16. When the image data read by the scanner of the digital copying machine 2'is loaded, the image data read by the scanner is loaded through the video interface 6, and the scanner buffer 19 is used.
Is temporarily stored in the line buffer 15 via. However,
The clock when stored in the line buffer 15 is the pixel clock CLK switched by the clock selector 10.

When the image data is read from the line buffer 15, the S switched by the clock selector 10 is selected.
It is read by YSCLK, but S is generally used from the pixel clock.
Since YSCLK has a higher frequency, it is read after accumulating one line in the main scanning direction. The image data output from the line buffer 15 is stored in the image memory 5 through the scanner latch 18. At that time, white data is written in the margin area by the pull-up resistor 16.

In general, the data read by the scanner is RGB data unless color conversion processing is performed, so that the inversion latch is not necessary. By performing such an operation, one printer control device can utilize both the printer function and the scanner function of the digital copying machine.

[0019]

However, in the printer control device in such an image forming system,
Since it is composed of one video interface, it is possible to check whether the image data expanded in the image memory was originally intended for printing, and to check the error on the transmission line when sending the image data to the printer. Since the check is performed by visually inspecting the printed image by an inspector, there is a problem that an error cannot be detected in a fine portion and a quantitative value cannot be obtained.

The present invention has been made in view of the above points, and whether the image data developed in the image memory in the printer control device and sent to the printer (printing device) was originally intended to be printed. The objective is to stabilize the quality of the printed image by making it possible to objectively check the error on the transmission path when sending the image data to the printer.

Further, a digital copying machine is used as a printing device so that the image data read from the scanner can be taken into the printer control device and used.
It is also an object to be able to objectively confirm whether the image data was originally intended to be printed or to confirm an error on the transmission path when the image data is sent to the digital copying machine.

Furthermore, in the digital copying machine, the image data read by the scanner can be objectively checked for errors on the transmission path when the image data read by the scanner is sent to the printer controller. It is also an object to improve the quality when storing in the image memory in the control device. Alternatively, even if a printer (printer or digital copying machine) is not connected to the printer control device, it is possible to easily confirm whether the image data expanded in the image memory was originally intended to be printed. It is also intended to improve operability.

[0023]

In order to achieve the above object, the present invention provides a printer control device for outputting image data expanded in an image memory, and image data output from the printer control device for printing. In an image data printing system including a printer, the printer is provided with image data input means for receiving image data output from the printer control device, and image data returning means for returning the image data received by the image data as it is, Output means for outputting the image data expanded in the image memory to the printer control device, input means for inputting the image data sent back from the printer, image data output from the output means and the image input to the input means The comparison means for comparing the data is provided.

Further, a printer control device for outputting the image data expanded in the image memory, a scanner for reading an image on a paper surface and outputting the image data, an image data read by the scanner and an image data received from the printer control device. In an image data printing system including a digital copying machine having a printer for printing, the digital copying machine receives image data output from the printer control device and image data input means for receiving the image data. Image data returning means for returning the image data as it is and image data output means for outputting the image data read by the scanner to the printer control device are provided.

Output means for outputting the image data expanded in the image memory, input means for inputting the image data from the image data returning means and the image data output means of the digital copying machine, to the printer control device, Comparing means for comparing the image data output from the output means with the image data returned from the printer control device input to the input means, and the image data read by the scanner input to the input means in the image memory There is also provided an image data printing system provided with a writing processing unit that develops and writes to.

Further, in the image data printing system, the printer control device is provided with means for returning the image data read by the scanner input to the input means from the output means as it is, and the scanner is provided in the digital copying machine. It is preferable to provide a comparison means for comparing the read image data with the image data received by the image data input means and returned from the printer control device.

Further, in the printer control device for outputting the image data expanded in the image memory to the printer for printing, the output means for outputting the image data to be printed, the input means for inputting the image data, and the above There is also provided one having a loopback means for connecting the output means and the input means, and a comparison means for comparing the image data output from the output means with the image data input to the input means.

