Communication device, communication controlling method, and non-transitory recording medium

A communication device includes a communication circuit and circuitry. The communication circuit executes a function related to communication. The circuitry detects an input signal input to the communication circuit, transitions the communication device between a first power state, and a second power state in which the communication device consumes less power than in the first power state, and changes a clock frequency of the communication circuit. When the input signal is detected in the second power state of the communication device, the circuitry changes the clock frequency of the communication circuit while maintaining the second power state.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2017-224520 filed on Nov. 22, 2017, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

The present invention relates to a communication device, a communication controlling method, and a non-transitory recording medium.

Description of the Related Art

There is a technique of bringing a multifunction peripheral (MFP) into an engine off state in which all engines of the MFP are stopped to reduce power consumption of the MFP in power saving mode. There is also a method of reducing the clock frequency of a central processing unit (CPU) to reduce power consumption of a personal computer (PC), for example. These techniques may be combined to provide a power saving system that reduces power consumption by reducing the clock frequency of the CPU in the engine off state of the MFP. Such a technique of controlling the clock frequency of the CPU includes a technique of a network packet relay device that increases or reduces the clock frequency of the CPU based on a threshold of a CPU usage rate or the difference in power level to thereby control the level of power consumption.

SUMMARY

In one embodiment of this invention, there is provided an improved communication device that includes, for example, a communication circuit and circuitry. The communication circuit executes a function related to communication. The circuitry detects an input signal input to the communication circuit, transitions the communication device between a first power state, and a second power state in which the communication device consumes less power than in the first power state, and changes a clock frequency of the communication circuit. When the input signal is detected in the second power state of the communication device, the circuitry changes the clock frequency of the communication circuit while maintaining the second power state.

In one embodiment of this invention, there is provided an improved communication controlling method for a communication device including a communication circuit that executes a function related to communication. The communication controlling method includes, for example, detecting an input signal input to the communication circuit, transitioning the communication device between a first power state, and a second power state in which the communication device consumes less power than in the first power state, changing a clock frequency of the communication circuit, and when the input signal is detected in the second power state of the communication device, changing the clock frequency of the communication circuit while maintaining the second power state.

In one embodiment of this invention, there is provided a non-transitory recording medium storing a plurality of instructions for a communication device including a communication circuit that executes a function related to communication. When executed by one or more processors, the plurality of instructions cause the processors to perform the above-described communication controlling method.

DETAILED DESCRIPTION

If the existing power saving system for reducing the clock frequency of the CPU is directly applied to an MFP with a facsimile (FAX) function, the MFP may fail to correctly determine an incoming FAX call notice. For example, there is an incoming FAX call determination process of analyzing a ringing component of a calling signal CNG from a FAX transmitter at intervals of a substantially short time (e.g., 20 milliseconds), determining the calling signal CNG as an incoming call when a ringing state is detected three consecutive times, and otherwise determining the calling signal CNG as noise. Herein, ringing refers to distortion of the waveform of the signal. The above-described incoming call determination process is performed to correctly distinguish an incoming call from noise.

However, if the clock frequency of the CPU is reduced based on the threshold of the CPU usage rate or the difference in power level, for example, the above-described incoming call determination process may be completed incorrectly, failing to correctly detect the ringing state. Consequently, the incoming call determination process may fail to correctly distinguish an incoming call from noise, determining an incoming call as noise or vice versa. If the clock frequency of the CPU is controlled based on the threshold of the CPU usage rate or the difference in power level in the execution of a specific function, such as correctly detecting the incoming FAX call, the function may fail to be executed normally.

A technique according to an embodiment of the present invention described below enables normal execution of a specific function by controlling the clock frequency of a control unit such as a CPU.

A communication device, an image forming apparatus, a communication controlling method, and a program according to an embodiment of the present invention will be described in detail below with reference toFIGS. 1 to 9. The communication device may be as a part of the image forming apparatus or an optical device of the image forming apparatus.

A schematic general arrangement of the image forming apparatus according to the embodiment will be described with reference toFIG. 1.

FIG. 1is a diagram illustrating a schematic general arrangement of the image forming apparatus according to the embodiment. As illustrated inFIG. 1, an image forming apparatus10according to the embodiment is an MFP equipped with at least a FAX function. Herein, the MFP is a multifunction peripheral having at least two of a copier function, a printer function, a scanner function, and a FAX function. Specifically, the FAX function of the image forming apparatus10is realized by a FAX unit40, as illustrated inFIG. 1. With the FAX function, the FAX unit40transmits and receives data of a document, for example, via a FAX line, which is an analog line or a digital line such as integrated services digital network (ISDN), for example.

A hardware configuration of the image forming apparatus10according to the embodiment will be described with reference toFIG. 2.

FIG. 2is a diagram illustrating an example of the hardware configuration of the image forming apparatus10according to the embodiment. As illustrated inFIG. 2, the image forming apparatus10includes, for example, an operation unit20that receives an operation performed by a user, a main unit30that realizes a variety of image forming functions such as the copier function, the scanner function, and the printer function, and a facsimile unit as an example of the FAX unit40that realizes the FAX function. Herein, receiving an operation performed by a user is a concept including receiving information input through the operation performed by the user, such as a signal representing coordinate values in a screen.

The operation unit20and the main unit30are connected to each other via a dedicated communication line130to be communicable with each other. The communication line130may conform to the universal series bus (USB) standard, for example. However, the communication line130is not limited thereto, and may conform to any wired or wireless standard. Further, the main unit30and the FAX unit40are directly connected to each other via a bus to be communicable with each other. However, the main unit30and the FAX unit are not limited to this type of connection, and may be connected to each other by a dedicated connection interface (I/F). That is, the main unit30may be understood as including the FAX unit40. In the following description of the embodiment, however, it is assumed that the main unit30and the FAX unit40are separated from each other, as illustrated inFIG. 2and other drawings, for convenience of description.

