JPH06130925A - Control signal transmission system - Google Patents

Abstract

PURPOSE:To provide a control signal transmission system which reduces the number of signal lines required for signal line connection between an image processing part and an image forming part and the number of elements used for the drivers of signal transmission lines. CONSTITUTION:The image processing part 11 and an image forming part 12 are connected by N signal transmission lines, and N-1 transmission lines out of them are used as a data transmission path 13 shared between image signals and control signals, and the other transmission line is used as a transmission path 15 for an identification signal indicating the attribute of transmission signals; and when the image processing part 11 sends a control signal, the control signal attribute is sent as the identification signal and N-1 or less data transmission lines 13 are used to transmit the control signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control signal transmission system for a graphic printing device such as a printer or a copying machine, or other graphic display device, which handles digital image signals and digital device control signals.

[0002]

2. Description of the Related Art Generally, an image processing unit and an image forming unit are indispensable as main components of a signal processing system in the internal structure of a graphic printing apparatus such as a printer or a copying machine. FIG. 3 is a simplified block diagram of a signal processing system of such a graphic printing apparatus.

Here, the image processing unit receives print data from an externally connected computer or the like via an external interface, performs format conversion or correction of image data, or performs processing such as generation of character shape data. Image data is delivered to the image forming unit in a predetermined format. On the other hand, the image forming unit receives the image data from the image processing unit and forms an actual drawing by electrical or chemical means.

As means used for image formation, an electrophotographic system is used in which an electrostatic latent image is formed by scanning a charged photoconductor with a laser beam modulated with an image signal and then developing the electrostatic latent image. Various types have been devised and used, such as a thermal transfer system in which a recording ink is melted by a thermal head and transferred to a recording paper. Although detailed description of the mechanism of these image forming means is omitted, most of them have a movable mechanism portion for moving the recording head or recording medium, controlling the image forming process, and the like. Therefore, the image forming unit is shown in FIG.
As shown in Fig. 2, it is divided into a device driver section that converts image data into drive signals for laser diodes and thermal heads, and a process control section that controls the image forming process by driving a mechanism section such as head feed and paper feed. To be Normally, the image data signal sent by the image processing unit is mainly sent to the device driver unit, but separately, the image processing unit sends an instruction to the image forming unit to start and end the image forming process and a parameter related to the process. You need to make settings. That is, a transmission line for such control signals is needed.

FIG. 4 shows a conventional example relating to the signal line connection between the image processing section and the image forming section in the configuration of the graphic printing apparatus briefly described above. Here, the image processing unit 41
The book image data transmission line 43 is connected to the image forming unit 42. The image signal is transmitted by the clock signal line 4
4 is transferred in synchronism with the synchronous clock signal transmitted by 4. That is, the image data output from the transmission 8-bit width flip-flop 47 of the image processing unit 41 is determined at the rising edge timing of the synchronous clock signal, and the reception 8-bit width of the image forming unit 42 is transmitted via the image data transmission line 43. It is transmitted to the input of the flip-flop 48. Then, at the next falling edge timing of the synchronous clock signal, the image forming unit 42 takes in the image data from the receiving 8-bit width flip-flop 48.

On the other hand, two transmission lines 45 and 46 are used as control signal transmission lines for the image processing unit 41 to instruct the image forming unit 42 to control the image forming process. Here, the transmission line 45 is for instructing various operation from the image processing unit 41 to the image forming unit 42, and the transmission line 46 is for operating state and error occurrence to the image processing unit 41 from the image forming unit 42. It is for reporting information of. These control signals are serially transferred in an asynchronous manner.

Although not shown in FIG. 4, a ground line for a return pair is prepared for each transmission line.

[0008]

However, in the conventional method described above, the image data transmission line and the control signal transmission line are independent of each other in the signal line connection between the image processing unit and the image forming unit. Since it is provided in the above, a large number of signal lines are required for connection. Further, from the viewpoint of electrical characteristics of transmission, in some applications where a connector must be used for connection, separate connectors must be prepared for the image data transmission line and the control signal transmission line. Therefore, there is a tendency that problems such as an increase in labor for connecting the connector, a space limitation in terms of wiring arrangement, and a large number of elements used for a driver of the transmission line are required.

[0009]

In order to overcome such a problem, in the control signal transmission system of the present invention, a connection for signal transmission between the image processing unit and the image forming unit is (N-1).
Where N is the data bit width of the image signal, N signal transmission lines are used. Then, among them, (N-1) transmission lines are used as a data transmission line for sharing an image signal and a control signal, and the remaining one is an identification signal transmission indicating the attributes of the transmission signals on the (N-1) transmission lines. Use as a road.