[0028]

In the image data printing system according to the present invention, when the printer controller outputs the image data expanded in the memory to the printer, the printer can receive and print the image data, but the image data is sent back as it is. The printer controller can input the returned image data and compare it with the output image data. As a result, it is possible to objectively check whether the image data expanded in the image memory by the printer control device was originally intended to be printed, and check the error on the transmission line when sending the image data to the printer. As a result, the quality of the printed image can be stabilized.

Further, according to the image data printing system of the present invention in which the printer control device is connected to the digital copying machine instead of the printer, when the printer control device outputs the image data expanded in the memory to the digital copying machine, the digital copying is performed. The machine can receive the image data and print it by the printer unit, but the image data can also be sent back as it is. Further, the image data read by the scanner is printed by the printer unit during normal copying, but the read image data can also be output to the printer control device.

The printer controller can input the image data returned from the digital copying machine and compare it with the output image data. It is also possible to input image data read by a scanner of a digital copying machine, develop it in an image memory, and write it. Therefore,
It is possible to objectively check whether the image data expanded in the image memory by the printer control device was originally intended to be printed, and to check the error on the transmission line when sending the image data to the digital copying machine. In addition, since the image data read by the scanner of the digital copying machine can be taken into the printer control device and developed, the function can be improved.

In this image data printing system, the printer controller can also send back the image data read by the scanner, which is input from the digital copying machine, as it is, and the digital copying machine can print the image data read by the scanner and the printer controller. By comparing the image data sent back from the printer, it is possible to objectively check the error on the transmission line when sending the image data to the printer control device, and the image data read by the scanner is sent to the printer control device. It is possible to improve the quality when storing.

Further, even if a printer or a digital copying machine is not connected to the printer control device, the image data output by the printer control device is input again through the loopback means, and the output image data and the input image data are input. By comparing with, it is possible to easily confirm whether or not the image data expanded in the image memory was originally intended to be printed, and the operability can be improved.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block configuration diagram of an image data printing system showing a first embodiment (embodiment of claim 1) of the present invention, and parts corresponding to those in FIG. 9 and FIG. There is.

This image data printing system is composed of a host computer 1, a printer 20, and a printer control device 30 inserted between them. The printer 20 includes a printer engine 21, a printer engine interface receiver 22 which is a video interface, and a printer engine interface driver 23.

In the printer control device 30, in addition to the CPU 4 and the image memory 5, an image control unit 31, a serial interface 32, an interface driver 33 which is a video interface, and an interface receiver 3 are provided.
4, a comparator (comparing means) 35, an error detection register 36, an image memory writing circuit (writing processing means) 3
7, and a CPU bus 38.

In this embodiment, first, the operation for printing the image data sent from the host computer 1 will be described. In response to a command from the host computer 1, the CPU 4 expands the image data written in the page description language into the image memory 5 by the image memory writing circuit 37 so that the image data can be printed by the printer 20. When the image data to be printed for one page has been developed in the image memory 5, the CPU 4 checks whether or not the printer 20 can print through the serial interface 32 in order to execute the printing.

However, since the CPU 4 and the printer 20 always exchange commands with the shared memory, all communication between the CPU 4 and the printer 20 is performed via the serial interface 32. When it is detected that the printer 20 is available, the CPU
Reference numeral 4 issues a print execution command to the printer 20.

In the printer 20, in response to a print execution command from the CPU 4, the printer engine 21 outputs from the printer engine interface driver 23 an FGATE signal (a signal indicating that printing is in progress), an LSYNC signal (synchronization signal of the main scanning direction line), and a CLOCK signal. Signal (pixel clock)
, And waits for image data from the printer control device 30.

The image control section 31 of the printer control device 30 notified of the start of printing by the FGATE signal
4 is interrupted, the image data stored in the image memory 5 is DMA transferred using the CPU bus 38, and the printer 2 is transferred through the interface driver 33.
0 printer engine interface receiver 22
Output to. On the printer 20 side, the printer engine interface receiver 22 receives the image data and outputs it to the printer engine 21 to execute printing. At the end of printing, the FGATE signal is negated, so the image controller 3 of the printer controller 30
It is detected by 1 and the CPU 4 is interrupted.