The main unit30and the FAX unit40operate in accordance with an operation received by the operation unit20. Further, the main unit30is capable of communicating with an external apparatus such as a client PC and operating in accordance with an instruction received from the external apparatus.

A hardware configuration of the operation unit20will be described.

As illustrated inFIG. 2, the operation unit20includes a CPU101, a read only memory (ROM)102, a random access memory (RAM)103, a flash memory104, a connection I/F105, an operation panel106, and a system bus107.

The CPU101performs overall control of the operation of the operation unit20. The CPU101controls the operation of the entire operation unit20by executing a program stored in the ROM102or the flash memory104, for example, while using the RAM103as a work area. For example, the CPU101realizes a variety of functions, such as displaying information (e.g., an image) on the operation panel106in accordance with an input received from the user.

The ROM102is a nonvolatile memory that stores, for example, a variety of settings and a basic input/output system (BIOS) executed when the operation unit20is activated. The RAM103is a volatile memory used as the work area of the CPU101, for example. The flash memory104is a nonvolatile memory device that stores, for example, an operating system (OS), an application program, and a variety of data.

The connection I/F105is an interface for communicating with the main unit30via the communication line130.

The operation panel106is a device with an input function of receiving a variety of inputs according to operations performed by the user and a display function of displaying a variety of information, such as information according to received operations, information of the operating state of the image forming apparatus10, and information of settings, for example. The operation panel106is formed as a liquid crystal display (LCD) equipped with a touch panel function, for example. The operation panel106is not limited to the LCD, and may be formed as an organic electro-luminescence (EL) display device equipped with the touch panel function, for example. In addition to or in place of the touch panel function, the operation panel106may include an operation unit including hardware keys or a display unit including a lamp, for example.

The system bus107is a transmission line that connects the above-described components to transmit therebetween address signals, data signals, and a variety of control signals, for example.

A hardware configuration of the main unit30will be described.

As illustrated inFIG. 2, the main unit30includes a CPU111, a ROM112, a RAM113, a storage114, a memory card reader115, an engine116, a power supply117, a connection I/F118, a communication I/F119, and a system bus120.

The CPU111performs overall control of the operation of the main unit30. The CPU111controls the operation of the entire main unit30by executing a program stored in the ROM112or the storage114, for example, while using the RAM113as a work area. For example, the CPU111realizes a variety of functions such as the copier function, the scanner function, and the printer function described above. The CPU111may be replaced by a control unit called system-on-a-chip (SoC), which is an integrated circuit equipped with a CPU core and functions for controlling peripheral circuits, for example.

The ROM112is a nonvolatile memory that stores, for example, a variety of settings and a BIOS executed when the main unit30is activated. The RAM113is a volatile memory used as the work area of the CPU111, for example. The storage114is a nonvolatile memory device that stores an OS, an application program, and a variety of data, for example. The storage114is formed as a hard disk drive (HDD) or a solid state drive (SSD), for example.

The memory card reader115is a device that controls data reading, writing, and deletion on a memory card, which is an example of a removable memory medium such as a secure digital (SD) card, a mini SD card, or a micro SD card, for example.

The engine116is hardware that performs processing other than general information processing and communication to realize functions such as the copier function, the scanner function, and the printer function. The engine116includes, for example, a scanner unit that scans and reads the image of a document and a plotter unit that prints on a sheet material such as a sheet of paper. The engine116may also include a specific optional device, such as a finisher that sorts printed sheet materials or an automatic document feeder (ADF) that automatically feeds a document.

The power supply117is a device that manages supply of power to devices of the image forming apparatus10.

The connection I/F118is an interface for communicating with the operation unit20via the communication line130. The communication IN119is a network interface for connecting the main unit30to a network140, such as a local area network (LAN) or the Internet, to allow the main unit30to communicate with an external device connected to the network140.

The system bus120is a transmission line that connects the above-described components to transmit therebetween address signals, data signals, and a variety of control signals, for example.

A hardware configuration of the FAX unit40will be described.

As illustrated inFIG. 2, the FAX unit40includes a CPU121, a modem122, and a system bus123.

The CPU121performs overall control of the operation of the FAX unit40. The CPU121controls the operation of the entire FAX unit40by executing a program for the FAX unit40. The FAX unit40may include a ROM and a RAM, for example. In that case, the CPU121may execute the program for the FAX unit40stored in the ROM by using the RAM as a work area. Further, similarly to the CPU111, the CPU121may be replaced by an SoC as an integrated circuit equipped with a CPU core and functions for controlling peripheral circuits, for example.

The modem122is a device connected to the FAX line to detect an incoming call based on ringing of a received incoming call signal and transmit and receive data.

The FAX unit40includes the dedicated CPU121that executes the operation of the FAX function. However, the FAX unit40is not limited to this configuration. For example, the FAX unit40may not include the CPU121, and the CPU111included in the main unit30may control the operation of the FAX unit40based on the FAX function.

Further, the hardware configuration of the operation unit20, the main unit30, and the FAX unit40illustrated inFIG. 2is illustrative. Therefore, the operation unit20, the main unit30, and the FAX unit40are not required to include all of the components illustrated inFIG. 2, and may include other components.

A configuration of functional units of the image forming apparatus10according to the embodiment will be described with reference toFIG. 3.

FIG. 3is a diagram illustrating a configuration example of functional blocks of the image forming apparatus10according to the embodiment.

As a configuration of the functional units of the operation unit20in the image forming apparatus10, the operation unit20includes a display control unit201, a display unit202, and a storage unit203, as illustrated inFIG. 3.

The display control unit201is a functional unit that controls a display operation of the display unit202. Specifically, the display control unit201displays on the display unit202a setting screen for setting by a setting unit306of the main unit30and an operation screen serving as a user interface (UI) for the user. The display control unit201is realized by a program (e.g., a driver) executed by the CPU101illustrated inFIG. 2, for example.

