JP2000280575A - Controller for image output apparatus, image output apparatus, and method for controlling image output apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce electromagnetic radiation noises of an image output apparatus. SOLUTION: A clock frequency modulation circuit 126 for a system and a clock frequency modulation circuit 128 for images which output clock signals obtained by modulating a clock oscillation frequency by a predetermined cycle are used as a clock oscillator at a controller 100. A peak value of electromagnetic radiation noises of an entire printer can be lowered accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller, an image output device, a control method of the image output device, and a clock frequency modulation circuit, and more particularly to a controller, an image output device, and an image output for reducing electromagnetic radiation noise. The present invention relates to a device control method and a clock frequency modulation circuit for reducing electromagnetic radiation noise.

[0002]

2. Description of the Related Art In an image output apparatus such as a printer,
With the progress of high density and digitization, further reduction of electromagnetic radiation noise is required. That is, the image output device is provided with measures against electromagnetic radiation noise (EMI (Electro Magn
etic Interference). This electromagnetic radiation noise is caused by supplying a clock signal having a high clock frequency, for example, a clock frequency of 60 MHz or more to various circuits using a clock wiring or the like.

[0003] Electromagnetic radiation noise usually contains high-frequency components up to several hundred MHz, and must be created from the design stage comprehensively for both electric circuits and mounting structures in consideration of the characteristics of noise sources and propagation paths. is necessary. In addition, by reducing the electromagnetic radiation noise by selecting electric and electronic components and selecting the wiring method, the electromagnetic radiation noise is reduced by taking measures against the electromagnetic radiation noise using filters, housings, ferrite beads, etc. Was.

[0004]

However, in the method of taking measures against electromagnetic radiation noise using a filter, a housing, a ferrite bead, or the like, extra weight is generated until the final stage of product development, or a complicated design is required. The demands and extra costs have placed a heavy burden on product development, sometimes leading to a reduction in signal quality. In particular, as the speed of the printer increases, the cost burden for measures against electromagnetic radiation noise tends to increase.

The present invention has been made in view of the above problems, and has as its object to provide an image output device capable of taking measures against electromagnetic radiation noise at an early stage of product development. That is, an object of the present invention is to provide an image output device using a clock frequency modulation circuit for a clock oscillation circuit that is a source of electromagnetic radiation noise.

[0006]

In order to solve the above problems, a controller according to the present invention is provided with a clock frequency modulation circuit for generating and outputting an operation clock signal obtained by modulating a clock oscillation frequency at a predetermined cycle. An operation clock signal is supplied from the clock frequency modulation circuit to the image control circuit. By using such a clock frequency modulation circuit, the peak value of electromagnetic radiation noise can be reduced.

A drawing timing signal is input to the image control circuit at a predetermined drawing timing from a drawing engine, a reset signal is generated based on the drawing timing signal, and is output to a clock frequency modulation circuit. The clock frequency modulation circuit may reset the cycle for modulating the clock frequency of the operation clock signal based on the reset signal. By doing so, it is possible to make the fluctuation of the image drawn by the drawing engine invisible to the naked eye.

Furthermore, by outputting a drawing timing signal from the drawing engine each time the drawing engine starts drawing of each drawing line, the modulation cycle of the video clock signal can be aligned at the start of each drawing line. it can.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] In a first embodiment of the present invention, a peak value of electromagnetic radiation noise is reduced by using a clock frequency modulation circuit for a clock oscillation circuit which is a source of electromagnetic radiation noise. It is intended to lower it. Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

First, the clock frequency modulation circuit will be described. In recent years, as a countermeasure against electromagnetic radiation noise (EMI countermeasure), a clock frequency modulation circuit that generates a clock signal by changing the frequency at a constant period of ± several percent has been used. This clock frequency modulation circuit includes a spread spectrum clock generator (SSCG: Spre
ad Spectrum Clock Generator). This is to reduce the electromagnetic radiation noise at the level of the clock oscillator that is the source of the electromagnetic radiation noise.As described above, the clock frequency modulation circuit modulates the clock oscillation frequency in a narrow band to specify the frequency. This is a circuit that employs the technology to reduce the frequency radiation intensity.

