Abstract:
A method for transmitting and receiving data between an MPU and a memory operating in mutually different operating voltages in PLC is proposed, the method including: outputting, by the MPU, a CS (Chip Select) signal and an address signal in order to read data by approaching to the memory; outputting, by an OR gate, an activation signal for activating a data input buffer by receiving the CS signal and the address signal; outputting, by an access signal output buffer, a memory access signal for operation of the memory by receiving the CS signal and the address signal; outputting, by the memory, data requested by the MPU to the data input buffer by responding to the memory access signal; and outputting, by the data input buffer, the received data to the MPU by receiving the data outputted by the memory.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2014-0137572, filed on Oct. 13, 2014, the contents of which are all hereby incorporated by reference herein in its entirety. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    1. Field 
         [0003]    The teachings in accordance with the exemplary embodiments of this present disclosure generally relate to a method for transmitting and receiving data between an MPU and a memory that operate in mutually different operating voltages in PLC. 
         [0004]    2. Background 
         [0005]    Concomitant with requirement of high speed operation for semiconductor devices such as MPUs (Micro Processing Units), memories and logic ICs, an operating frequency thereto is also required to increase whereby power consumption is also increased. The increased power consumption can result in heated ICs and energy wastes, which brings forth a trend of speedy transmission and receipt of data and realization of low operating voltages. 
         [0006]    Meantime, voltage levels of ICs used in PLCs (Programmable Logic Controllers) widely used for controlling automation facilities at industrial sites are 1.2V, 3.3V and 5V, which means that operating voltages are different, such that methods for transmitting and receiving data between devices have surfaced as new issues. 
         [0007]    In general, the PLC exchanges data with memories, communication controllers and expansion modules based on the MPU. Transmission and receipt of data among devices each having a different operating voltages have conventionally used a unidirectional communication method based on the MPU. 
         [0008]      FIG. 1  illustrates a data flow based on unidirectional communication among devices each having a different operating voltage in a PLC according to a prior art. 
         [0009]    Referring to  FIG. 1 , an operating voltage of an MPU ( 1 ) is 3.3V, and an operating voltage of an input sensor ( 2 ) and an output driver ( 3 ) is 5V, and an operating voltage of the input sensor ( 2 ) and the output driver ( 3 ) is different from that of the MPU ( 1 ). 
         [0010]    At this time, the MPU ( 1 ) may receive data outputted from the input sensor ( 2 ), and transmit the data to be outputted to the outside to the output driver ( 3 ). Meanwhile, the input sensor ( 2 ) may simply transmit data to the MPU ( 1 ), but receive no data from the MPU ( 1 ), and the output driver ( 3 ) may simply receive the data from the MPU ( 1 ), but transmit no data to the MPU ( 1 ). Thus, the MPU ( 1 ) may perform bidirectional communication that receives and transmits the data, while the input sensor ( 2 ) and the output driver ( 3 ) perform a unidirectional communication. 
         [0011]    Meanwhile, an input buffer ( 4 ) may be interposed between the input sensor ( 2 ) and the MPU ( 1 ), and an output buffer ( 5 ) may be interposed between the MPU ( 1 ) and the output driver ( 3 ), because operating voltages of the input sensor ( 2 ) and the output driver ( 3 ) are dissimilar to the operating voltage of MPU ( 1 ). 
         [0012]    At this time, the input buffer ( 4 ) may convert 5V data transmitted from the input sensor ( 2 ) to 3.3V data recognizable by the MPU ( 1 ) and transmit the converted 3.3 V data to the MPU ( 1 ), and the output buffer ( 5 ) may convert 3.3V data transmitted from the MPU ( 1 ) to 5V data recognizable by the output driver ( 3 ) and transmit the converted 5V data to the output driver ( 3 ). 
         [0013]    An OR gate ( 6 ) may be interposed between the MPU ( 1 ) and the input buffer ( 4 ) to output an enable signal (IN_CS) to the input buffer ( 4 ) by receiving a CS (Chip Select) signal and a RD (READ) signal outputted from the MPU ( 1 ). Furthermore, an OR gate ( 7 ) may be interposed between the MPU ( 1 ) and the output buffer ( 5 ) to output an enable signal (OUT_CS) to the output buffer ( 5 ) by receiving a CS (Chip Select) signal and a WR (WRITE) signal outputted from the MPU ( 1 ). 