The display unit202is a functional unit that displays a variety of data under the control of the display control unit201, and is realized by the display function of the operation panel106illustrated inFIG. 2.

The storage unit203is a functional unit that stores programs and a variety of data, and is realized by the RAM103and the flash memory104illustrated inFIG. 2, for example.

The display control unit201, the display unit202, and the storage unit203of the operation unit20illustrated inFIG. 3are conceptual functions, and are not limited to the illustrated configuration. For example, a plurality of functional units of the operation unit20illustrated as separated functional units inFIG. 3may be configured as a single functional unit. Further, the function of a functional unit of the operation unit20illustrated inFIG. 3may be divided into a plurality of functions to configure the functional unit as a plurality of functional units.

Further, the display control unit201of the operation unit20may be realized not by a software program but by a hardware circuit, such as a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

As a configuration of the functional units of the main unit30in the image forming apparatus10, the main unit30includes a main unit power supply control unit301, an engine control unit302, a device control unit303, a FAX unit state checking unit304, a CPU control unit305, a setting unit306, and a storage unit307, as illustrated inFIG. 3. The main unit power supply control unit301is an example of a first power supply control unit. The FAX unit state checking unit304is an example of a first determining unit. The CPU control unit305is an example of a control unit.

The main unit power supply control unit301is a functional unit that manages the power supply to devices of the image forming apparatus10by the power supply117, to thereby control the operating state of the image forming apparatus10. In the present embodiment, whether the operating state of the image forming apparatus10is the power saving state will be discussed. Hereinafter, the state in which the image forming apparatus operates in power saving mode may be referred to as the power saving state. The main unit power supply control unit301is realized by a program executed by the CPU111illustrated inFIG. 2, for example.

The engine control unit302is a functional unit that performs power control of the engine116in accordance with a command from the main unit power supply control unit301. The engine control unit302is realized by the program executed by the CPU111illustrated inFIG. 2, for example.

The device control unit303is a functional unit that performs power control of devices such as the memory card reader115in accordance with a command from the main unit power supply control unit301. The device control unit303is realized by the program executed by the CPU111illustrated inFIG. 2, for example.

The FAX unit state checking unit304is a functional unit that checks whether the power supply of the FAX unit40is turned on. The FAX unit state checking unit304notifies the main unit power supply control unit301of the checked state of the power supply of the FAX unit40. The FAX unit state checking unit304is realized by the program executed by the CPU111illustrated inFIG. 2, for example.

The CPU control unit305is a functional unit that calculates the usage rates of the CPUs111and121and controls increase or reduction in the clock frequencies of the CPUs111and121in accordance with a command from the main unit power supply control unit301. The CPU control unit305is realized by the program executed by the CPU111illustrated inFIG. 2, for example.

The usage rate calculation and the increase or reduction of the clock frequency by the CPU control unit305are not limited to the CPUs111and121, and may also apply to the CPU101of the operation unit20or control units such as SoCs having functions corresponding to these CPUs, for example. In the following description, a CPU subjected to the usage rate calculation and the increase or reduction of the clock frequency by the CPU control unit305may be simply referred to as the CPU.

The setting unit306is a functional unit that sets a variety of information specifying the operation of the image forming apparatus10. For example, the setting unit306performs setting as to whether to allow transition of the power saving state to the low-clock engine off state, as described in detail later with reference toFIG. 6. The setting unit306is realized by the program executed by the CPU111illustrated inFIG. 2, for example.

The storage unit307is a functional unit that stores a variety of information used by the image forming apparatus10. The storage unit307stores information of settings made by the setting unit306, for example. The storage unit307is realized by at least one of the RAM113and the storage114illustrated inFIG. 2.

The main unit power supply control unit301, the engine control unit302, the device control unit303, the FAX unit state checking unit304, the CPU control unit305, the setting unit306, and the storage unit307of the main unit30illustrated inFIG. 3are conceptual functions, and are not limited to the illustrated configuration. For example, a plurality of functional units of the main unit30illustrated as separate functional units inFIG. 3may be configured as a single functional unit. Further, the function of a functional unit of the main unit30illustrated inFIG. 3may be divided into a plurality of functions to configure the functional unit as a plurality of functional units.

Further, the main unit power supply control unit301, the engine control unit302, the device control unit303, the FAX unit state checking unit304, the CPU control unit305, and the setting unit306of the main unit30may be realized not by a software program but by a hardware circuit, such as an FPGA or an ASIC.

As a configuration of the functional units of the FAX unit40in the image forming apparatus10, the FAX unit40includes a FAX unit power supply control unit401, a ringing detecting unit402, and a ringing determining unit403, as illustrated inFIG. 3. The FAX unit power supply control unit401is an example of a second power supply control unit. The ringing detecting unit402is an example of a detecting unit. The ringing determining unit403is an example of a second determining unit.

The FAX unit power supply control unit401is a functional unit that performs power control of the FAX unit40, and is realized by a program executed by the CPU121illustrated inFIG. 2, for example.

The ringing detecting unit402is a functional unit that detects whether the ringing of the incoming call signal (e.g., the calling signal CNG) has been received by the modem122of the FAX unit40regardless of whether the power supply of the FAX unit40is on or off. The ringing detecting unit402transmits the detected ringing to the FAX unit power supply control unit401. The ringing detecting unit402is realized by the program executed by the CPU121illustrated inFIG. 2, for example.

The ringing determining unit403is a functional unit that determines whether the ringing detected by the ringing detecting unit402represents an incoming call based on the FAX function or noise. If having determined that the ringing represents an incoming call, the ringing determining unit403transmits a return request to the main unit30to return the image forming apparatus10from the power saving state. The ringing determining unit403is realized by the program executed by the CPU121illustrated inFIG. 2, for example.