FIG. 1 is a diagram showing the relationship between the modulation ratio and time when a modulation of ± 1% is performed with a clock frequency of 100 MHz as a basic frequency. FIG. 2 is a diagram showing signal waveforms of clock signals at points a, b, and c in FIG.

As shown in FIG. 1, the clock frequency modulation circuit modulates the clock frequency at a constant period T at ± 1%. For this reason, as shown in FIG. 2A, the clock frequency modulation circuit has a frequency of 101 MHz near point a.
A clock signal is generated and output at a clock frequency of z. As shown in FIG. 2B, the clock frequency modulation circuit generates and outputs a clock signal at a clock frequency of 100 MHz near point b. As shown in FIG. 2C, the clock frequency modulation circuit generates and outputs a clock signal at a clock frequency of 99 MHz near point c. As described above, the clock frequency modulation circuit modulates the clock frequency at a constant cycle T and outputs a clock signal.

FIG. 3 is a graph showing that the frequency modulation of the clock signal reduces the electromagnetic radiation noise. As shown in FIG. 3, by modulating the clock frequency of the generated clock signal, the peak value of electromagnetic radiation noise caused by the clock signal is reduced.

Next, a specific configuration and operation when the present invention is applied to a printer which is an example of an image output apparatus will be described.

FIG. 4 shows a controller 100 and a drawing engine 110 in the printer according to the first embodiment of the present invention.
FIG. 6 is a diagram showing exchange of signals between the control unit and the control unit. FIG. 5 is a diagram showing a timing chart of the horizontal synchronization signal HSYNCX, the video clock signal VCLK, and the video signal VIDEOX.

As shown in FIG. 4, a horizontal synchronization signal HSYNCX is transmitted from the drawing engine 110 to the controller 100. As shown in FIG. 5, this horizontal synchronizing signal HS
YNCX is a signal that goes low at the timing when the drawing engine 110 starts drawing each line, and the controller 100 secures horizontal synchronization based on this signal. This horizontal synchronizing signal forms the drawing timing signal in the present embodiment. As shown in FIG. 4, the controller 100 controls the video signal VID synchronized with the video clock signal VCLK based on the horizontal synchronization signal HSYNCX.
The EOX is output to the drawing engine 110. As shown in FIG. 5, the video signal VIDEOX is a video signal, and the drawing engine 110 takes in the video signal VIDEOX to perform drawing.

FIG. 6 is a block diagram showing the internal configuration of the controller 100. As shown in FIG. 6, the controller 100 mainly includes a CPU (Central Process
ng Unit) 120 and ASIC (Application Specific)
IC) 122 and SDRAM (Synchronous DRAM) 1
24, a system clock frequency modulation circuit 126,
An image clock frequency modulation circuit 128 is provided. The ASIC 122 includes an image control circuit 1
30 are configured.

System clock frequency modulation circuit 126
Are the CPU 120, the ASIC 122, and the SDRAM 124
Is supplied with a clock signal CLK1. In the present embodiment, the clock signal CLK1 is a clock signal that is modulated with a width of ± 1% around 66.6 MHz. AS other than the CPU 120 and the image control circuit 130
The IC 122 and the SDRAM 124 operate in synchronization with the clock signal CLK1. That is, the CPU 12
0 is synchronized with the clock signal CLK1 and the controller 1
00 is performed. The SDRAM 124 is a synchronous DRAM capable of reading and writing data every clock CLK1.

The image clock frequency modulation circuit 128
The clock signal CLK2 is supplied to the image control circuit 130 of the ASIC 122. In the present embodiment, the clock signal CLK2 is a clock signal that is modulated with a width of ± 1% around 40 MHz.

