Abstract:
The present invention provides a global positioning system (GPS) and a method for implementing the system. The GPS includes a control unit, a GPS RF processing circuit and a storage unit. The control unit includes a microprocessor and a mask ROM storing reference information. The GPS RF processing circuit is coupled to the control unit for receiving an RF signal, transforming the RF signal into a base-band or an intermediate frequency signal and transmitting the base-band or the intermediate frequency signal to the control unit. The storage unit is coupled to the control unit to temporally store a program code. The microprocessor executes the program code and refers to the reference information to achieve global positioning.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Taiwan application Serial No. 95127064, filed Jul. 25, 2006, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a global positioning system (GPS) and a method for implementing the same and, more particularly, to a GPS with a mask read-only memory (ROM) and a method for implementing the GPS. The present invention also relates to a control integrated circuit (IC) of the GPS with the mask ROM and a method for manufacturing the control IC. 
     2. Description of the Prior Art 
     The GPS has been widely used in various applications such as the car navigation system. Please refer to  FIG. 1 , which is a block diagram of a conventional GPS. The GPS  100  comprises a microprocessor  110 , a GPS radio-frequency (RF) processing circuit  120 , an audio signal processing unit  130 , a flash memory  140 , a synchronous dynamic random access memory (SDRAM)  150 , an I/O interface  160  and a display module  170 . The GPS RF processing circuit  120  receives an RF signal from a satellite via an antenna  125 , transforms the RF signal into a base-band signal and then transmits the base-band signal to the microprocessor  110 . Typically, the flash memory  140  is a NAND-type flash memory for storing a program code and map data. Before the program code is executed, the program code is stored in the SDRAM  150  that has a higher accessing speed. The microprocessor  110  executes the program code temporally stored in the SDRAM  150 , processes the base-band signal from the GPS RF processing circuit  120  and refers to the map data stored in the flash memory  140  so as to achieve positioning. The positioning information generated by the microprocessor  110  is broadcasted by a speaker  135  after being decoded and amplified by the audio signal processing unit  130  or displayed on the display module  170 . Moreover, the positioning information can also be transmitted to other electronic appliances such as a computer by way of the I/O interface  160  coupled to the microprocessor  110 . Typical I/O interface specifications include the universal serial bus (USB), and the universal asynchronous receiver transmitter (UART). 
     Generally, the map data occupies a large memory space and thus the GPS  100  requires a large-capacity flash memory  140 , which leads to an increase in cost. 
     SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to provide a global positioning system (GPS) with a mask read-only memory (ROM) and a method for implementing the GPS wherein the massive map data is stored in the mask ROM so as to reduce the cost. 
     In order to achieve the foregoing object, the present invention provides a GPS, including a control unit, a GPS radio-frequency (RF) processing circuit and a storage unit. The control unit includes a microprocessor and a mask ROM which stores reference information. The GPS RF processing circuit is coupled to the control unit for receiving an RF signal, transforming the RF signal into a base-band or an intermediate frequency signal and transmitting the base-band or the intermediate frequency signal to the control unit. The storage unit is coupled to the control unit to temporally store a program code. The microprocessor executes the program code and refers to the reference information to achieve global positioning. 
     The present invention further provides a control integrated circuit (IC) of a GPS. The control IC includes a microprocessor and a mask ROM which stores reference information. The microprocessor operates and refers to the reference information to achieve global positioning. 
     The present invention further provides a method for manufacturing a control IC of a GPS. The method includes steps of: manufacturing a microprocessor and a mask ROM of the control IC on a semiconductor substrate; and designing at least a data mask for defining the data content in the mask ROM. The microprocessor operates and accesses the data content in the mask ROM to achieve global positioning. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects, spirits and advantages of the preferred embodiment of the present invention will be readily understood by the accompanying drawings and detailed descriptions, wherein: 
         FIG. 1  is a block diagram of a conventional GPS; 
         FIG. 2  is a block diagram of a GPS according to a first embodiment of the present invention; 
         FIG. 3  is a block diagram of a GPS according to a second embodiment of the present invention; 
         FIG. 4  is a block diagram of a GPS according to a third embodiment of the present invention; and 
         FIG. 5  is a block diagram of a GPS according to a fourth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. Also, the term “couple” is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is coupled to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. 