The FAX unit power supply control unit401, the ringing detecting unit402, and the ringing determining unit403of the FAX unit40illustrated inFIG. 3are conceptual functions, and are not limited to the illustrated configuration. For example, a plurality of functional units of the FAX unit40illustrated as separate functional units inFIG. 3may be configured as a single functional unit. Further, the function of a functional unit of the FAX unit40illustrated inFIG. 3may be divided into a plurality of functions to configure the functional unit as a plurality of functional units.

Further, the FAX unit power supply control unit401, the ringing detecting unit402, and the ringing determining unit403of the FAX unit40may be realized not by a software program but by a hardware circuit, such as an SoC, an FPGA, or an ASIC.

The transition of the power saving state of the image forming apparatus10according to the embodiment will be described with reference toFIG. 4.

FIG. 4is a diagram illustrating an example of the transition of the power saving state of the image forming apparatus10according to the embodiment. InFIG. 4, respective power saving states are assigned with reference numerals for convenience of description.

As illustrated inFIG. 4, operating states taken on by the image forming apparatus10according to the embodiment as power saving states include an activated state50and a main power off state60.

The activated state50is an operating state in which at least the CPU is operating, and at least one of the above-described units is ready to operate. The main power off state60is an operating state in which the operation of the CPU is stopped, and none of the above-described units is ready to operate. In the main power off state60, it is possible to pull out a power plug safely. In the main power off state60, power consumption is lower than in the other operating states. To use the units in the main power off state60, however, it takes a few minutes before the units become ready to be activated after a main power button is pressed.

Further, as illustrated inFIG. 4, the activated state50as one of the power saving states of the image forming apparatus10includes a standby state51and an engine off state55. The standby state51is an example of a first power state, and the engine off state55is an example of a second power state.

The standby state51is an operating state in which the respective units (i.e., devices) of the image forming apparatus10are activated, and the power consumption is higher than in the other operating states. That is, all functions of the image forming apparatus10are usable in the standby state51. In the example illustrated inFIG. 4, when the power saving state of the image forming apparatus10is the standby state51, the CPU (or a controller equipped with the CPU or the SoC, for example) is operating, and the LCD of the operation panel106of the operation unit20is on. Further, when the power saving state of the image forming apparatus10is the standby state51, the power supply of the engine116(e.g., the scanner unit and the plotter unit) is on, the communication function of the communication I/F119is enabled, and the power supply of the devices (e.g., the memory card reader115) is on. As illustrated inFIG. 4, the image forming apparatus10transitions between the standby state51and the main power off state60when a predetermined condition is met, such as when a predetermined operation is performed on the operation panel106by the user.

As illustrated inFIG. 4, the image forming apparatus10transitions between the standby state51and the engine off state55when a predetermined condition is met, such as when a predetermined operation is performed on the operation panel106by the user, or when a condition related to timer setting or the state of the image forming apparatus10is met.

The engine off state55is an operating state in which the power supply of the engine116(e.g., the scanner unit and the plotter unit) is off, and the CPU (or the controller) is operating and thus executing the program. Further, as illustrated inFIG. 4, the engine off state55as one of the power saving states of the image forming apparatus10includes a regular engine off state56, a high-clock engine off state57, and a low-clock engine off state58.

The regular engine off state56is an operating state in which the power supply of the engine116(e.g., the scanner unit and the plotter unit) is off, and the power supply of the devices (e.g., the memory card reader115) is on. When the power saving state of the image forming apparatus10transitions from the engine off state55to the standby state51, the image forming apparatus10is in the regular engine off state56as the power saving state. That is, as illustrated inFIG. 4, the image forming apparatus10transitions between the regular engine off state56and the standby state51when a predetermined condition is met, such as when a predetermined operation is performed on the operation panel106by the user, or when a condition related to timer setting or the state of the image forming apparatus10is met. In the example illustrated inFIG. 4, when the power saving state of the image forming apparatus10is the regular engine off state56, the CPU (or the controller) is operating, and the LCD of the operation panel106of the operation unit20is on when in use and off or in a sleep state when not in use. Further, in the regular engine off state56, the power supply of the engine116(e.g., the scanner unit and the plotter unit) is off, the communication function of the communication I/F119is enabled, and the power supply of the devices (e.g., the memory card reader115) is on.

The high-clock engine off state57is an operating state in which, when the image forming apparatus10in the low-clock engine off state58does not operate normally or has or may have a trouble due to slowdown of processing, for example, the CPU control unit305temporarily increases the clock frequency of the CPU to restore normal operation. In the example illustrated inFIG. 4, when the power saving state of the image forming apparatus10is the high-clock engine off state57, the CPU (or the controller) is operating at a clock frequency higher than that in the low-clock engine off state58, and the LCD of the operation panel106of the operation unit20is on when in use and off or in a sleep state when not in use. Further, in the high-clock engine off state57, the power supply of the engine116(e.g., the scanner unit and the plotter unit) is off, the communication function of the communication I/F119is enabled, and the power supply of the devices (e.g., the memory card reader115) is off.

For example, when the image forming apparatus10is accessed by an external device in the low-clock engine off state58in which the clock frequency of the CPU is reduced, the usage rate of the CPU is increased, increasing the time for the access process. When the usage rate of the CPU exceeds a predetermined value in this case, the image forming apparatus10is temporarily transitioned from the low-clock engine off state58to the high-clock engine off state57. This transition operation of the image forming apparatus10will be described later with reference toFIG. 8.

Further, when the ringing is detected in the low-clock engine off state58of the image forming apparatus10, in which the clock frequency of the CPU is reduced, the determination of whether the ringing represents an incoming call or noise may fail to be correctly made owing to the low clock frequency of the CPU and thus an elongated processing time. In this case, the image forming apparatus10is temporarily transitioned from the low-clock engine off state58to the high-clock engine off state57. This transition operation of the image forming apparatus10will be described later with reference toFIGS. 7A and 71B.

The power consumption is higher in the high-clock engine off state57than in the low-clock engine off state58. Therefore, it is desirable to return the image forming apparatus10to the low-clock engine off state58when the condition for transitioning the image forming apparatus10to the low-clock engine off state58is met. Thus, the high-clock engine off state57is not a steady operating state but a temporary operating state.