         [0014]      FIG. 2  is a timing diagram illustrating that the MPU ( 1 ) receives data from the input sensor ( 2 ), and  FIG. 3  is a timing diagram illustrating that the MPU ( 1 ) transmits the data to the output driver ( 3 ). 
         [0015]    Because the input sensor ( 2 ) and the output driver ( 3 ) perform unidirectional communication, only time delay resultant from each configuration is generated as illustrated in  FIGS. 2 and 3 , where the MPU ( 1 ) may normally receive data from the input sensor ( 2 ) and may transmit the data to the output driver ( 3 ). 
         [0016]    As noted from the foregoing, the data transmission/reception between devices of different operating voltages were performed using the unidirectional communication method based on an MPU according to the prior art. Thus, a part performing the read/write such as a memory used a part having same operating voltage as that of the MPU. However, disadvantages have occurred where one memory is shared by MPUs having different operating voltages, as the MPUs are used for each function such as basic operation, communication and position control for performance enhancement. 
         [0017]    When one memory is used by the MPUs having different operating voltages as noted above, a problem occurs where an MPU having a different operating voltage from that of a memory cannot have a smooth transmission/reception of data with the memory, although an MPU having a same operating voltage as that of the memory can normally perform the transmission/reception of data with the memory. 
       SUMMARY 
       [0018]    The present disclosure has been made to solve the foregoing disadvantages/problems of the prior art and therefore an object of certain embodiments of the present disclosure is to provide a method for transmitting and receiving data between an MPU and a memory that operate in mutually different operating voltages in PLC. 
         [0019]    Technical problems to be solved by the present disclosure are not restricted to the above-mentioned description, and any other technical problems not mentioned so far will be clearly appreciated from the following description by the skilled in the art. 
         [0020]    The present disclosure is to solve at least one or more of the above problems and/or disadvantages in whole or in part and to provide at least advantages described hereinafter. In order to achieve at least the above objects, in whole or in part, and in accordance with the purposes of the present disclosure, as embodied and broadly described, and in one general aspect of the present invention, there is provided a method for transmitting and receiving data between an MPU and a memory operating in mutually different operating voltages in PLC, the method comprising: 
         [0021]    outputting, by the MPU, a CS (Chip Select) signal and an address signal in order to read data by approaching to the memory; 
         [0022]    outputting, by an OR gate, an activation signal for activating a data input buffer by receiving the CS signal and the address signal; 
         [0023]    outputting, by an access signal output buffer, a memory access signal for operation of the memory by receiving the CS signal and the address signal; 
         [0024]    outputting, by the memory, data requested by the MPU to the data input buffer by responding to the memory access signal; and 
         [0025]    outputting, by the data input buffer, the received data to the MPU by receiving the data outputted by the memory. 
         [0026]    Preferably, but not necessarily, the step of outputting the memory access signal may include outputting, by the access signal output buffer, the memory access signal by converting the CS signal and the address signal received from the MPU to a voltage level recognizable by the memory. 
         [0027]    Preferably, but not necessarily, the step of outputting the received data to the MPU may include outputting the data received by the data input buffer to the MPU by converting to a voltage level recognizable by the MPU. 
         [0028]    Preferably, but not necessarily, the address signal may be shifted at a time same as that of the CS signal. 
         [0029]    Preferably, but not necessarily, the CS signal and the address signal may maintain a level “LOW” to enable the OR gate to output the activation signal, while the step of outputting, by the memory, the data requested by the MPU to the data input buffer and the step of outputting the received data to the MPU are being performed. 
         [0030]    Preferably, but not necessarily, the address signal may be set as an uppermost bit of read area and write area that are made by respectively dividing a memory area to half. 
