JP2008287312A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sharply reduce the power consumption of a main memory, CPU and a printing section in an image forming apparatus. <P>SOLUTION: If the time of idle state of an internal bus 4 exceeds a threshold value, the device makes a main memory 8 into a self refresh mode and into a pause mode with smallest power consumption by stopping electric power supply to a CPU 5 and a plotter 7. When receiving the data to be printed by the plotter 7, the device switches to a normal mode to operate all circuits. When receiving the data to be processed by the CPU 5 though printing by the plotter 7 is not required, the device is made into an energy saving mode to operate the CPU 5 and the main memory 8 while stopping the plotter 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that shifts to a sleep mode when an idle time of an internal bus exceeds a threshold value and significantly reduces power consumption during standby.

  2. Description of the Related Art Conventionally, energy saving of image forming apparatuses such as printers, facsimiles, copiers, and multifunction machines has been performed. By shutting down power supply to a part of the image forming apparatus, power consumption during standby can be greatly reduced. In a printer using a RAM having a power saving mode, the RAM is set to the power saving mode when there is no data for image creation for a certain period of time. When the image creation data is received, the power saving mode returns to the normal operation mode. There is also a method of stopping the clock to enter the low power mode. Below are some examples of prior art related to this.

  The “image forming apparatus” disclosed in Patent Document 1 reduces standby power while improving the function of a printer controller. The printer controller converts print information transmitted from a host PC or the like into output image data and outputs it to the printer. Switch the power supply to the printer in energy saving mode and normal operation mode. In the controller, the power supply line to the circuit element is divided into a plurality of systems, and each system is selectively turned ON / OFF.

  The “memory control circuit” disclosed in Patent Document 2 reduces the power consumption of the printer without affecting the performance of the printer. The RAM has a power saving mode and a normal operation mode. The memory control circuit receives a request for the RAM from the CPU, the I / O control circuit, and the image processing circuit. Based on the request, it controls the writing and reading of data to and from the RAM. In the memory control circuit, a refresh command for causing the RAM to perform a refresh process is generated at a predetermined interval and output to the RAM. When the RAM is in the normal operation mode, the time from when a request to the RAM or a refresh command is generated from the I / O control circuit, CPU, or image processing circuit is measured. When the measured time has passed a predetermined time, the storage device is switched from the normal operation mode to the power saving mode.

  The “image forming apparatus” disclosed in Patent Document 3 is configured so that even when returning from the energy saving mode to the normal mode, each process can be performed without delay so that it can be seen from the network side during normal operation. is there. The main CPU controls the entire system. The sub CPU controls a preset control in the system. The network control device has a normal mode and an energy saving mode. The return factor detection means detects a return factor packet for returning from the normal mode to the energy saving mode. The sub CPU processes the received packet until the return factor packet is detected. After detecting the return factor packet, the main CPU processes packets received after the return factor packet.

  The “image forming apparatus” disclosed in Patent Document 4 does not require an application for energy saving control on the host side, and can obtain a further energy saving effect. The main CPU controls on / off of the function of the network filter. When the system is in a ready state after the power is turned on, the packet type filter (TCP header filter) function for discriminating a predetermined flag included in the TCP header of the IP packet is set to an off state. In the energy saving mode, set it to the on state. When shifting from the energy saving mode to the ready state, it is set to the off state.

  The “memory control device” disclosed in Patent Document 5 efficiently performs self-refresh of a synchronous DRAM to reduce power consumption. The command of the memory access arbitration circuit is stored in the first buffer. A command output from the first buffer is stored in the second buffer. The first control circuit controls data transmission / reception with the memory based on the second buffer. The second control circuit compares the commands (addresses) stored in the first and second buffers and selects one of them.

The “information processing apparatus” proposed in Patent Document 6 can respond to a packet with respect to a network even when the power saving mode is maintained. When receiving an address resolution request addressed to the own device during the power saving mode, the packet filter unit notifies the power control unit. The power control unit maintains the power saving mode, creates a response packet in the packet processing unit, and returns the response packet to the network.
JP 2001-328313 A JP 2004-287530 A JP 2005-267100 A JP 2005-269103 A JP 2006-164099 Japanese Patent Application No. 2007-033262 Specification

  However, the conventional energy saving mode has the following problems. If the power supply to the controller with the network I / F is cut off, the MFP will not be connected to the network. Therefore, the power must be supplied to the controller even when saving energy, and the MFP is put into the energy saving mode. The whole device does not save energy. In the memory that enters the energy saving mode when there is no access for a certain period of time and returns from the energy saving mode when the access is received, even if the memory is saved in the refresh mode, the CPU and the print engine are not energy saving. Even if only the sub CPU operates at the time of energy saving, power is supplied to the entire area of the ASIC equipped with the sub CPU, so there is leakage current even if the clock is stopped. If the ASIC is miniaturized by a 90nm process, etc., the leakage current cannot be ignored and the energy saving effect is lost.