The low-clock engine off state58is an operating state in which the clock frequency of the CPU is reduced and the unnecessary power supply of the devices is turned off to reduce the power consumption as compared with in the regular engine off state56. That is, in the low-clock engine off state58, the clock frequency of the CPU is reduced, increasing the time for the processes of the image forming apparatus10and facilitating the increase in the usage rate of the CPU. In the low-clock engine off state58, therefore, the power supply of the devices (e.g., the memory card reader115) is also turned off, preventing access to the memory card such as the micro SD card. In the example illustrated inFIG. 4, when the power saving state of the image forming apparatus10is the low-clock engine off state58, the CPU (or the controller) is operating at a clock frequency lower than those in the regular engine off state56and the high-clock engine off state57, and the LCD of the operation panel106of the operation unit20is on when in use and off or in a sleep state when not in use. Further, in the low-clock engine off state58, the power supply of the engine116(e.g., the scanner unit and the plotter unit) is off, the communication function of the communication I/F119is enabled, and the power supply of the devices (e.g., the memory card reader115) is off. Herein, the above-described controller is, for example, a unit such as an electronic circuit board integrating the CPU111, the ROM112, the RAM113, the storage114, the memory card reader115, the connection I/F118, and the communication I/F119of the main unit30inFIG. 2.

As illustrated inFIG. 4, the image forming apparatus10transitions between the regular engine off state56and the low-clock engine off state58when a predetermined condition is met. Further, the image forming apparatus10transitions between the high-clock engine off state57and the low-clock engine off state58when a predetermined condition is met. Further, the image forming apparatus10transitions from the high-clock engine off state57to the regular engine off state56when a predetermined condition is met. Specific examples of these transition operations between the regular engine off state56, the high-clock engine off state57, and the low-clock engine off state58will be described in detail below with reference toFIGS. 5 to 9.

The image forming apparatus10is assumed to take on one of the power saving states illustrated inFIG. 4, i.e., the main power off state60, the standby state51, the regular engine off state56, the high-clock engine off state57, and the low-clock engine off state58, and not to simultaneously take on two or more of these power saving states.

Further, the power saving states illustrated inFIG. 4are illustrative of the operating states of the image forming apparatus10, and the image forming apparatus10is not limited to these operating states.

With reference toFIGS. 5 and 6, a description will be given of an example of the transition operation in which the image forming apparatus10of the embodiment transitions from the regular engine off state56to the low-clock engine off state58.

FIG. 5is a sequence diagram illustrating an example of the operation in which the image forming apparatus10of the embodiment transitions to the low-clock engine off state58.FIG. 6is a diagram illustrating an example of a screen for setting as to whether to allow the transition of the image forming apparatus10of the embodiment to the low-clock engine off state58.

When a predetermined condition is met, the main unit power supply control unit301of the main unit30transitions the power saving state of the image forming apparatus10to the regular engine off state56(step S11).

After the transition to the regular engine off state56, the main unit power supply control unit301transmits an engine power-off request to the engine control unit302to turn off the power supply of the engine116(e.g., the plotter unit and the scanner unit) (step S12).

In response to the engine power-off request from the main unit power supply control unit301, the engine control unit302turns off the power supply of the engine116(step S13).

After the transition to the regular engine off state56, the main unit power supply control unit301transmits a FAX power-off request to the FAX unit power supply control unit401of the FAX unit40to turn off the power supply of the FAX unit40(step S14).

In response to the FAX power-off request from the main unit power supply control unit301, the FAX unit power supply control unit401turns off the power supply of the FAX unit40(step S15).

When a predetermined condition is met after the lapse of a predetermined time (e.g., five seconds) since the transition of the power saving state of the image forming apparatus10to the regular engine off state56, the main unit power supply control unit301transitions the power saving state of the image forming apparatus10to the low-clock engine off state58. Herein, the predetermined condition is when the memory card reader115is not accessing the memory card and the power supply of the operation unit20and the power supply of the FAX unit40are off, for example. For instance, when the memory card reader115is performing a process of accessing the memory card, it is not desirable to transition the image forming apparatus10to the low-clock engine off state58, in which the access process may slow down. Further, when the power supply of the FAX unit40is on, it is desirable not to transition the image forming apparatus10to the low-clock engine off state58to correctly determine whether the ringing represents an incoming call.

The above-described predetermined condition may also include when a setting allowing the transition of the image forming apparatus10to the low-clock engine off state58is made by the setting unit306on the setting screen displayed on the operation panel106of the operation unit20as illustrated inFIG. 6, for example.FIG. 6illustrates an example of the setting screen, in which the setting allowing the transition to the low-clock engine off state58is selected. In the low-clock engine off state58, the clock frequency of the CPU is reduced, reducing the power consumption, but at the same time slowing down the processes of the image forming apparatus10as compared with those in the regular engine off state56, for example. For possible users who prefer to avoid such a situation, therefore, a setting screen such as that illustrated inFIG. 6may be provided to allow the users to perform the setting as to whether to allow the transition to the low-clock engine off state58. In the transition process from the regular engine off state56to the low-clock engine off state58, the main unit power supply control unit301may refer to the information of settings made by the setting unit306on the setting screen illustrated inFIG. 6. Then, if a setting disallowing the transition is made, the main unit power supply control unit301may maintain the image forming apparatus10in the regular engine off state56.

Then, after the transition to the low-clock engine off state58, the main unit power supply control unit301transmits a device power-off request to the device control unit303to turn off the power supply of the devices (e.g., the memory card reader115) (step S16).

In response to the device power-off request from the main unit power supply control unit301, the device control unit303turns off the power supply of the devices (step S17).

After the transition to the low-clock engine off state58, the main unit power supply control unit301transmits a clock-down command to the CPU control unit305to reduce the clock frequency of the CPU (step S18).