The image control circuit 130 generates a signal based on the clock signal CLK2 and the horizontal synchronizing signal HSYNCX.
A video clock signal VCLK and a video signal VIDEOX synchronized with the video clock signal VCLK are generated. Then, the image control circuit 130 outputs the video signal V
IDEOX is output to the drawing engine 110. The drawing engine 110 generates an image based on the video signal VIDEOX, and actually performs printing.

FIG. 7 is a block diagram showing the internal configuration of the image clock frequency modulation circuit 128 in FIG.
As shown in FIG. 7, the image clock frequency modulation circuit 128 includes an oscillation circuit 140 to which a source vibration from the crystal unit 300 is input, and a PLL (Phase-Lock loop) circuit 14.
2 and an output circuit 146. The oscillation circuit 140 is a kind of a piezoelectric vibrator. The oscillation circuit 140 receives a source vibration from the crystal oscillator 300 and outputs a first internal clock signal having a constant clock frequency.
The PLL circuit multiplies the frequency of the first internal clock signal by a constant and outputs the second internal clock signal having a clock frequency modulated at 40 MHz ± 1% to the output circuit 1.
Output to 46. Output circuit 146 outputs the second internal clock signal as clock signal CLK2.

As described above, according to the printer of this embodiment, since the system clock frequency modulation circuit 126 and the image clock frequency modulation circuit 128 are used as the clock oscillators, the peak value of the electromagnetic radiation noise can be reduced. Can be reduced. That is, since a clock signal obtained by applying a narrow band modulation to the clock frequency is used as the clock oscillator that is the source of the electromagnetic radiation noise, it is possible to suppress the peak of the electromagnetic radiation noise as shown in FIG. it can.

Therefore, the shield and EMI of the printer
Since the number of countermeasures parts can be reduced or reduced, the weight and cost of the product can be reduced. Also, at the stage of system design, reduction of electromagnetic radiation noise can be realized. In addition, the actual radiation attenuation extends over many frequencies, and the higher the frequency of the clock signal, the higher the radiation attenuation can be expected.

Further, the use of the system clock frequency modulation circuit 126 and the image clock frequency modulation circuit 128 simultaneously radiates harmonics of all clock signals and signals synchronized therewith, and address decoder control bus signals. Can be attenuated. In other words, by reducing the electromagnetic radiation noise of the clock signal,
Electromagnetic radiation noise of the entire printer system can be reduced.

[Second Embodiment] In a second embodiment of the present invention, the fluctuation of the printer image cannot be discriminated by human eyes by aligning the phase of the frequency modulation for each drawing line of the video clock signal. Things. Hereinafter, a second embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 8 is a diagram showing the internal configuration of a controller 200 according to the second embodiment of the present invention, and is a diagram corresponding to FIG. 6 of the above-described first embodiment. As shown in FIG. 8, the controller 200 mainly includes the CPU 12
0, an ASIC 122, an SDRAM 124, a system clock frequency modulation circuit 126, and an image clock frequency modulation circuit 228. Of these, CPU 120, ASIC 122, SD
RAM 124 and system clock frequency modulation circuit 1
Reference numeral 26 is the same as in the first embodiment. A
An image control circuit 230 is configured in the SIC 122.

The reset signal SCON_X from the image control circuit 230 is supplied to the image clock frequency modulation circuit 228.
Is entered. Based on the reset signal SCON_X, the image clock frequency modulation circuit 228 resets the cycle of modulating the clock signal CLK2, that is, the modulation phase, and supplies the reset to the image control circuit 130 of the ASIC 122. In the present embodiment, this clock signal CLK2 is 4
This is a clock signal that is modulated with a width of ± 1% around 0 MHz.

The image control circuit 230 generates a signal based on the clock signal CLK2 and the horizontal synchronization signal HSYNCX.
Generate a video signal VIDEOX. Then, the image control circuit 130 outputs the video signal VIDEOX to the drawing engine 110.

FIG. 9 is a diagram showing the internal configuration of the image clock frequency modulation circuit 228 in FIG. 8, and is a diagram corresponding to FIG. 7 of the first embodiment described above. FIG. 10 is a diagram showing a timing chart of the horizontal synchronization signal HSYNCX, the video clock signal VCLK, the video signal VIDEOX, and the reset signal SCON_X according to the second embodiment, and is a diagram corresponding to FIG. 5 of the first embodiment described above. .

