Patent Publication Number: US-2003231171-A1

Title: Electronic apparatus and suspend/resume method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-175611, filed Jun. 17, 2002, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] The present invention relates to an electronic apparatus with a display device such as an LCD, and a suspend/resume method for the apparatus. In particular, the present invention relates to an electronic apparatus and a method of suspending/resuming the apparatus, which can further reduce power consumption at the time of suspend, without causing a long-time resume.  
       [0004] 2. Description of the Related Art  
       [0005] Recently, portable electronic apparatuses, such as personal digital assistant (PDA), which can be driven by battery, have come into wide use. In these apparatuses, various power-saving mechanisms are provided, to lengthen the life of the battery, even if only slightly.  
       [0006] Further, electronic apparatuses of this kind generally have a suspend/resume function which stores the state of the computer at the time of turning off the power of the computer and restores the stored state, such that the last work can be instantly resumed when the computer is turned on again.  
       [0007] In the meantime, if an electronic apparatus is suspended by the suspend/resume function, in the conventional art, power supply to a system memory and a video memory is continued, to maintain their contents. However, in recent apparatuses, a video memory is included in a display controller, and thus it is required to continue power supply to the whole display controller to use the suspend/resume function. Thus, this method is not very preferable from the viewpoint of reducing power consumption.  
       [0008] In consideration of the above, a suspend/resume method disclosed in Jpn. Pat. Appln. KOKAI Pub. No. 11-259162 transmits the contents of a video memory to a hard disk drive, and then transfers the apparatus into a suspended state. According to this method, power supply to a video memory, that is, power supply to a display controller can be cut off during suspend, and unnecessary power consumption can be prevented.  
       [0009] However, since this method restores the contents of the video memory at the time of resume, using the hard disk drive, the resume processing requires much time.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010] An embodiments of the present invention is to provide an electronic apparatus and a suspend/resume method for the apparatus, which can further reduce power consumption at the time of suspending, without causing a long-time resuming.  
       [0011] According to an aspect of the invention, it provides an electronic apparatus capable of executing a suspend processing, comprising: a first memory which stores system data; a second memory which stores display data; a suspend instruction unit configured to determine whether or not to execute the suspend processing; a suspend unit configured to save the display data stored in the second memory to the first memory, when the suspend instruction unit has determined to execute the suspend processing; and a power control unit configured to stop power supply to the second memory, and maintain power supply to the first memory.  
       [0012] Accordingly, contents of a video memory are saved in a predetermined area in a system memory, thus power supply to a video memory or a display controller including the video memory can be cut off. Further, at the time of resume, the contents of the video memory can be restored with a very short time by using a system memory, unlike in the case of using a hard disk drive.  
       [0013] Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The features and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
     [0014] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
     [0015]FIG. 1 is a diagram showing an appearance of an electronic apparatus according to an embodiment of the present invention.  
     [0016]FIG. 2 is a block diagram showing a part of a main structure of the electronic apparatus of the embodiment.  
     [0017]FIG. 3 is a flow chart showing a suspend processing of the electronic apparatus of the embodiment.  
     [0018]FIG. 4 is a flow chart showing a resume processing of the electronic apparatus of the embodiment.  
     [0019]FIG. 5 is a diagram showing a personal computer to which a method of the present invention is applicable. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0020] An embodiment of the present invention will now be described with reference to the drawings.  
     [0021]FIG. 1 is a diagram showing an appearance of an electronic apparatus according to an embodiment of the present invention.  
     [0022] The electronic apparatus is a personal digital assistant (PDA) having a proper size such that a user can hold it by one hand. The PDA  10  is configured to be driven by a battery, and has a suspend/resume function by which the last work on the PDA can be instantly resumed when the PDA  10  is turned on again. A liquid crystal display (LCD)  16  for data display is provided on a front surface of the PDA.  
     [0023]FIG. 2 is a block diagram showing a part of a main structure of the electronic apparatus of the embodiment.  
     [0024] As shown in FIG. 2, in the PDA  10 , a bus A for transmitting and receiving data is laid. Further, with the bus A serving as a backbone, CPU  11 , a bus/memory controller  12 , a basic input/output system (BIOS)  13 , a system memory  14 , a display controller  15 , the LCD  16 , and power supply controller (PSC)  17  are provided.  
     [0025] The CPU  11  controls the whole PDA  10 , and operates in accordance with description of a program stored in the system memory  14 . The bus/memory controller  12  has a bridge function of bridging a CPU local bus and the bus A, and a function of a cashe for the system memory  14 .  
     [0026] The BIOS  13  drives and controls various peripheral devices, such as a hard disk unit (not shown), of the PDA  10 . The BIOS  13  realizes the above suspend/resume function.  
     [0027] The system memory  14  is a memory device serving as a main storage of the PDA  10 , and stores a program describing an operation sequence of the CPU  11 , and data inputted and outputted from the program. Although the system memory  14  is a volatile memory, power supply to the system memory  14  is continued even during suspend.  
     [0028] Further, in the PDA  10  of the embodiment, a VRAM save area  141  which only the BIOS  13  recognizes is reserved on the system memory  14 . The area is reserved by notifying an operating system of a smaller size than the actual size of the system memory  14  (a size obtained by deducting the size of the VRAM save area  141  from the actual size of the system memory  14 ), when, for example, the operating system has started.  
     [0029] The display controller  15  includes a VRAM  151  for storing display data generated by the CPU  11 , and performs control to display the display data stored in the VRAM  151  on the LCD  16 .  
     [0030] The PSC  17  is supply power to device provided in the PDA  10 . When the suspend has done, the PSC  17  supplies the power to the system memory  14 , and stop supplying the power to the display controller.  
     [0031] Next, with reference to FIGS. 3 and 4, the operation sequence of the PDA  10 , having the above structure, at the time of suspend/resume will now be described.  
     [0032]FIG. 3 is a flow chart showing a suspend processing of the electronic apparatus of the embodiment.  
     [0033] At the time of suspend, the BIOS  13  detects the suspend instruction. Then the BIOS  13  reads the display data stored in the VRAM  151  (step A 1 ), and saves the read display data in the VRAM save area  141  of the system memory  14  (step A 2 ). Then, the BIOS  13  checks whether all the contents of the VRAM  151  have been saved (step A 3 ) and, if not (NO of step A 3 ), repeats the processing from step A 1 . If they have been saved (YES of step A 3 ), the BIOS  13  turns off the power of the PDA.  
     [0034] Further, FIG. 4 is a flow chart showing a resume processing of the electronic apparatus of the embodiment.  
     [0035] At the time of resume, first the BIOS  13  reads the display data, which was saved at the time of suspend, from the VRAM save area  141  of the system memory  14  (step B 1 ), and restores the read display data in the VRAM  151  (step B 2 ). Then, the BIOS  13  checks whether all the contents of the VRAM  151  have been restored (step B 3 ) and, if not (NO of step B 3 ), repeats the processing from step B 1 . If they have been restored (YES of step B 3 ), the BIOS  13  starts the system.  
     [0036] As described above, the PDA  10  of the embodiment saves the contents of the VRAM  151  in the VRAM save area  141  on the system memory  14  at the time of suspend, and thus power supply to the display controller  15  including the VRAM  151  can be cut off, and the power consumption during suspend can be reduced.  
     [0037] Further, at the time of resume, the contents of the VRAM  151  are restored by using the system memory  14 , and thus the resume can be completed with a very short time.  
     [0038] Although in the above the present invention has been explained with the PDA  10  as an example, the method of the present invention is also applicable to, for example, a personal computer as shown in FIG. 5. Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.