  An object of the present invention is to solve the above-mentioned conventional problems and reduce power consumption of not only a memory but also a CPU and a printing unit in an electronic apparatus such as an image processing apparatus.

  In order to solve the above problems, in the present invention, an electronic device detects that an internal bus to which a CPU, a main memory, and a data input / output unit are connected, and an idle time of the internal bus exceeds a threshold value. Bus monitoring means that outputs a bus empty signal, and the power supply state according to the bus empty signal, all circuits including the CPU and main memory except the minimum necessary circuit including a part of the data input / output unit And an energy saving management unit that switches to a sleep mode for setting the power supply to a minimum. The energy saving management unit includes means for instructing the memory control unit to output a self-refresh command to the main memory, and means for stopping supply of power or clock to the CPU.

  The data input unit is provided with means for notifying the energy saving management unit of a request to return to the normal operation mode when data to be output processed is received. The energy saving management unit receives the CPU, main memory, and data in response to the return request. Means for switching the input unit to a normal operation mode is provided. The data input unit includes means for notifying the energy saving management unit of a request for transition to the energy saving mode in which the CPU and the main memory operate when data to be processed by the CPU is received in the sleep mode state. And a means for switching the CPU and the main memory to the normal operation mode in response to the transition request.

  In addition, the image forming apparatus includes an internal bus in which a CPU, a main memory, and a data input / output unit are connected, an image printing unit that processes data received by the data input / output unit and outputs an image, and an internal bus Except for the bus monitoring means that detects that the idle time of the bus exceeds the threshold and outputs a bus empty signal, and the necessary minimum circuit including a part of the data input / output unit according to the bus empty signal The configuration includes an energy saving management unit that switches to a sleep mode that minimizes power supply to all circuits including the CPU and main memory.

  The data input unit includes means for notifying the energy saving management unit of a request to return to the normal operation mode when data to be processed by the image printing unit is received. Means for switching to a normal operation mode. The data input unit has means to notify the energy saving management unit of a CPU restoration request when data that does not require processing by the image printing unit but requires processing by the CPU is received. Accordingly, there is provided means for switching the CPU and the main memory to the normal operation mode while the power supply to the image printing unit is stopped.

  With the above configuration, the power consumption of the electronic device can be greatly reduced by switching to the sleep mode when the internal bus has been idle for a long time.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to FIGS. 1 and 2. FIG.

  In the first embodiment of the present invention, when the idle time of the internal bus to which the CPU, the main memory, and the data input / output unit are connected exceeds a threshold value, the power supply to all circuits except the minimum necessary circuits is minimized. Switch to the sleep mode to limit to the normal operation mode when print data is received, and to the energy saving mode where the CPU and main memory operate when data to be processed by the CPU is received during the sleep mode It is a printer to switch.

  FIG. 1 is a functional block diagram of the printer according to the first embodiment of the present invention and a state transition diagram regarding the operation state of the printer. In FIG. 1, a controller board 1 is a circuit part that controls the printer. The ASIC 2 is a central part of control including the CPU 5. The energy saving management unit 3 is means for managing the power supply of the printer. The internal bus 4 is a common signal bus that connects circuits inside the ASIC 2 to each other. The internal bus 4 is connected to a plurality of devices such as a PCI bus, but may be a serial bus (PCI-Express) instead of a parallel bus. The CPU 5 is a central processing unit that executes control by a program. The bus monitoring unit 6 is means for detecting the idle time of the internal bus. The plotter 7 is a device that prints an image on paper. The main memory 8 is a DDR-SDRAM. The rest area 9 is an area where power is not supplied in the rest mode and the energy saving mode. The memory control unit 10 is means for controlling the main memory 8.