     Please refer to  FIG. 2 , which is a block diagram of a GPS according to a first embodiment of the present invention. The GPS  200  comprises a control unit  210 , a GPS radio-frequency (RF) processing circuit  220 , an audio signal processing unit  230 , a synchronous dynamic random access memory (SDRAM)  250 , an I/O interface  260  and a display module  270 . The GPS RF processing circuit  220  receives an RF signal from a satellite via an antenna  225 , transforms the RF signal into a base-band or an intermediate frequency signal and then transmits the base-band or the intermediate frequency signal to the control unit  210 . In the present embodiment, the control unit (or referred to as a control IC)  210  integrates a microprocessor  212  and a mask ROM  215 . The microprocessor  210  is made on a semiconductor substrate through a standard semiconductor manufacturing process. With at least a data mask, the mask ROM  215  is manufactured on the same semiconductor substrate. In other words, the microprocessor  212  and the mask ROM  215  are simultaneously manufactured on one semiconductor chip. The data stored in the mask ROM  215  can be changed by changing the pattern of the data mask. Therefore, when it comes to changing the data stored in the mask ROM  215 , it is only required to modify or re-design the data mask. In the present embodiment, the mask ROM  215  stores a map data and a program code that are conventionally stored in the flash memory  140  of a conventional GPS  100 . That is, the data mask is designed based on the map data and the program code, and thus the mask ROM  215  which is manufactured according to the data mask stores the map data and the program code. When the GPS operates, the microprocessor  212  reads the program code from the mask ROM  215  and temporally stores the program code in the SDRAM  250  before the program code is executed. The microprocessor  212  processes the base-band or the intermediate frequency signal from the GPS RF processing circuit  220  and refers to the map data stored in the mask ROM  215  so as to achieve positioning. The positioning information is broadcasted by a speaker  235  after being decoded and amplified by the audio signal processing unit  230  or displayed on the display module  270 . Moreover, the positioning information can also be transmitted to other electronic appliances such as a computer, a PDA and so on by way of the I/O interface  260  coupled to the control unit  210 . Typical I/O interface specifications include the universal serial bus (USB), the universal asynchronous receiver transmitter (UART), Bluetooth and etc. 
     In the present embodiment, the program code and the massive map data are both stored in the mask ROM  215  rather than a flash memory. Compared to a flash memory, the mask ROM  215  is advantageous due to its low manufacturing cost. In addition, only one or more than one data mask has to be changed when the content stored in the mask ROM  215  is required to be updated. Therefore, the cost for the GPS with the mask ROM is significantly reduced. 
     Please refer to  FIG. 3 , which is a block diagram of a GPS according to a second embodiment of the present invention. The GPS  300  comprises a control unit  310 , a GPS radio-frequency (RF) processing circuit  220 , an audio signal processing unit  230 , a synchronous dynamic random access memory (SDRAM)  250 , an I/O interface  260 , a display module  270  and a flash memory  320 . It is noted that elements shown in the present embodiment possess the same function as those designated by the same number in the previous embodiment, and therefore the description thereof is omitted. Similarly, the control unit (or referred to as a control IC)  310  integrates a microprocessor  312  and a mask ROM  315 . The method for manufacturing the control unit  310  is similar to the method for manufacturing the control unit  210  and the description thereof is omitted. What is different is that, in the present embodiment, the mask ROM  315  is used for storing the map data, while the program code is stored in the flash memory  320 . In other words, the data mask for manufacturing the mask ROM  315  is designed according to the map data and, thus, the mask ROM  315  manufactured according to the data mask stores the map data. When the GPS operates, the microprocessor  312  temporally stores the program code in the SDRAM  250  before the program code is executed. The microprocessor  312  processes the base-band or the intermediate frequency signal from the GPS RF processing circuit  220  and refers to the map data stored in the mask ROM  315  so as to achieve positioning. In one preferred embodiment, the flash memory  320  is a NOR-type flash memory. Since the NOR-type flash memory has advantages such as a high speed, it is proper to use the NOR-type flash memory for storing the program code and the update process of the program code would be simplified in the GPS  300 . Compared to map data, the program code requires a relatively small memory capacity and, thus, the flash memory does not require a large memory capacity. In this case, the massive map data is still stored in the mask ROM  315 . Compared to the conventional GPS  100 , the GPS  300  in the present embodiment is advantageous due to its lower cost. Similarly, in the present embodiment, only one or more than one data mask has to be changed when the map data is required to be updated. As for updating the program code, only the content in the flash memory  320  has to be updated. Since the speed for accessing the program code is accelerated, the overall performance of the GPS is enhanced. 
