Abstract:
A memory device is disclosed, in which the operation of selecting the next line and relevant column addresses is unnecessary, thereby improving the data-writing/reading speed in comparison with the conventional DRAM. The memory device comprises a memory cell comprising at least two banks; and a line-address counting section for making a designated line of one of the banks active, wherein before reading or writing operation of data of the designated line is finished, the line-address counting section makes the next designated line of another bank active.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a memory device, in particular, to a DRAM (dynamic random access memory) used as a main memory in a computer or the like. 
     This application is based on Patent Application No. Hei 10-365556 filed in Japan, the contents of which are incorporated herein by reference. 
     2. Description of the Related Art 
     In consideration of the manufacturing costs and so on, DRAMs are generally used as the main memory of a computer or the like. In the operation of continuously reading or writing internal data of the DRAM, a command used for such a continuous operation is set in advance in the DRAM, a line address is selected, and then column addresses are selected. In order to continuously read or write the data of the next line, a similar operation is necessary, that is, the address signal of the next line must be selected, and then the addresses of the relevant columns must be selected. 
     In addition, a dedicated memory device in which the above-explained continuous reading/writing operation is possible is known; however, in such a device, the speed of reading or writing data is important and thus the random access function is impossible. That is, in the conventional memory device, the random access function and the continuous reading/writing function (of the line and column addresses) are incompatible. 
     As described above, in the operation of continuously reading or writing internal data in the DRAM, a command assigned to such a continuous operation is set in advance in the DRAM, a line address is selected, and then column addresses are selected, thereby starting the continuous reading or writing operation. 
     If it is assumed that line address A is selected, after the data of the last column in the designated line of address A is read or written, the data of the first column of the next line of address A+1 is continuously read or written. At this line shift, it is also necessary to select the next-line address A+1 and the relevant column address, that is, the time for selecting the above line address A+1 and the column address is necessary, so that it is very difficult to further improve the data reading/writing speed. 
     SUMMARY OF THE INVENTION 
     In consideration of the above circumstances, an objective of the present invention is to provide a memory device in which when the data of the next address is continuously read or written, the operation of selecting the next line and relevant column addresses is unnecessary, thereby improving the data-writing/reading speed in comparison with a conventional DRAM. 
     Therefore, the present invention provides a memory device comprising: 
     a memory cell comprising at least two banks; and 
     a line-address counting section for making a designated line of one of the banks active, wherein before a reading or writing operation of data of the designated line is finished, the line-address counting section makes the next designated line of another bank active. 
     In the above structure, the line-address counting section may consist of line address counters provided corresponding to each bank. 
     The above memory device may further comprise column address counters, provided corresponding to each bank, for making columns of the relevant bank active. 
     Additionally, the memory device may further comprise a bank selecting switch for selecting one of the banks, wherein when the counting operation of the column address counter provided for a bank is finished, the bank selecting switch switches the current bank and selects another bank, and another column address counter provided for the selected bank starts counting. 
     According to the present invention, it is possible to omit the time necessary for selecting the following line and relevant column addresses, and thus the data reading/writing speed can be improved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the structure of the memory device as an embodiment according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, the memory device as an embodiment according to the present invention will be explained in detail with reference to the drawings. 
     FIG. 1 is a block diagram showing the structure of the memory device of the embodiment. 
     In FIG. 1, the memory device comprises command decoder  2  for decoding the refresh, write, and read commands, which are used in the conventional DRAM, and a command of a continuous read/write operation with respect to a series of line addresses; mode register  4  for providing each command decoded by the command decoder  2 ; address buffer  6  for receiving an address sent from an external device; clock buffer  8  for receiving the reference clock (of this memory device) sent from an external device and providing a clock signal to each block of the memory device; line address counters  10   a  and  10   b  for automatically generating necessary line addresses; column address counters  12   a  and  12   b  for automatically generating necessary column addresses; memory-cell banks  14   a  and  14   b ; and I/O buffer  16  for inputting/outputting data from/to an external device. 
     The memory-cell banks  14   a  and  14   b  are independent of each other. That is, basically, the contents stored in bank  14   a  do not relate to those stored in bank  14   b . The memory structure of these banks is, for example, 1024 lines×1024 columns. 