As shown in FIG. 9, the image clock frequency modulation circuit 228 includes an oscillation circuit 240 to which a source vibration from the crystal unit 301 is input, a PLL circuit 242, a modulation control circuit 244, and an output circuit 246. And are provided. The oscillation circuit 240 receives a source oscillation from the crystal oscillator 301 and outputs a first internal clock signal having a constant clock frequency. The PLL circuit multiplies the clock frequency of the first internal clock signal by a constant and outputs the same.
A second internal clock signal is output at a clock frequency modulated at 0 MHz ± 1%. The reset signal SCON_X is input to the modulation control circuit 244. As shown in FIG. 10, the reset signal SCON_X is a signal that goes low in response to the horizontal synchronization signal HSYNCX from the drawing engine 110 going low. That is, the reset signal SCON_X is a signal that becomes low each time the drawing engine 110 starts drawing of each drawing line.

As shown in FIG. 9, the third internal clock signal generated by the modulation control signal output from the modulation control circuit 244 and the second clock signal from the PLL circuit 242 is input to the output circuit 246. This output circuit 246
Outputs the third internal clock signal as a clock signal CLK2. That is, the output circuit 246 outputs 40 MHz ±
A clock signal CLK2 that is modulated to a clock frequency of 1% is output. This clock signal CLK2 is a clock signal whose modulation cycle is reset at the timing when the reset signal SCON_X becomes low. That is,
This is a clock signal whose phase is aligned at the timing when the drawing engine 110 starts drawing.

FIG. 11 is a diagram showing a modulation profile of the clock signal CLK2. In FIG. 11, the modulation cycle of the clock signal CLK2 is reset at the start of drawing of each drawing line, and the highest frequency, 40 MHz + 1
The clock frequency starts from a percentage. The clock signal CLK2 having the same modulation period is input to the image control circuit 230 shown in FIG. 8 as the video clock signal VCLK.

FIG. 12 is a flowchart for explaining the processing for generating each signal of the timing chart shown in FIG. As shown in FIG. 12, first, a low-level horizontal synchronization signal HSYNCX is input to the image control circuit 230 from the drawing engine 110 for a certain period (step S10). The image control circuit 230 sets the reset signal SCON_X to a low level for a certain period based on the timing when the horizontal synchronization signal HSYNCX goes low, and outputs it to the image clock frequency modulation circuit 228 (steps S11 and S12).

The image clock frequency modulation circuit 228
The modulation cycle of the clock signal CLK2 is reset at the timing when the reset signal SCON_X becomes low.
In the present embodiment, at this reset timing, the clock signal CLK2 is output to the image control circuit 230 at the highest clock frequency of 40 MHz + 1% (step S13). Based on this clock signal CLK2, the image control circuit 230 outputs the video clock signal VCL
K, and a video signal VIDEOX synchronized with the
Is output to the drawing engine 110 (step S1).
4).

As described above, according to the printer of the present embodiment, the modulation period of the video clock signal VCLK is set to be the same at the start of each drawing line. You can not understand. That is, as shown in FIG. 13, since the dot size of each drawing line in the output image can be aligned with each of the upper and lower drawing lines, it is possible to prevent the image fluctuation from being discriminated by human eyes. Therefore, a clear output image can be obtained even when a signal obtained by performing clock frequency modulation on the video clock signal VCLK is used.

Moreover, as in the first embodiment described above,
Since the system clock frequency modulation circuit 126 and the image clock frequency modulation circuit 228 are used as clock oscillators, the peak value of electromagnetic radiation noise can be reduced.

The present invention is not limited to the above embodiment, but can be variously modified. For example, in the above-described embodiment, a printer as an image output device has been described as an example. Further, the present invention may be applied to an image input device such as a scanner.