In response to the clock-down command from the main unit power supply control unit301, the CPU control unit305reduces the clock frequency of the CPU (step S19). Herein, methods of reducing of the clock frequency of the CPU include reducing the clock frequency by a predetermined value to a clock frequency equal to or greater than a predetermined minimum value, and reducing the clock frequency by a predetermined ratio to the current clock frequency, for example. For instance, the CPU control unit305reduces each of the clock frequencies of the CPUs111and121from 800 megahertz (MHz) to 20 MHz. These clock frequencies are illustrative, and may be changed as appropriate in accordance with the specifications of an employed system. Further, the clock frequency of the CPU111and the clock frequency of the CPU121may be individually changed.

With steps S11to S19described above, the image forming apparatus10transitions from the regular engine off state56to the low-clock engine off state58.

With reference toFIGS. 7A and 71B, a description will be given of an example of the transition operation in which the image forming apparatus10of the embodiment transitions from the low-clock engine off state58to the high-clock engine off state57to determine whether the ringing represents an incoming call.

FIGS. 7A and 71Bare a sequence diagram illustrating an example of the operation in which the image forming apparatus10of the embodiment transitions from the low-clock engine off state58to the high-clock engine off state57in response to the incoming call signal.

It is assumed here that the image forming apparatus10is in the low-clock engine off state58. If the ringing detecting unit402of the FAX unit40detects the receipt of the incoming call signal via the FAX line in the low-clock engine off state58, the ringing detecting unit402transmits the incoming call signal to the FAX unit power supply control unit401(step S31). The incoming call signal is an example of an input signal to be detected, and may be a calling signal CNG having a frequency of 1100 Hz, for example.

In response to the incoming call signal from the ringing detecting unit402, the FAX unit power supply control unit401turns on the power supply of the FAX unit40(step S32).

After turning on the power supply of the FAX unit40, the FAX unit power supply control unit401transmits the received incoming call signal to the ringing determining unit403(step S33).

The ringing determining unit403executes incoming call determination of determining whether the received incoming call signal represents an incoming call or noise (step S34). The incoming call determination is an example of a specific function related to communication. In this case, the power supply of the FAX unit40is on, and the clock frequencies of the CPUs111and121are increased at step S40described later. The incoming call determination is therefore executed with the clock frequencies of the CPUs111and121increased. That is, the incoming call determination on the incoming call signal at steps S31to S34inFIGS. 7A and 71Band a later-described process of increasing the clock frequencies of the CPUs111and121at steps S35to S40inFIGS. 7A and 71Bare executed in parallel, although the process of increasing the clock frequencies of the CPUs111and121at steps S35to S40is illustrated after the incoming call determination at steps S31to S34in the sequence ofFIGS. 7A and 71Bfor convenience of illustration. In the present embodiment, each of the clock frequencies of the two CPUs111and121is increased as the process of increasing the clock frequency of the CPU, as described above. In the following, increasing (or reducing) each of the clock frequencies of the CPUs111and121may be simply described as “increasing (or reducing) the clock frequency of the CPU.” Alternatively, the clock frequency of the CPU111and the clock frequency of the CPU121may be individually controlled to change (i.e., increase) the clock frequency of one of the CPUs111and121, which is desired to be changed (i.e., increased).

The above-described processes of steps S31to S34are executed each time the ringing detecting unit402detects the receipt of the incoming call signal. If the power supply of the FAX unit40is already on, however, the process of step S32is skipped.

When the image forming apparatus10is in the low-clock engine off state58, the main unit power supply control unit301transmits a FAX state check request to the FAX unit state checking unit304at intervals of a predetermined time (e.g., every second) to check the state of the power supply of the FAX unit40(step S35).

The FAX unit state checking unit304transmits the FAX state check request received from the main unit power supply control unit301to the FAX unit power supply control unit401of the FAX unit40(step S36).

In response to the FAX state check request, the FAX unit power supply control unit401checks whether the power supply of the FAX unit40is on or off, and transmits FAX state information including the check result to the FAX unit state checking unit304of the main unit30(step S37).

The FAX unit state checking unit304transmits the FAX state information received from the FAX unit power supply control unit401to the main unit power supply control unit301(step S38).

If the FAX state information received from the FAX unit state checking unit304indicates that the power supply of the FAX unit40is on, the main unit power supply control unit301transmits a clock-up command to the CPU control unit305to increase the clock frequency of the CPU (step S39).

In response to the clock-up command from the main unit power supply control unit301, the CPU control unit305increases the clock frequency of the CPU (step S40). Herein, the methods of increasing the clock frequency of the CPU include, for example, increasing the clock frequency by a predetermined value, increasing the clock frequency by a predetermined ratio to the current clock frequency, and increasing the clock frequency based on the difference or ratio between the frequency of the received incoming call signal and the clock frequency. When the power supply of the FAX unit40is turned on and the clock frequency of the CPU is increased, as described above, the power saving state of the image forming apparatus10transitions from the low-clock engine off state58to the high-clock engine off state57. For instance, the CPU control unit305increases each of the clock frequencies of the CPUs111and121to 800 MHz from 20 MHz. These clock frequencies are illustrative, and may be changed as appropriate in accordance with the specifications of the employed system. Further, the clock frequency of the CPU111and the clock frequency of the CPU121may be individually changed, as described above. When increasing the clock frequency, the main unit power supply control unit301transitions the image forming apparatus10from the low-clock engine off state58to the high-clock engine off state57, as described above. At this stage, however, the main unit power supply control unit301maintains the image forming apparatus10in the engine off state55, without transitioning the image forming apparatus10to the standby state51, as illustrated inFIG. 4.

When the image forming apparatus10is in the low-clock engine off state58, the above-described processes of steps S35to S40are repeated at intervals of a predetermined time (e.g., every second).