[0010]

The control signal transmission of the present invention according to the above-described system operates as follows.

When the image processing section prepares the image data to be printed, first, it sends a control signal such as an instruction for initializing the printing operation to the image forming section, so that the data transmission path controls the identification signal transmission line. Drive to a signal value that indicates that it is used to transmit a signal. The logical value of this signal may be 0 or 1 depending on the agreement of the system to be realized. After that, the image processing unit sends a control signal to the image forming unit using the data transmission path. At this time, the image forming unit receives the signal value of the identification signal, determines that the data transmission path is used for transmitting the control signal, and treats the data sent from the image processing unit as the control signal for processing. To do.

Next, when the image processing section sends the image data for printing to the image forming section, the image processing section sets the identification signal transmission line to a signal value indicating that the data transmission path is used for transmitting the image data signal. To drive. After that, the image processing unit sends the image data to the image forming unit in a predetermined format using the data transmission path. At this time, the image forming unit receives the signal value of the identification signal, determines that the data transmission path is used for transmitting image data, and treats the data sent from the image processing unit as image data for processing. To do.

The data format used when the image processing section sends the image data to the image forming section may be arbitrary, but at least a pause period for image data transmission needs to exist. Here, the data transmission pause period is a period during which no page data transmission is required between each page image data transmission if image data for one page is transmitted collectively, for example, a raster format image. If data is sequentially transmitted line by line, it means a period during which line data transmission is not necessary between each line image data transmission. In the control signal transmission system of the present invention, the control signal is transmitted by utilizing the idle period of the image data transmission.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a transmission circuit constructed using the control signal transmission system according to the present invention. Here, the image processing unit 11 uses the eight data transmission lines 1
3, the synchronous clock transmission line 14 and the identification signal transmission line 15 are connected to the image forming unit 12. In addition, in this embodiment, all transmission signals use the TTL level.

First, the operation of the circuit of this embodiment during control data transmission will be described. The image processing unit 11 receives print data via an external interface (not shown), performs format conversion and correction of the image data, performs processing such as generation of character shape data, and generates image data to be printed. Store in the frame buffer.
Then, when a print start command is sent from the external interface, the image processing unit 11 transmits a control signal to the image forming unit 12 via the data transmission line 13 in order to initialize the printing operation and set various parameters at the time of printing. Used for. This is done by the following procedure.

The image processing section 11 includes an identification signal transmission line 15
Are driven to "1" to indicate that the data transmission line 13 is used to transmit control signals. Then, the outputs of the data transmission 8-bit width flip-flops 16 all become high impedance, and at the same time, the outputs of the data reception 8-bit width flip-flops 17 of the image forming unit 12 connected by the identification signal transmission line 15 also have high impedance. Becomes On the other hand, at this time, the control signal transmitting three-state driver 18a, the state signal receiving three-state buffer 18b, and the image forming unit 12 of the image processing unit 11 at this time.
The outputs of the state signal transmitting three-state driver 19b and the control signal receiving three-state buffer 19a are activated.

Therefore, the control signal TxC issued by the image processing unit 11 is transmitted to the signal RxC of the image forming unit 12, and the status signal TxS emitted from the image forming unit 12 is transmitted to the signal RxS of the image processing unit 11. In this embodiment, these control signals are serially transferred in an asynchronous manner.
Therefore, although not shown in FIG. 1, the image processing unit 11 and the image forming unit 12 are equipped with an asynchronous communication control circuit, which controls the transmission protocol of control data.

Next, the operation of the circuit of this embodiment during image data transmission will be described. The image processing unit 11 includes the image forming unit 12 described above.
After completing the initialization of the printing operation and the setting of various parameters for printing, the image data is transferred. For this reason, it is necessary to use the data transmission line 13 for the transmission of image data, which is performed in the following procedure.

The image processing section 11 includes an identification signal transmission line 15
Are driven to "0" to indicate that the data transmission line 13 is used for transmitting image data. Then, all the outputs of the data transmission 8-bit width flip-flops 16 are activated, and at the same time, the outputs of the data reception 8-bit width flip-flops 17 of the image forming unit 12 connected by the identification signal transmission line 15 are also activated. To be done. On the other hand, at this time, the control signal transmission three-state driver 18a of the image processing unit 11 and the state signal reception three-state buffer 1
8b, and the outputs of the state signal transmitting three-state driver 19b and the control signal receiving three-state buffer 19a of the image forming unit 12 have high impedance.
Therefore, the image data SD0 issued by the image processing unit 11
SD7 is transmitted to signals RD0 to RD7 of the image forming unit 12.