Further, in the second embodiment, the horizontal synchronization signal HSYNCX output from the drawing engine 100 at the start of drawing each image line is used as a drawing timing signal, and the reset signal SCON_X is generated based on this signal. However, the present invention is not limited to this timing, and the reset signal SCON_X may be generated at another timing. For example, the reset signal SCON_X may be generated at the timing of drawing in each drawing line or at the timing of drawing end.

[0039]

As described above, according to the present invention,
Since the clock frequency modulation circuit that modulates the oscillation frequency at a predetermined cycle and outputs the operation clock signal is used as the clock oscillator, the peak value of the electromagnetic radiation noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a modulation ratio and time when a clock signal is modulated with a clock frequency.

FIG. 2 is a diagram showing clock signal waveforms at points a, b, and c in FIG.

FIG. 3 is a graph showing the relationship between the frequency span and the intensity of electromagnetic radiation noise before and after applying clock frequency modulation.

FIG. 4 is a view showing a signal transmission / reception relationship between a controller and a drawing engine in the printer according to the first embodiment of the present invention.

FIG. 5 is a timing chart of a horizontal synchronization signal, a video clock signal, and a video signal transmitted and received between a controller and a drawing engine.

FIG. 6 is a diagram showing the internal structure of the controller according to the first embodiment of the present invention.

FIG. 7 is a diagram showing an internal structure of the image clock frequency modulation circuit according to the first embodiment of the present invention.

FIG. 8 is a diagram showing an internal structure of a controller according to a second embodiment of the present invention.

FIG. 9 is a diagram showing an internal structure of an image clock frequency modulation circuit according to a second embodiment of the present invention.

FIG. 10 shows a horizontal synchronization signal, a video clock signal, and a video signal transmitted and received between the controller and the drawing engine;
6 is a timing chart of a reset signal output from the image control circuit to the image clock frequency modulation circuit.

FIG. 11 is a diagram showing a modulation cycle of a clock signal output from an image clock frequency modulation circuit and a timing of a reset signal.

FIG. 12 is a flowchart showing printer processing according to a second embodiment of the present invention.

FIG. 13 is a diagram illustrating a relationship between an output image of a printer and a clock frequency of a video clock signal according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 100 controller 110 drawing engine 120 CPU 122 ASIC 124 SDRAM 126 system clock frequency modulation circuit 128 image clock frequency modulation circuit 130 image control circuit 140 oscillation circuit 142 PLL circuit 228 image clock frequency modulation circuit 230 image control circuit 240 oscillation Circuit 242 PLL circuit 244 Modulation control circuit 246 Output circuit

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[Procedure amendment]

[Submission date] February 24, 2000 (200.2.2
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

An image output device controller, an image output device, and a control method of the image output device

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (10)