As a result, the CPU 4 expands the image data of the page to be printed next, if any, into the image memory 5 again, and repeats the above-mentioned processing. If so, the process ends. By such an operation, printing of the image data created by the host computer 1 can be executed. The flow of processing by the printer control device 30 in this case is shown in the flowchart of FIG.

Next, a description will be given of the processing for detecting an error that has occurred in the transmission path on the video interface, and FIG. 3 showing the processing flow by the printer control device 30 in that case.
Refer to the flowchart of. In this case as well, the CPU 4 of the printer control device 30 and the printer 20 exchange the same signals as in printing, but an error detection command is issued instead of a print execution command. When an error detection command is issued from the CPU 4, the printer engine interface receiver 22 on the printer 20 side does not send the image data received from the interface driver 33 of the printer control device 30 to the printer engine 21, but the printer engine interface driver. 23
To the interface receiver 34 of the printer control device 30 through a video interface different from that at the time of reception.

In the printer controller 30, the interface receiver 34 receives the returned image data and sends it to the comparator 35. The comparator 35 compares the returned image data with the image data sent from the interface driver 33, and if any one of the image data for one page has a different value, it sets a flag in the error detection register 36. , Indicates that an error has occurred on the transmission path to the printer 20. And FGA
When the TE signal is negated, the CPU 4 can check the contents of the error detection register 36 to know whether an error has occurred. By such an operation, it is possible to detect an error on the transmission path.

Next, a second embodiment of the present invention (embodiment of claim 2) will be described with reference to FIGS. FIG. 4 is a block diagram of the image data printing system.
The same parts as those in FIG. In this image data printing system, a digital copying machine 20 'is connected to a printer controller 30 instead of the printer 20 shown in FIG. The digital copier 2
0'includes a scanner 24 and a selector 25 in addition to the same configuration as the printer 20 in FIG.

The operation of this embodiment will be described. Image data created by the host computer 1 is transferred to the digital copying machine 2
When printing with 0 ', the same operation as in the first embodiment is executed. That is, the image data written in the page description language from the host computer 1 is transferred to the printer control device 3
When 0 is input, the CPU 4 causes the image memory writing circuit 37
Then, the image data is developed in the image memory 5 by the image control unit 31, and the image control unit 31 outputs the image data page by page from the interface driver 33 to the digital copying machine 2.
Send to 0 '.

The digital copying machine 20 'receives the image data by the printer engine interface receiver 22, and the printer engine interface receiver 22 receives the image data.
Send to 1 and print. This operation is repeated until there is no image data on the page to be printed, and the processing is ended. The operation of detecting an error on the transmission line between the printer control device 30 and the digital copying machine 20 'is substantially the same as that of the first embodiment, but the digital copying machine 20' is used.
In order to send back the image data received from the printer control device 30 as it is, the printer engine interface receiver 22 sends the image data to the printer engine interface driver 23 through the selector 25.

The image data obtained by reading the image of the original document by the scanner 24 is sent to the printer engine 21 through the selector 25 to be printed when a copy command is issued. However, when the error detection command is issued, the selector 25 switches to output the output of the printer engine interface receiver 22 to the printer engine interface driver 23 as described above. When a scanner command is issued from the CPU 4 of the printer control device 30, the selector 25 switches so that the image data output from the scanner 24 is output to the printer engine interface driver 23.

The image data output from the printer engine interface driver 23 is received by the interface receiver 34 of the printer controller 20, and when the scanner command is issued, it is sent to the image memory writing circuit 37. In the image memory writing circuit 37,
The address of the image memory 5 to which the image data from the scanner 24 is to be written is designated in advance by the CPU 4, and the interface receiver 34
Image data received from the image memory 5 by DMA transfer
Write in.