  The controller board 1 includes an ASIC 2, a main memory 8, an operation unit, an HDD, a board power control unit, an external power control unit, and the like. The ASIC 2 includes a bus monitoring unit 6, a memory control unit 10, an operation unit I / F, an HDD I / F, a general-purpose I / OI / F, a memory card I / F, an energy saving management unit 3, A packet filter unit (PF) for selecting packets, a network packet engine processing unit (PE) for processing packets, and a PCI I / F are installed. Inside the ASIC 2, there is an area where the power supply can be controlled, that is, the rest area 9, and an area where power is always supplied other than the rest area 9. The rest area 9 is an AISC PCI I / F, a memory card I / F, an operation unit I / F, an HDD I / F, and a general-purpose I / O I / F. The rest area 9 is an area not directly related to the network operation. A plotter 7 is connected to the internal bus 4 via a PCI I / F.

  The function and operation of the printer according to the first embodiment of the present invention configured as described above will be described. First, an outline of the power supply control function of the printer will be described. The bus monitoring unit 6 detects that the idle time of the internal bus 4 has exceeded the threshold value, and outputs a bus empty signal. Bus idle time detection can be realized by a method of monitoring a command strobe signal or a method of monitoring a read / write signal.

  The energy saving management unit 3 switches the power supply state to the sleep mode according to the bus empty signal. The sleep mode is an operation mode in which the power supply of all the circuits including the CPU 5 and the main memory 8 is set to the minimum except for the minimum necessary circuit including a part of the data input / output unit. The energy saving management unit 3 instructs the memory control unit 10 to output a self-refresh command to the main memory 8 and stops the power supply to the CPU 5. Alternatively, power supply can be set to a minimum by stopping the supply of the clock to the CPU 5. The memory control unit 10 switches the main memory 8 from the normal operation mode to the self refresh mode.

  When receiving the print data, the data input unit notifies the energy saving management unit 3 of a request to return to the normal operation mode. The energy saving management unit 3 switches the CPU 5, the main memory 8, and the data input unit to the normal operation mode in response to the return request. When the data input unit receives data to be processed by the CPU 5 in the sleep mode state, the data input unit notifies the energy saving management unit 3 of a request for switching to the energy saving mode in which the CPU 5 and the main memory 8 operate. The energy saving management unit 3 switches the CPU 5 and the main memory 8 to the normal operation mode according to the transition request.

  Next, the function of each part will be described with reference to FIG. All control and data transfer are performed via the internal bus 4. The energy saving management unit 3 of the ASIC 2 controls the power of the CPU 5, the power of the rest area 9 inside the ASIC 2, the board power control unit, and the external power control unit. Further, the power consumption of the main memory 8 is controlled via the memory control unit 10. When the energy saving management unit 3 instructs the memory control unit 10 to enter the low power consumption mode, the main memory 8 enters the self-refresh mode and enters the low power consumption mode in which the storage state of the main memory 8 is saved. When the energy saving management unit 3 instructs to shift to the normal mode or the energy saving mode, the main memory 8 enters the normal mode and can be accessed via the internal bus 4. When returning to the normal mode, the main memory 8 naturally returns to the state before the energy saving state.

  Next, each mode and state transition will be described with reference to FIG. Although not shown in FIG. 2, when the printer is turned on, power is supplied to the ASIC 2 and the energy saving management unit 3 puts the printer into the normal mode. In the normal mode, the energy saving management unit 3 puts the CPU 5 and the main memory 8 into a normal operation state. Furthermore, power supply to the sleep area 9 is started, and power is supplied to each unit from the board power control unit and the external power control unit. In the normal mode, when all the applications running on the CPU 5 are in an idle state, the bus monitoring unit 6 is activated by the energy saving management unit 3. In the bus monitoring unit 6, a circuit (CPU, PE, IPU, external I / F, operation unit I / F, HDD I / F circuit, etc.) connected to the internal bus 4 has finished using the internal bus 4. After that, the bus time is measured. When the bus idle time exceeds a predetermined time, the mode shifts to the sleep mode.

  In the sleep mode, the energy saving management unit 3 stops the power supply to the CPU 5 or stops the clock supply, and sets the main memory 8 to the low power consumption mode. Further, the power supply to the rest area 9 inside the ASIC 2 is stopped, the power supply from the board power control unit to the memory card, the operation unit, and the HDD is stopped, and the power supply to the plotter 7 is stopped by the external power supply control unit. . If the packet filter unit (PF) determines that a non-print request packet has been received for a packet received from the network during the sleep mode, the packet filter unit (PF) switches to the energy saving management unit 3 and switches to the energy saving mode. Instruct them to do so. When the network packet filter (PF) detects a print request packet in the pause mode, the energy saving management unit 3 controls to shift to the normal mode.