When the image forming apparatus10transitions to the high-clock engine off state57, and if it is determined from the above-described incoming call determination by the ringing determining unit403at step S34that the incoming call signal represents an incoming call, the image forming apparatus10transitions (i.e., returns) to the standby state51to perform a FAX receiving process based on the FAX function of the FAX unit40(step S41). This operation of transitioning to the standby state51will be described in detail later with reference to another sequence illustrated inFIG. 9.

When the image forming apparatus10transitions to the high-clock engine off state57, and if it is determined from the above-described incoming call determination by the ringing determining unit403at step S34that the incoming call signal represents noise, the ringing determining unit403transmits a determination result indicating that the incoming call signal represents noise to the FAX unit power supply control unit401(step S42).

If the FAX unit power supply control unit401determines that the ringing state has ended based on the determination result from the ringing determining unit403indicating that the incoming call signal represents noise, for example, the FAX unit power supply control unit401turns off the power supply of the FAX unit40(step S43).

After the lapse of a predetermined time (e.g., five seconds) since the transition of the image forming apparatus10to the high-clock engine off state57, the main unit power supply control unit301transmits the FAX state check request to the FAX unit state checking unit304at intervals of a predetermined time (e.g., every second) to check the state of the power supply of the FAX unit40(step S44).

The FAX unit state checking unit304transmits the FAX state check request received from the main unit power supply control unit301to the FAX unit power supply control unit401of the FAX unit40(step S45).

In response to the FAX state check request, the FAX unit power supply control unit401checks whether the power supply of the FAX unit40is on or off, and transmits the FAX state information including the check result to the FAX unit state checking unit304of the main unit30(step S46).

The FAX unit state checking unit304transmits the FAX state information received from the FAX unit power supply control unit401to the main unit power supply control unit301(step S47).

If the FAX state information received from the FAX unit state checking unit304indicates that the power supply of the FAX unit40is off, the main unit power supply control unit301transmits the clock-down command to the CPU control unit305to reduce the clock frequency of the CPU (step S48).

In response to the clock-down command from the main unit power supply control unit301, the CPU control unit305reduces the clock frequency of the CPU (step S49). When the power supply of the FAX unit40is turned off and the clock frequency of the CPU is reduced, as described above, the power saving state of the image forming apparatus10transitions from the high-clock engine off state57to the low-clock engine off state58.

When the image forming apparatus10is in the high-clock engine off state57, the above-described processes of steps S44to S49are repeated at intervals of a predetermined time (e.g., every second).

With steps S31to S49described above, the image forming apparatus10transitions from the low-clock engine off state58to the high-clock engine off state57to perform the incoming call determination.

As described above, when the receipt of the incoming call signal is detected in the low-clock engine off state58of the image forming apparatus10, the power supply of the FAX unit40is turned on, and the clock frequency of the CPU is increased to transition the image forming apparatus10to the high-clock engine off state57. Even if the incoming call signal is received in the low-clock engine off state58, therefore, the increased clock frequency of the CPU enables normal execution of a incoming call determination function of determining whether the incoming call signal represents an incoming call or noise.

With reference toFIG. 8, a description will be given of an example of the transition operation in which the image forming apparatus10of the embodiment transitions from the low-clock engine off state58to the high-clock engine off state57to normally execute the incoming call determination, which is an example of the specific function.

FIG. 8is a sequence diagram illustrating an example of the operation in which the image forming apparatus10of the embodiment transitions from the low-clock engine off state58to the high-clock engine off state57based on the usage rate of the CPU. Herein, the image forming apparatus10is assumed to be in the low-clock engine off state58. When the image forming apparatus10is in the low-clock engine off state58, the CPU control unit305(i.e., an example of the control unit) of the main unit30checks (i.e., calculates) the usage rate of the CPU (step S51).

If the usage rate of the CPU calculated by the CPU control unit305continues to be equal to or greater than a first threshold having a predetermined value (e.g., 90%) for a predetermined time (e.g., three seconds), the CPU control unit305increases the clock frequency of the CPU by employing one of the above-mentioned exemplary methods (step S52). With the clock frequency of the CPU thus increased, the power saving state of the image forming apparatus10transitions from the low-clock engine off state58to the high-clock engine off state57.

The thus temporarily increased clock frequency of the CPU increases the throughput of the CPU. Therefore, the incoming call determination as a factor increasing the usage rate of the CPU is normally executed, and the usage rate of the CPU is reduced.

The CPU control unit305notifies the main unit power supply control unit301of the increase in the clock frequency of the CPU (step S53).

If a predetermined condition is met after the lapse of a predetermined time (e.g., five seconds) since the transition of the power saving state of the image forming apparatus10to the high-clock engine off state57, the main unit power supply control unit301transmits the clock-down command to the CPU control unit305to reduce the clock frequency of the CPU (step S54). Herein, the predetermined condition includes, for example, when the usage rate of the CPU is reduced to or below a second threshold having a predetermined value (e.g., 50%) owing to normal execution of the incoming call determination as a factor increasing the usage rate of the CPU.

In response to the clock-down command from the main unit power supply control unit301, the CPU control unit305reduces the clock frequency of the CPU (step S55). With the clock frequency of the CPU thus reduced, the power saving state of the image forming apparatus10transitions from the high-clock engine off state57to the low-clock engine off state58.

With steps S51to S55described above, the image forming apparatus10transitions from the low-clock engine off state58to the high-clock engine off state57to normally execute the incoming call determination.

As described above, if the usage rate of the CPU continues to be equal to or greater than a predetermined value for a predetermined time in the low-clock engine off state58of the image forming apparatus10, the clock frequency of the CPU is increased to transition the image forming apparatus10to the high-clock engine off state57. Thereby, the throughput of the CPU is increased, enabling normal execution of the incoming call determination and a reduction in the usage rate of the CPU.

With reference toFIG. 9, a description will be given of an example of the transition operation in which the image forming apparatus10of the embodiment transitions from the low-clock engine off state58to the standby state51.