By performing such an operation, the image data read by the scanner 24 of the digital copying machine 20 'can be expanded and stored in the image memory 5 in the printer control device 30. The flow of processing by the printer control device 30 in this case is shown in the flowchart of FIG.

Next, a third embodiment of the present invention (embodiment of claim 3) will be described with reference to FIGS. 6 and 7. FIG. 6 is a block diagram of the image data printing system.
The same parts as those in FIG. This image data printing system also has a digital copying machine connected to the printer controller. The digital copying machine 20 ″ includes a scanner comparator (comparing means) 26 and a scanner error detection register 27 in addition to the configuration of the digital copying machine 20 ′ shown in FIG.

In this embodiment, when the scanner error detection command is issued, the image memory writing circuit 37 of the printer control device 30 does not write the image data in the image memory 5. Instead, the image data read by the scanner 24 of the digital copying machine 20 ″ is transferred to the selector 25
Through the printer engine / interface driver 23 to the interface receiver 34 of the printer control device 30 and at the same time the scanner comparator 26
Also send to.

The printer controller 30 sends the image data received by the interface receiver 34 to the CPU bus 3
8 is sent back from the interface driver 33. The digital copying machine 20 ″ receives the image data sent back by the printer engine interface receiver 22 and sends it to the scanner comparator 26. In the scanner comparator 26, the image data read by the scanner 24 and sent to the printer control device 30 ,
The image data returned from the printer engine / interface receiver 22 is compared, and if there is a different value for even one dot in the scan data for one scan, it is determined that there is a scanner error, and the scanner error detection register Flag 27.

The CPU 4 of the printer control device 30 can know whether or not an error has occurred by referring to the flag of the scanner error detection register 27 in the digital copying machine 20 "by a command through the serial signal line. By such an operation, the CPU 4 can detect an error on the transmission path of the image data read by the scanner 24. The flow of processing by the printer control device 30 at this time is shown in the flowchart of FIG.

Next, a fourth embodiment of the present invention (embodiment of claim 4) will be described with reference to FIG. FIG. 6 is a block configuration diagram of the stem, and the same portions as those in FIG. 1 are denoted by the same reference numerals and the description thereof will be omitted.

Printer control unit 3 in this embodiment
0'includes a pseudo control signal generation circuit 39 in addition to the configuration of the printer control device 30 shown in FIG. Then, instead of the printer 20 in the first embodiment, a loopback connector 40, which is a loopback means, is connected to the interface driver 33 and the interface receiver 3.
4 and the loop-back connector 40 is provided with a pseudo-control signal generated by the pseudo-control-signal generating circuit 39 so that the output image data can be directly returned through the loop-back connector 40. .

This is used at the time of shipping inspection of the printer controller in the factory, and it is not necessary to connect a printer such as a printer or a digital copying machine to the printer controller. In this case, since there is no printer that sends out the FGATE signal, the LSYNC signal, the pixel clock (CLOCK) and the like, the pseudo control signal generation circuit 39 causes the FGA
The TE signal, the LSYNC signal, and the pixel clock signal are generated and output to the loopback connector 40.

The comparator 35 of this embodiment compares the image data returned from the loopback connector 40 with the image data sent from the interface driver 33, and a different value is detected even for one dot in one page. If so, it is determined that there is an error, and a flag is set in the error detection register 36. By performing such an operation, it is possible to confirm whether the developed image data was originally intended to be printed without connecting a printer or a digital copying machine to the printer control device.

[0057]

As described above, according to the image data printing system of the present invention, when the printer controller outputs the image data to the printer or the digital copying machine and prints it, Since it can be compared with the image data sent back, you can check whether the image data expanded in the image memory was originally intended to be printed, check the error on the transmission line when sending the image data, etc. Can be performed objectively, and the quality of the printed image can be stabilized.