  In the energy saving mode, the energy saving management unit 3 sets the CPU 5 and the main memory 8 to the normal operation mode. Further, the power supply to the sleep area 9 inside the ASIC 2 is stopped, the power supply from the board power control unit to the memory card, the operation unit, and the HDD is stopped, and the power supply from the external power supply control unit to the plotter 7 is stopped. . When the bus idle time exceeds a predetermined time in the energy saving mode, the mode shifts to the sleep mode. Even if the designated time has elapsed, the packet filter unit (PF) shifts to the sleep mode even if the received data addressed to the own station is not detected. When the network packet filter (PF) detects a print request packet in the energy saving mode, the energy saving management unit 3 controls to shift to the normal mode.

  As described above, in the first embodiment of the present invention, when the idle time of the internal bus to which the CPU, the main memory, and the data input / output unit are connected exceeds the threshold, the printer is removed from the minimum necessary circuit. Switch to the sleep mode that sets the power supply of all circuits to the minimum, switch to the normal operation mode when print data is received, and if the CPU 5 receives data to be processed during the sleep mode, the CPU The power consumption of the printer can be greatly reduced because it is configured to switch to the energy saving mode in which the main memory operates.

  In the second embodiment of the present invention, when the idle time of the plotter and the scanner exceeds a certain time, the power supply to the plotter and the scanner is stopped and the print standby mode is switched, and the CPU, the main memory, and the data input / output unit are connected. When the idle time of the internal bus exceeds the threshold, it switches to the sleep mode that sets the power supply to all circuits except the minimum necessary circuit to the minimum, and switches to the normal operation mode when print data is received. When the printer receives data that does not require print processing but needs to be processed by the CPU, it stops the power supply to the plotter and scanner and switches the CPU and main memory to the normal operation mode.

  FIG. 2 is a functional block diagram of the multifunction peripheral according to the second embodiment of the present invention and a state transition diagram regarding the power consumption mode of the multifunction peripheral. In FIG. 2, a controller board 1 is a circuit portion that controls the multifunction peripheral. The controller board 1 is equipped with an ASIC 2, a main memory (DDR-SDRAM) 8, an operation unit, an HDD, a timer 11, and the like. The ASIC 2 is a central part of control including the CPU 5. The ASIC 2 includes a memory control unit 10 that controls the main memory 8, an operation unit I / F, an HDD I / F, an energy saving management unit 3, an IPU unit that performs image processing, and a packet that receives data. A packet filter unit (PF) for sorting, a network packet engine processing unit (PE) for processing packets from the packet filter unit (PF), an external I / F, a bus monitoring unit 6 and the like are mounted.

  The energy saving management unit 3 is means for managing the power supply of the multifunction machine. The internal bus 4 is a common signal bus that connects circuits inside the ASIC 2 to each other. The internal bus 4 is connected to a plurality of devices such as a PCI bus, but may be a serial bus (PCI-Express) instead of a parallel bus. The CPU 5 is a central processing unit that executes control by a program. The timer 11 is means for detecting the free time of the plotter and the scanner. The plotter 7 is a device that prints an image on paper. The plotter 7 is connected to the internal bus 4 through the external I / F together with the scanner. The main memory 8 is a DDR-SDRAM. The memory control unit 10 is means for controlling the main memory 8. The bus monitoring unit 6 is means for detecting the idle time of the internal bus.

  Inside the ASIC 2, there is an area where the power supply can be controlled, that is, the first hibernation area A, and an area where power is always supplied other than the first hibernation area A. The first sleep area A is an AISC operation unit I / F, HDD I / F, NVRAM I / F, ROM1 I / F, I2C / IF, external I / F, and IPU. . The first sleep area A is an area not directly related to the network operation. Even on the controller board 1, there is an area that can control the supply of electric power, which is a pause area B. The area of the controller board 1 other than the second sleep area B is an area related to network operation, and power is always supplied. In the third rest area C, there are the plotter 7 and the scanner. Each sleep region is not supplied with power in the sleep mode and the energy saving mode. The third pause area is not supplied with power even in the print standby mode.