FIG. 9is a sequence diagram illustrating an example of the operation in which the image forming apparatus10of the embodiment transitions from the low-clock engine off state58to the standby state51. The image forming apparatus10is assumed to be in the low-clock engine off state58at the beginning of the sequence inFIG. 9.

It is assumed here that a user70performs an input operation on the operation panel106of the operation unit20as a condition for returning the image forming apparatus10to the standby state51(step S71).

If the operation unit20is in the sleep state, for example, the input operation performed on the operation panel106of the operation unit20by the user70brings the operation unit20back to the operable state. Then, the display control unit201of the operation unit20detects the input operation performed by the user70, and transmits a return request to the main unit power supply control unit301of the main unit30to return the power saving state of the image forming apparatus10to the standby state51from the low-clock engine off state58(step S72). In the present example, the display control unit201detects the input operation. However, the configuration is not limited thereto, and a control unit dedicated to operations may detect the input operation.

Alternatively, if it is determined in the incoming call determination by the ringing determining unit403at step S34inFIG. 7Bthat the incoming call signal represents an incoming call as a condition for returning the image forming apparatus10to the standby state51(step S73), the ringing determining unit403transmits the return request to the main unit power supply control unit301of the main unit30to return the power saving state of the image forming apparatus10to the standby state51from the low-clock engine off state58(step S74).

In response to the return request from the operation unit20or the FAX unit40, the main unit power supply control unit301of the main unit30transmits the clock-up command to the CPU control unit305to increase the clock frequency of the CPU (step S75).

In response to the clock-up command from the main unit power supply control unit301, the CPU control unit305increases the clock frequency of the CPU by employing one of the above-mentioned exemplary methods (step S76).

Further, in response to the return request from the operation unit20or the FAX unit40, the main unit power supply control unit301transmits a device power-on request to the device control unit303to turn on the power supply of the devices (e.g., the memory card reader115) (step S77).

In response to the device power-on request from the main unit power supply control unit301, the device control unit303turns on the power supply of the devices (step S78). When the clock frequency of the CPU is increased and the power supply of the devices is turned on, as described above, the power saving state of the image forming apparatus10transitions to the regular engine off state56from the low-clock engine off state58.

After the image forming apparatus10transitions to the regular engine off state56, the main unit power supply control unit301transmits an engine power-on request to the engine control unit302to turn on the power supply of the engine116(e.g., the plotter unit and the scanner unit) (step S79).

In response to the engine power-on request from the main unit power supply control unit301, the engine control unit302turns on the power supply of the engine116(step S80). With the power supply of the engine116thus turned on in the regular engine off state56, the power saving state of the image forming apparatus10transitions from the regular engine off state56to the standby state51.

With steps S71to S80described above, the image forming apparatus10transitions from the low-clock engine off state58to the standby state51.

If the return request is issued from the operation unit20or the FAX unit40in the high-clock engine off state57, processes similar to those inFIG. 9may be performed. In the high-clock engine off state57, however, the CPU has a high clock frequency, and thus the processes of steps S75and S76inFIG. 9may be omitted.

As described above, when not executing the incoming call determination, which increases a processing load on the CPU, the image forming apparatus10of the embodiment is placed in the low-clock engine off state58, in which the clock frequency of the CPU is reduced. Then, when executing the incoming call determination, the image forming apparatus10is transitioned to the high-clock engine off state57to increase the clock frequency of the CPU. Thereby, the throughput of the CPU is increased, enabling normal execution of the incoming call determination and a reduction in the usage rate of the CPU.

Particularly in the incoming call determination process on the incoming call signal based on the FAX function, if the receipt of the incoming call signal is detected in the low-clock engine off state58of the image forming apparatus10, the power supply of the FAX unit is turned on, and the clock frequency of the CPU is increased to transition the image forming apparatus10to the high-clock engine off state57. Even if the incoming call signal is received in the low-clock engine off state58, therefore, the increased clock frequency of the CPU enables normal execution of the incoming call determination function of determining whether the incoming call signal represents an incoming call or noise.

Further, when the incoming call determination process is completed in the high-clock engine off state57, the image forming apparatus10is returned to the low-clock engine off state58. Accordingly, the power consumption of the image forming apparatus10is reduced.

The image forming apparatus10described above is an MFP with at least the FAX function. However, the image forming apparatus10is not limited thereto. For example, the image forming apparatus10may be an MFP including a variety of communication devices involving clock control in the execution of a specific function related to communication and a unit that executes a specific function other than the FAX-related function. The present embodiment is applicable to any communication device including a communication circuit functioning as an executing unit that executes a specific function related to communication, such as a FAX unit, for example.

Further, if at least one of the functional units of the image forming apparatus10of the above-described embodiment is realized by execution of a program, the program is provided as previously stored in a ROM, for example. Further, the program executed in the image forming apparatus10of the embodiment may be provided as recorded on a computer-readable recording medium, such as a compact disc (CD)-ROM, a flexible disk (FD), a CD-recordable (CD-R), or a digital versatile disc (DVD), in the form of an installable or executable file. Further, the program executed in the image forming apparatus10of the embodiment may be stored in a computer connected to a network such as the Internet, and may be provided as downloaded from the computer via the network. Further, the program executed in the image forming apparatus10of the embodiment may be provided or distributed via the network such as the Internet. Further, the program executed in the image forming apparatus10of the embodiment is configured as a module including at least one of the above-described functional units. The functional units are loaded on and generated in main memory devices when the CPUs as actual hardware read and execute the programs from the above-described memory devices (e.g., the flash memory104and the storage114).

Each of the functions of the described embodiments may be implemented by one or more processing circuits or circuitry. Processing circuitry includes a programmed processor, as a processor includes circuitry. A processing circuit also includes devices such as an application specific integrated circuit (ASIC), digital signal processor (DSP), field programmable gate array (FPGA), and conventional circuit components arranged to perform the recited functions. Further, the above-described steps are not limited to the order disclosed herein.