In this embodiment, this image data transmission is transferred in synchronization with the synchronous clock signal transmitted by the synchronous clock signal line 14. That is, the image data output from the data transmission 8-bit width flip-flop 16 of the image processing unit 11 is determined at the rising edge timing of the synchronous clock signal CLK, and the data reception line 8 of the image forming unit 12 is received via the data transmission line 13. It is transmitted to the input of the bit width flip-flop 17. Then, the synchronous clock signal CLK
At the next falling edge timing of, the image forming unit 12 takes in the image data from the data receiving 8-bit width flip-flop 17.

During the transfer of the image data, the state signal receiving three-state buffer 18b of the image processing section 11 is received.
Since each output of the control signal receiving three-state buffer 19a of the image forming unit 12 is fixed to 0 by the pull-down resistor R, an erroneous signal is not regarded as control data.

As described above, both the image data and the control signal can be transmitted using the same data transmission line.

In the above description, the identification signal transmission line 15 is mainly driven according to whether the image processing unit 11 transmits the control signal or the image data. However, the raster format image data transmission is performed. In applications where it is used, for example, it is possible to configure the horizontal synchronizing signal to act as an identification signal transmission line. Here, the image data in the raster format means that an image is divided into vertical and horizontal pixels, and pixel data for one horizontal line is collectively treated as line data. That is, in the transmission of raster format image data, the operation of collectively sending pixel data for one line in a continuous manner is repeated for the number of raster lines forming an image. In many cases, it is possible to provide a rest period.

FIG. 2 shows an example of the horizontal synchronizing signal timing when transmitting raster format image data.
The period in which YNC is "0" represents that the image data DATA is valid. Signals 21 and 22 in the figure are raster format image data for one line, respectively. Here, during the period when HSYNC is "1", it is not necessary to carry valid data as image data on DATA, so that it can be used for other purposes. Therefore, instead of the identification signal transmission line 15 in FIG. 1, the horizontal synchronization signal HSYNC having the timing shown in FIG. 2 can be used. This causes the horizontal synchronization signal HS to be sent to the image processing unit 11.
This is realized by preparing a transmission controller that performs control such as sending a control signal to TxC after detecting that YNC has changed from “0” to “1”. The code number 23 in FIG. 2 indicates such a horizontal synchronizing signal HSY.
The control signal is transmitted using the period in which NC is "1".

Although the control signal transmission system according to the present invention has been described above with reference to simple examples, the present invention is not limited to the examples given here, and modifications can be made without departing from the spirit of the present invention. Is possible. For example, in this example,
Only two data transmission lines are used as data transmission lines for asynchronous communication for transmitting control signals.
It is easily conceivable to assign some of the data transmission lines of the book to control signal transmission for flow control.

[0027]

As described above in detail, according to the control signal transmission system of the present invention, the number of signal lines required for signal line connection between the image processing section and the image forming section can be reduced. Further, since only one connector is required for connection, connection mistakes and labor can be reduced, and elements used for the driver of the transmission line can be saved.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing horizontal sync signal timing in raster format image data transmission.

FIG. 3 is a block diagram showing an example of a signal processing system configuration of the graphic printing apparatus.

FIG. 4 is a circuit diagram showing a conventional example of signal line connection between an image processing unit and an image forming unit in the configuration of the graphic printing apparatus.

[Explanation of symbols]

 11 image processing unit 12 image forming unit 13 data transmission line 14 synchronous clock transmission line 15 identification signal transmission line 16 8-bit width flip-flop for data transmission 17 8-bit width flip-flop for data reception 18a control signal transmission three-state driver 18b state Three-state buffer 19a for signal reception Three-state buffer for control signal reception 19b Three-state driver for state signal transmission 21 One line raster format image data 22 One line raster format image data 23 Control signal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H04N 1/40 Z 9068-5C

Claims (1)

[Claims] 1. A control signal transmission system in a system in which an image processing section sends out a digital image signal and a digital control signal, and an image forming section receives and processes the digital image signal and the digital control signal. The image processing unit and the image forming unit are connected by N (where N is a natural number of 2 or more) signal transmission lines, of which (N-1)
The one transmission line is used as a data transmission line for an image signal or a control signal, and the other one is used as a transmission line for an identification signal indicating the attribute of the transmission signal, and the image processing unit sends the control signal to the image forming unit. In case,
A control signal transmission method characterized in that control signals are transmitted using (N-1) or less data transmission lines while transmitting control signal attributes as identification signals.