  The function and operation of the multifunction machine according to the second embodiment of the present invention configured as described above will be described. First, an overview of the functions of the multifunction machine will be described with reference to FIG. All control and data transfer are performed via the internal bus 4. The energy saving management unit 3 of the ASIC 2 controls the power of the CPU 5, the power of the first sleep area A inside the ASIC 2, and the power of the second sleep area B of the controller board 1, and the main memory 8 via the memory control unit 10. Control the power consumption. Further, the power consumption of the plotter 7 and the scanner in the third rest area C is also controlled.

  When the standby instruction is received from the energy saving management unit 3 to the memory control unit 10, the main memory 8 is in a low power consumption self-refresh mode and only holds data. When the energy saving management unit 3 is notified of the transition to the normal mode or the energy saving mode, the main memory 8 enters the normal operation mode and can be accessed via the internal bus 4. When returning to the normal operation mode, the main memory 8 naturally returns to the state before the energy saving state.

  Next, each mode and state transition will be described with reference to FIG. In the normal mode, the energy saving management unit 3 puts the CPU 5 and the main memory 8 into a normal operation state. Furthermore, electric power is supplied to each rest area. In the normal mode, the CPU 5 and the timer 11 monitor the idle time when the plotter 7 and the scanner are not used. When the plotter 7 and the scanner are not used for a predetermined time, the CPU 5 instructs the energy saving management unit 3 to shift from the normal mode to the print standby mode. When instructed to shift to the print standby mode, the energy saving management unit 3 stops the power supply to the plotter 7 and the scanner in the third pause region C.

  In the print standby mode, power supply to the plotter 7 and the scanner is stopped, and printing and image reading are not performed. Other circuits remain in a normal operating state. When print data (print packet) is received via the data input / output unit (network PHY) in the print standby mode, the mode shifts to the normal mode. When the CPU 5 recognizes that there is a print packet, the CPU 5 notifies the energy saving management unit 3 of the transition to the normal mode and restarts the power supply to the plotter 7 and the scanner in the third pause region C. When power supply to the plotter 7 is resumed, image data is transferred to the plotter 7 via the external I / F and printing is performed. In the print standby mode, the bus monitoring unit 6 has a circuit (CPU, PE, IPU, external I / F, operation unit I / F, HDD I / F circuit, etc.) connected to the internal bus 4 The time after using 4 is measured as the bus idle time. When the bus empty time exceeds a predetermined time, the energy saving management unit 3 is notified and shifts to the sleep mode.

  In the sleep mode, the power supply to the CPU 5 is stopped or the clock supply is stopped, and the main memory 8 is put into a standby state. Further, the power supply to the first pause region A inside the ASIC 2 is stopped. Further, the power supply to the second pause area B and the third pause area C (plotter 7 and scanner) of the controller board 1 is stopped. When the print request packet is received in the pause mode, the packet filter unit notifies the energy saving management unit 3. The energy saving management unit 3 shifts to the print standby mode. If the packet filter unit (PF) determines that a non-print request packet has been received for a packet received from the network during the sleep mode, the packet filter unit (PF) switches to the energy saving management unit 3 and switches to the energy saving mode. Notify you.

  In the energy saving mode, the energy saving management unit 3 puts the CPU 5 and the main memory 8 into a normal operation state. The power supply to the first pause area A inside the ASIC 2, the second pause area B and the third pause area C (plotter 7 and scanner) of the controller board 1 is stopped. To put the main memory 8 in the normal operation state is to release the self-refresh mode in the memory control unit 10. In the energy saving mode, when the bus idle time exceeds a predetermined time, the mode shifts to the suspension mode. When the print request packet is received in the energy saving mode, the packet filter unit notifies the energy saving management unit 3 and the energy saving management unit 3 shifts to the print standby mode.

  As described above, according to the second embodiment of the present invention, when the idle time of the plotter and the scanner exceeds a certain time, the power supply to the plotter and the scanner is stopped and the print standby mode is switched. When the idle time of the internal bus to which the memory and data input / output unit are connected exceeds the threshold, the printer switches to the sleep mode in which the power supply of all circuits except the minimum necessary circuits is set to the minimum. Switch to the normal operation mode.When data that does not require printing processing but is required to be processed by the CPU is received, the CPU and main memory are set to the normal operation mode with the power supply to the plotter and scanner stopped. Since the configuration is switched, the power consumption of the multifunction device can be greatly reduced.

  The image forming apparatus of the present invention is optimal as an image forming apparatus that can greatly reduce power consumption during standby. It is also suitable as a network scanner, network printer, or network-connected multifunction device.