         [0031]    The method for transmitting and receiving data between an MPU and a memory in PLC according to the exemplary embodiments of the present disclosure has an advantageous effect in that data outputted from a memory can be read by an MPU without any loss by using an 1-bit address as an input of OR gate configured to output an activation signal for activating a data input buffer, whereby data transmission/reception can be made possible without data loss between the MPU and the memory that operate in mutually different operating voltages in PLC, and data transmission/reception can be made possible without data loss even if devices, each having a different operating voltage, are increased. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    The accompanying drawings included to provide a further understanding of the disclosure and incorporated in and constituted as a part of this application, illustrate embodiment(s) of the disclosure, and together with the description, serve to explain the principle of the disclosure. In the drawings: 
           [0033]      FIG. 1  illustrates a data flow based on unidirectional communication among devices each having a different operating voltage in a PLC according to a prior art; 
           [0034]      FIG. 2  is a timing diagram illustrating that an MPU receives data from an input sensor according to a prior art; 
           [0035]      FIG. 3  is a timing diagram illustrating that an MPU transmits data to an output driver according to a prior art; 
           [0036]      FIG. 4  is a data flowchart during memory read by using a level shifter; 
           [0037]      FIG. 5  is a timing diagram during memory read using a level shifter; 
           [0038]      FIG. 6  is a data flowchart during memory read by using an address signal according to the present disclosure; and 
           [0039]      FIG. 7  is a timing diagram during memory read by using an address signal according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0040]    Various exemplary embodiments will be described more fully hereinafter with reference to the accompanying drawings, in which some exemplary embodiments are shown. 
         [0041]    Advantages and features of the present disclosure may be understood more readily by reference to the following detailed description of exemplary embodiments and the accompanying drawings. Thus, the present disclosure is not limited to the exemplary embodiments which will be described below, but may be implemented in other forms. 
         [0042]    The particular embodiments disclosed herein are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. The present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope and principle of the general inventive concept to those skilled in the art. Furthermore, throughout the descriptions, the same reference numerals will be assigned to the same elements in the explanations of the figures, and explanations that duplicate one another will be omitted. 
         [0043]    Detailed descriptions of well-known functions, configurations or constructions are omitted for brevity and clarity so as not to obscure the description of the present disclosure with unnecessary detail. Accordingly, the meaning of specific terms or words used in the specification and claims should not be limited to the literal or commonly employed sense, but should be construed or may be different in accordance with the intention of a user or an operator and customary usages. Therefore, the definition of the specific terms or words should be based on the contents across the specification. 
         [0044]    The conventional technology is configured in a manner such that an input port and an output port are designed to control different devices, and therefore the conventional technology is not suitable for devices that must perform the read and write at the same time as a memory. 
         [0045]      FIG. 4  is a dataflow chart during memory read by using a level shifter and  FIG. 5  is a timing diagram during memory read using a level shifter. 
         [0046]    Referring to  FIGS. 4 and 5 , read (or reading) process between an MPU and a memory will be explained using a level shifter according to a prior art. Reference numeral  11  in  FIG. 4  is an MPU, which is connected to a memory ( 12 ) to transmit data to the memory ( 12 ), or to receive the data from the memory ( 12 ). 
         [0047]    Thus, although there was a unidirectional communication in  FIG. 1  where the MPU ( 1 ) receives data from the input sensor ( 2 ) and transmit the data to the output driver ( 3 ), an MPU ( 11 ) performs a bidirectional communication with the memory ( 12 ) in  FIG. 4 . Meanwhile, an input buffer ( 13 ), an output buffer ( 14 ) and two OR gates ( 15 ,  16 ) in  FIG. 4  have the same configuration as that of the input buffer ( 4 ), the output buffer ( 5 ) and the two OR gates ( 6 ,  7 ) in  FIG. 1 . 
         [0048]    In addition, the output buffer ( 17 ) in  FIG. 4  may be disposed to convert levels of CS (Ship Select) signal, RD (READ) signal and WR (WRITE) signal outputted from the MPU ( 11 ) to levels recognizable by the memory ( 12 ). When the MPU ( 11 ) reads data from the memory ( 12 ), and when the input buffer ( 13 ) is enabled using the RD signal because the RD signal is changed to LOW, and effective data is loaded on a bus after several clicks, the MPU ( 11 ) has to receive ineffective data due to delay generated in the course of passing the input buffer ( 13 ). 
         [0049]    In order to overcome the disadvantage thus described, the present disclosure proposes a bidirectional transmission/reception method reading and writing the data between devices having mutually different operating voltages. Particularly, the present disclosure is applicable to data transmission/reception between an MPU and a memory in PLC each having a different operating voltage, and it should be apparent to the skilled in the art that the present disclosure may be applicable to other fields than the PLC. 
         [0050]      FIG. 6  is a data flowchart during memory read by using an address signal according to the present disclosure, and  FIG. 7  is a timing diagram during memory read by using an address signal according to the present disclosure. 
         [0051]    Now, memory read process will be explained using an address signal according to the present disclosure with reference to  FIGS. 6 and 7 . 