Further, in the image data printing system using the digital copying machine instead of the printer, in addition to the above-mentioned effect, the image data read by the scanner of the digital copying machine is output to the printer control device, and the printer control device outputs the image data. Since it can be taken into the device and expanded in the image memory, it becomes possible to realize the improvement of the function. In that case, in the digital copying machine, by comparing the image data read by the scanner with the image data sent back from the printer control device, it is possible to objectively check the error on the transmission line when sending the image data to the printer control device. You can

Further, even if a printer or a digital copying machine is not connected to the printer control device, the image data output by the printer control device is input again through the loopback means, and the output image data and the input image data are input. By comparing with, it is possible to easily confirm whether or not the image data developed in the image memory was originally intended to be printed, and the operability can be improved.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an image data printing system showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing a processing flow when a print command is executed by the printer control device 30 in the embodiment of FIG.

FIG. 3 is a flowchart showing the flow of processing when the error detection instruction is executed.

FIG. 4 is a block configuration diagram of an image data printing system showing a second embodiment of the present invention.

5 is a flowchart showing a processing flow when a scanner command is executed by the printer control device 30 in the embodiment of FIG.

FIG. 6 is a block configuration diagram of an image data printing system showing a third embodiment of the present invention.

FIG. 7 is a flowchart showing a processing flow when a scanner error detection command is executed by the printer control device 30 in the embodiment of FIG.

FIG. 8 is a block configuration diagram of a system showing a fourth embodiment of the present invention.

FIG. 9 is a block configuration diagram of an image data printing system using the printer control device invented above.

10 is a flowchart showing a flow of processing by the printer control device of FIG.

FIG. 11 is a block configuration diagram of an image data printing system using another printer control device invented above.

[Explanation of symbols]

 1: Host computer 4: CPU (microcomputer) 5: Image memory 31: Image control unit 20: Printer 20 ', 20 ": Digital copying machine 21: Printer engine 22: Printer engine interface receiver 23: Printer engine interface Driver 24: Scanner 25: Selector 26: Scanner comparator 27: Scanner error detection register 30, 30 ': Printer controller 32: Serial interface 33: Interface driver 34: Interface receiver 35: Comparator 36: Error detection register 37: Image memory writing Circuit 38: CPU bus 39: Pseudo control signal generation circuit 40: Loopback connector

Claims (4)

[Claims] 1. An image data printing system comprising a printer control device for outputting image data expanded in an image memory and a printer for receiving and printing the image data output from the printer control device, wherein the printer comprises: Image data input means for receiving image data output from the printer control device, and image data return means for returning the image data received by the means as it is are provided, and the image data expanded in the image memory is output to the printer control device. Output means, input means for inputting image data sent back from the printer, and comparison means for comparing the image data output from the output means with the image data input to the input means. Characteristic image data printing system. 2. A printer control device for outputting image data expanded in an image memory, a scanner for reading an image on a paper and outputting the image data, image data read by the scanner, and image data received from the printer control device. In an image data printing system including a digital copying machine having a printer for printing the image, an image data input means for receiving image data output from the printer control device in the digital copying machine, and an image received by the means. Image data returning means for returning data as it is, and image data output means for outputting image data read by the scanner to the printer control device are provided, and output for outputting image data expanded in an image memory to the printer control device. And means for returning image data of the digital copying machine Input means for inputting image data from the stage and the image data output means, and comparing means for comparing the image data output from the output means with the image data returned from the printer control device input to the input means. An image data printing system, further comprising: a writing processing unit that expands and writes the image data input by the input unit and read by the scanner into the image memory. 3. The image data printing system according to claim 2, wherein the printer control device is provided with a unit for returning the image data read by the scanner, which is input to the input unit, from the output unit as it is, the digital copying. An image data printing system, wherein the machine is provided with a comparison means for comparing the image data read by the scanner with the image data received by the image data input means and returned from the printer control device. 4. A printer control device for outputting image data expanded in an image memory to a printer for printing, an output means for outputting image data to be printed, an input means for inputting the image data, and A printer control device comprising: a loopback means for connecting an output means and an input means, and a comparison means for comparing the image data output from the output means with the image data input to the input means.