     Reference numeral  18  indicates a bank selecting switch for choosing one of memory-cell banks  14   a  and  14   b  to be connected. 
     Below, the operation of the memory device of the present embodiment will be explained. 
     First, the reference clock is input from an external device into the memory device, and the clock buffer  8  receives this reference clock. This clock signal is output via signal line L 1  to command decoder  2 , address buffer  6 , and I/O buffer  16 . The internal operation of the memory device of the present embodiment is performed based on this reference clock. 
     The command decoder  2  receives the command of a continuous reading/writing operation (with respect to a series of line addresses) from an external device, and sends this command via signal line L 2  to mode register  4 . When the command is set in the mode register  4 , the continuous read/write command becomes effective inside the memory. 
     Next, an initial address with respect to the continuous reading/writing operation is input into the address buffer  6 , which is then input via signal line L 3  into line address counters  10   a  and  10   b  and column address counters  12   a  and  12   b , so that the top line address and top column address are determined. 
     The command set and stored in the mode register  4  is then output via signal lines L 4   a  and L 4   b  to the line address counters  10   a  and  10   b , and after this operation, these line address counters automatically generate suitable line addresses. The generated line addresses are output via signal lines L 5   a  and L 5   b  to memory-cell banks  14   a  and  14   b.    
     The address request to the memory-cell banks  14   a  and  14   b  is sent using the interleave method. 
     The command from the mode register  4  is output via signal lines L 6   a  and L 6   b  into column address counters  12   a  and  12   b , so that these column address counters  12   a  and  12   b  automatically generate suitable column addresses after this. 
     The above column addresses are output via signal lines L 7   a  and L 7   b  into memory-cell banks  14   a  and  14   b.    
     When a top line address and a top column address are selected, the column address is automatically generated by the column address counters  12   a  and  12   b  and the address processing operation is executed. 
     Here, it is assumed that the bank selecting switch  18  is connected to the memory-cell bank  14   a . When the memory-cell bank  14   a  is selected as this, the line address counter  10   a  makes the designated line active, and the column address counter  12   a  counts the column addresses in turn, so that the address counting operation of the column address counter  12   a  progresses. Before the last column address in the current line is counted, the line address counter  10   b  is activated so as to make the next line active, in which the data continuous to those of the currently designated line of bank  14   a  are stored. 
     For example, if a series of data are stored in the order of the first line of bank  14   a , the first line of bank  14   b , the second line of bank  14   a , the second line of bank  14   b , . . . , when the 100th line is made active by the line address counter  10   a , the address counter  10   b  then makes the 100th line of bank  14   b  active. 
     That is, in the present embodiment, before the column address counter  12   a  counts the last-column address of the current line, the line address counter  10   b  is operated so as to make the next-designated line of bank  14   b  active. Here, the timing of making the line active is, for example, when the column address counter  12   a  counts the address of a column located approximately 5 columns earlier than the last column. 
     When the column address counter  12   a  finally counts the address of the last column, the bank selecting switch  18  is operated so as to switch the connected bank from  14   a  to  14   b , and simultaneously, the column address counter  12   b  starts counting. 
     As described above, the designated line of bank  14   b  has already been made active by the line address counter  10   b ; thus, when the column address counter  12   b  starts the counting, the relevant stored data can be read or written, that is, the continuous reading or writing operation from bank  14   a  to bank  14   b  is immediately executed. 
     The switching operation from bank  14   b  to  14   a  is similarly performed, that is, before the counting of the column address counter  12   b  is finished, the line address counter  10   a  makes the next designated line of bank  14   a  active. 
     The bidirectional read/write data transmission is performed via line L 8  between the banks  14   a  and  14   b  and the I/O buffer  16 . 
     According to the above-explained memory device as an embodiment of the present invention, when the data of a series of line addresses of a DRAM are continuously read or written, the conventional address designating operation is necessary only for the top line and column addresses, and unnecessary for the following addresses by using the line address counter  10   b  and the column address counter  12   b  in the DRAM. Therefore, in the continuous data reading/writing operation, it is possible to omit the time necessary for selecting such following line and column addresses, thereby improving the data reading/writing speed.