         [0052]    Reference numeral  110  in  FIG. 6  is an MPU, which is connected to a memory ( 120 ) to transmit data to the memory ( 120 ), or to receive the data from the memory ( 120 ). At this time, the operating voltages of the MPU ( 110 ) and the memory ( 120 ) are mutually different, such that a data input buffer ( 130 ) and a data output buffer ( 140 ) configured to convert a voltage level of data transmitted and received between the MPU ( 110 ) and the memory ( 120 ) are interposed between the MPU ( 110 ) and the memory ( 120 ). 
         [0053]    Furthermore, an access signal output buffer ( 150 ) may be interposed between the MPU ( 110 ) and the memory ( 120 ), where the access signal output buffer ( 150 ) is configured to convert a voltage level of an access signal for output to access to the memory ( 120 ) in order to allow the MPU ( 110 ) to read data, or to write the data to the memory ( 120 ). 
         [0054]    Hereinafter, a signal outputted by the access signal output buffer ( 150 ) is defined as a memory access signal. 
         [0055]    That is, the data input buffer ( 130 ) may receive data from the memory ( 120 ) and convert the data to a voltage level of data recognizable by the MPU ( 110 ) and output the voltage level to the MPU ( 110 ), and the data output buffer ( 140 ) may receive the data from the MPU ( 110 ), convert the data to a voltage level of data recognizable by the MPU ( 110 ) and output the voltage level to the memory ( 120 ). 
         [0056]    Meantime, the access signal output buffer ( 150 ) may convert a voltage level of an access signal outputted for the MPU ( 110 ) to access to the memory ( 120 ) to a voltage level recognizable by the memory ( 120 ) and output the voltage level to the memory ( 120 ). 
         [0057]    Meanwhile, a first OR gate ( 160 ) may be interposed between the MPU ( 110 ) and the data input buffer ( 130 ), where the first OR gate ( 160 ) may receive a CS (Chip Select) signal and an address signal (CA: Chip Address) outputted from the MPU ( 110 ) and output an enable signal (INCS) to the data input buffer ( 130 ). 
         [0058]    Furthermore, a second OR gate ( 170 ) may be interposed between the MPU ( 110 ) and the data output buffer ( 140 ), where the second OR gate ( 170 ) may receive a CS (Chip Select) signal and a WR (WRITE) signal outputted from the MPU ( 110 ) and output an enable signal (OUT_CS) to the data output buffer ( 140 ). 
         [0059]    At this time, the MPU ( 110 ) may output a level “0” as an address signal in order to read data from the memory ( 120 ) and output a level “1” as address signal in order to write the data to the memory ( 120 ). Thus, when the address signal (CA) outputted from the MPU ( 110 ) is level “0”, the first OR gate ( 160 ) may output a level “0” as an activation signal in order to activate the data input buffer ( 130 ). Furthermore, when the address signal (CA) outputted from the MPU ( 110 ) is level “1”, the first OR gate ( 160 ) may output a level “1”, whereby the data input buffer ( 130 ) is not activated. 
         [0060]    For example, when an address area ‘O×0200 0000˜0×02FF FFFF’ is divided into read area (‘0×0200 0000˜0×027F FFFF’) and write area (‘0×0280 000˜0×02FF FFFF’), and an uppermost bit of each area is allocated by address signal (CA), the uppermost bit is always ‘0’ during reading, and the uppermost bit is always ‘1’ during write. 
         [0061]    In case of 16 M memory, an address #23 bit may be used as an input of the first OR gate ( 130 ) configured to output an activation signal (IN_CS) for activating the data input buffer ( 130 ). For example, when the MPU ( 110 ) intends to read data of 0×1000 address in the memory ( 120 ), data of 0×000 address can be read using as ‘0×200 1000’. 
         [0062]    As noted from  FIG. 7 , because the activation signal (IN_SS) is ‘LOW’ at a time of reading data, the data input buffer ( 130 ) is activated, whereby data (RAM DATA) outputted from the memory ( 120 ) is extracted as DATA BUS, and data transmission/reception can be performed without any data loss. 
         [0063]    Although the method for transmitting and receiving data between an MPU and a memory in PLC according to the exemplary embodiments of the present disclosure has been explained, the present disclosure is not limited thereto, and various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to limit the examples described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. 
         [0064]    Thus, the above-mentioned method for transmitting and receiving data between an MPU and a memory in PLC according to the exemplary embodiment of the present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein. Thus, it is intended that embodiment of the present disclosure may cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.