[Claims] 1. A controller for outputting a video signal to a drawing engine, comprising: a clock frequency modulation circuit for generating and outputting an operation clock signal obtained by modulating a clock oscillation frequency at a predetermined cycle; and receiving the operation clock signal. Generates a video clock signal based on the operation clock signal,
A controller for generating the video signal synchronized with the video clock signal and outputting the video signal to the drawing engine. 2. An oscillation circuit to which a source oscillation is input, and which generates and outputs a first internal clock signal having a predetermined clock frequency based on the oscillation source, the clock frequency modulation circuit comprising: A phase locked loop circuit that receives the first internal clock signal having a frequency, modulates the clock frequency of the first internal clock signal at the predetermined cycle, and outputs the modulated second internal clock signal as a second internal clock signal; The controller according to claim 1, further comprising: an output circuit configured to output the input second internal clock signal as the operation clock signal. 3. The image control circuit receives a drawing timing signal from the drawing engine at a predetermined drawing timing, generates a reset signal based on the drawing timing signal, and outputs the reset signal to the clock frequency modulation circuit. The controller according to claim 1, wherein the clock frequency modulation circuit resets a cycle for modulating a clock frequency of the operation clock signal based on the reset signal. 4. A drawing timing signal from the drawing engine is output each time the drawing engine starts drawing of each drawing line.
A controller as described in. 5. An oscillation circuit to which a clock signal is input, and which generates and outputs a first internal clock signal having a predetermined clock frequency based on the clock signal, said clock frequency modulation circuit comprising: A phase locked loop circuit that receives the first internal clock signal having a frequency, modulates the clock frequency of the first internal clock signal at the predetermined cycle, and outputs the same as a second internal clock signal; A modulation control circuit that outputs a modulation control signal for resetting a cycle for modulating a clock frequency of the operation clock signal based on the reset signal; and a second internal clock signal output from the phase locked loop circuit. And a third internal clock signal generated by the modulation control signal output from the modulation control circuit. The controller according to claim 3, further comprising: an output circuit that outputs the operation clock signal. 6. An image output apparatus comprising: a controller for outputting a video signal; and a drawing engine for drawing and outputting an image based on the video signal, wherein the controller sets a clock oscillation frequency at a predetermined cycle. A clock frequency modulation circuit that generates and outputs a modulated operation clock signal, and the operation clock signal is input, and a video clock signal is generated based on the operation clock signal;
An image output device, comprising: an image control circuit that generates the video signal synchronized with the video clock signal and outputs the video signal to the drawing engine. 7. An image output apparatus comprising: a controller for outputting a video signal; and a drawing engine for drawing and outputting an image based on the video signal, wherein the controller sets a clock oscillation frequency at a predetermined cycle. A clock frequency modulation circuit that generates and outputs a modulated operation clock signal, and the operation clock signal is input, and a video clock signal is generated based on the operation clock signal;
An image control circuit that generates the video signal synchronized with the video clock signal, and outputs the video signal to the drawing engine. The image control circuit includes a predetermined drawing timing from the drawing engine. A drawing timing signal is input, a reset signal is generated based on the drawing timing signal and output to the clock frequency modulation circuit, and the clock frequency modulation circuit generates a clock signal of the operation clock signal based on the reset signal. An image output device, wherein a period for modulating a frequency is reset. 8. A method for controlling an image output device, comprising: a controller for outputting a video signal; and a drawing engine for drawing and outputting an image based on the video signal, wherein the clock oscillation frequency is modulated at a predetermined cycle. An operation clock generating step of generating and outputting the generated operation clock signal, and generating a video clock signal based on the operation clock signal, and generating the video signal synchronized with the video clock signal, A method of outputting a video signal to a drawing engine. 9. A method for controlling an image output apparatus, comprising: a controller for outputting a video signal; and a drawing engine for drawing and outputting an image based on the video signal, wherein the clock oscillation frequency is modulated at a predetermined cycle. An operation clock generating step of generating and outputting the generated operation clock signal, and generating a video clock signal based on the operation clock signal, and generating the video signal synchronized with the video clock signal, A video signal output step of outputting to a drawing engine; a reset signal generating step of generating a reset signal based on a drawing timing signal input from the drawing engine at a predetermined drawing timing; and the operation clock signal based on the reset signal. Resetting the cycle of modulating the clock frequency of the Method of controlling an image output apparatus comprising: a. 10. A clock frequency modulation circuit for generating and outputting an operation clock signal obtained by modulating a clock oscillation frequency at a predetermined cycle, wherein a source oscillation is input, and a first clock having a predetermined clock frequency is generated based on the source oscillation. An oscillation circuit that generates and outputs an internal clock signal; and the first internal clock signal of the predetermined clock frequency is input from the oscillation circuit, and the clock frequency of the first internal clock signal is modulated at a predetermined cycle to generate a second clock signal. (2) a phase-locked loop circuit that outputs as an internal clock signal, a modulation control circuit that outputs a modulation control signal for resetting a cycle for modulating the clock frequency of the operation clock signal based on an input reset signal, The second internal clock signal output from the synchronous loop circuit and the modulation control output from the modulation control circuit A clock frequency modulation circuit, comprising: a third internal clock signal generated by the signal and an input circuit, and an output circuit that outputs the third internal clock signal as the operation clock signal.