FIG. 2 is a functional block diagram of the printer according to the first embodiment of the present invention and a state transition diagram regarding the power consumption mode of the printer. FIG. 6 is a functional block diagram of a multifunction peripheral according to a second embodiment of the present invention and a state transition diagram regarding a power consumption mode of the multifunction peripheral.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Controller board, 2 ... ASIC, 3 ... Energy-saving management part, 4 ... Internal bus, 5 ... CPU, 6 ... Bus monitoring part, 7 ... Plotter, 8 ..Main memory, 9 ... rest area, 10 ... memory control unit, 11 ... timer.

Claims (10)

  An internal bus to which the CPU, main memory and data input / output unit are connected; bus monitoring means for detecting that the idle time of the internal bus has exceeded a threshold and outputting a bus empty signal; and An energy saving management unit that switches to a sleep mode that minimizes the power supply of all circuits including the CPU and the main memory, except for a minimum necessary circuit including a part of the data input / output unit, according to a signal; An electronic apparatus comprising:   The energy saving management unit includes means for instructing a memory control unit to output a self-refresh command to the main memory, and means for stopping supply of power or clock to the CPU. Item 1. An electronic device according to Item 1.   The data input unit includes means for notifying the energy saving management unit of a request to return to a normal operation mode when receiving data to be output processed, the energy saving management unit responding to the return request to the CPU 2. The electronic apparatus according to claim 1, further comprising means for switching the main memory and the data input unit to a normal operation mode.   The data input unit is configured to notify the energy saving management unit of a transition request to an energy saving mode in which the CPU and the main memory operate when data to be processed by the CPU is received in the sleep mode state. The electronic device according to claim 1, further comprising a unit that switches the CPU and the main memory to a normal operation mode in response to the transition request.   An internal bus to which a CPU, a main memory and a data input / output unit are connected; an image printing unit for processing data received by the data input / output unit by the CPU to output an image; and an idle state of the internal bus Bus monitoring means for detecting that the time has exceeded a threshold and outputting a bus empty signal, and the CPU excluding a necessary minimum circuit including a part of the data input / output unit according to the bus empty signal And an energy saving management unit that switches to a sleep mode that minimizes power supply to all circuits including the main memory.   The energy saving management unit includes means for instructing a memory control unit to output a self-refresh command to the main memory, and means for stopping supply of power or clock to the CPU. Item 6. The image forming apparatus according to Item 5.   The data input unit includes means for notifying the energy saving management unit of a request to return to a normal operation mode when data to be processed by the image printing unit is received, and the energy saving management unit responds to the return request. 6. The image forming apparatus according to claim 5, further comprising means for switching all circuits to a normal operation mode.   The data input unit includes means for notifying the energy saving management unit of a CPU return request when data that does not require processing by the image printing unit but requires processing by the CPU is received. 6. The image forming apparatus according to claim 5, further comprising means for switching the CPU and the main memory to a normal operation mode while power supply to the image printing unit is stopped in response to the CPU return request.   When it is detected that the idle time of the internal bus to which the CPU, the main memory, and the data input / output unit are connected exceeds the threshold, the supply of power or clock to the CPU is stopped, and the memory is stored in the main memory. A control self-refresh command is issued to switch to a sleep mode in which the power supply of all circuits including the CPU and the main memory is set to a minimum except for a minimum necessary circuit including a part of the data input / output unit. When the data to be output is received by the data input unit, the mode is switched to a normal operation mode, and when the data to be processed by the CPU is received by the data input unit during the sleep mode, the CPU and A power supply control method characterized by switching to an energy saving mode in which the main memory operates.   When it is detected that the idle time of the image printing unit has exceeded a certain time, the power supply to the image printing unit is stopped and the idle time of the internal bus to which the CPU, main memory, and data input / output unit are connected Is detected, the supply of power or clock to the CPU is stopped, a memory control self-refresh command is issued to the main memory, and the minimum necessary including part of the data input / output unit is included. When all the circuits including the CPU and the main memory are switched to a sleep mode in which the power supply of all the circuits is set to a minimum, and data to be processed by the image printing unit is received, all the circuits are normally set. When the CPU receives the data that does not require processing by the image printing unit but requires processing by the CPU, the power supply to the image printing unit is stopped and the previous processing is stopped. Power supply control method characterized by switching the main memory in normal operating mode.

Images