     Please refer to  FIG. 4 , which is a block diagram of a GPS according to a third embodiment of the present invention. The GPS  400  comprises a control unit  410 , a GPS radio-frequency (RF) processing circuit  220 , an audio signal processing unit  230 , a synchronous dynamic random access memory (SDRAM)  250 , an I/O interface  260 , a display module  270  and a flash memory  420 . It is noted that elements shown in the present embodiment possess the same function as those designated by the same number in the previous embodiment, and therefore the description thereof is omitted. Similarly, the control unit (or referred to as a control IC)  410  integrates a microprocessor  412  and a mask ROM  415 . The method for manufacturing the control unit  410  is similar to the method for manufacturing the control unit  210  and the description thereof is omitted. Similarly, in the present embodiment, the mask ROM  415  is used for storing the map data and the program code. In other words, the data mask for manufacturing the mask ROM  415  is designed according to the map data and the program code and, thus, the mask ROM  415  manufactured according to the data mask stores the map data and the program code. When the GPS operates, the microprocessor  412  temporally stores the program code in the SDRAM  250  before the program code is executed. The flash memory  420  stores modified information of the map data. Before the microprocessor  412  accesses the map data, it searches for the modified information of the map data stored in the flash memory  420 . The microprocessor  412  accesses unmodified map data from the mask ROM  415  if no required modified information is found. In one preferred embodiment, the flash memory  420  is a NAND-type flash memory. Similarly, in the present embodiment, only one or more than one data mask has to be changed when the map data is required to be updated. The GPS  400  is advantageous in that the modified information of the map data can be stored in an additional flash memory  420  if the modified information does not require a large memory capacity. Therefore, there is no need to update the mask when the map data is only partially updated. Please note the flash memory  420  can be built in the GPS  400  or externally connected to the GPS  400 , which provides more flexibility in partially updating the map data. 
     Please further refer to  FIG. 5 , which is a block diagram of a GPS according to a fourth embodiment of the present invention. The GPS  500  comprises a control unit  510 , a GPS radio-frequency (RF) processing circuit  220 , an audio signal processing unit  230 , a synchronous dynamic random access memory (SDRAM)  250 , an I/O interface  260 , a display module  270 , a flash memory  320  and a flash memory  420 . The present embodiment is a combination of the previous two embodiments. It is noted that elements shown in the present embodiment possess the same function as those designated by the same number in the previous embodiment, and therefore the description thereof is omitted. Similarly, the control unit (or referred to as a control IC)  510  integrates a microprocessor  512  and a mask ROM  515 . The method for manufacturing the control unit  510  is similar to the method for manufacturing the control unit  210  and the description thereof is omitted. In the present embodiment, the mask ROM  515  is used for storing the map data, while the program code is stored in the flash memory  320 . In other words, the data mask for manufacturing the mask ROM  515  is designed according to the map data and, thus, the mask ROM  515  manufactured according to the data mask stores the map data. When the GPS operates, the microprocessor  512  temporally stores the program code in the SDRAM  250  before the program code is executed. The flash memory  420  stores modified information of the map data. Before the microprocessor  512  accesses the map data, it searches for the modified information of the map data stored in the flash memory  420 . The microprocessor  512  accesses unmodified map data from the mask ROM  515  if no required modified information is found. In one preferred embodiment, the flash memory  320  is a NOR-type flash memory and the flash memory  420  is a NAND-type flash memory. Similarly, in the present embodiment, the flash memory  420  can be built in the GPS  500  or externally connected to the GPS  500 . Please note that the programs code and the modified information of the map data can be stored in the same flash memory, for example, the flash memory  320  or the flash memory  420 . In this case, the GPS  500  requires only one flash memory. 
     In the present invention, a mask ROM is integrated on a control chip of the GPS such that the massive map data can be stored in a relatively low-cost mask ROM and the program code can be stored in the same mask ROM or other storage unit. It is easy to change the content in the mask ROM by modifying or re-designing the pattern of the mask when the map data has to be updated. If the map data is only partially updated, the modified information of the map data can be stored in a build-in flash memory or an externally connected flash memory, which provides more flexibility in partially updating the map data. 
     Although this invention has been disclosed and illustrated with reference to particular embodiments, the principles involved are susceptible for use in numerous other embodiments that will be apparent to persons skilled in the art. This invention is, therefore, to be limited only as indicated by the scope of the appended claims.