Abstract:
In the semiconductor integrated circuit of the present invention, write and read operation are successively implemented in which a manner that read addresses are inputted after write addresses are inputted and read data is read from a sense amplifier starting from the next cycle after all the data have been written to the sense amplifier.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method of controlling a semiconductor storage circuit, more particularly to a method of controlling a continuous write and read operation to be implemented in a pipeline circuit. 
     2. Description of the Prior Art 
     Recently, with the advance of the operation speed of a CPU, there has been an increasing demand for a semiconductor storage device which operates at high speed. 
     However, because of a physical limit against the minute fractionization of the device manufacturing process or an increased chip size due to desired enlargement of the capacity, it can not be said that the demand for the high speed semiconductor storage device has been sufficiently satisfied. 
     Therefore, as a means for solving the above problem, there is proposed DRAM which has an internal pipeline structure. 
     FIG. 1 is a circuit diagram in a block form showing a conventional DRAM which has a pipeline structure. In the block diagram, a data-in latch 40 comprises a write buffer 41 which receives write data from a terminal DO, a D-F/F circuit 42 for latching an output of the write buffer 41 with the timing of an internal clock signal ICLK1, a D-F/F circuit 43 for latching an output of the D-F/F circuit 42 with the timing of an internal clock signal ICLK2, and a write amplifier 44 for receiving an output of the D-F/F circuit 43 and outputting it to a R/W bus 80. A buffer 61 outputs data on the R/W bus 80 to a sense amplifier 60, and a buffer 62 receives an output of the sense amplifier 60 to output it to the R/W bus 80. A plurality of pairs of bit lines between the sense amplifier 60 and a memory cell array 70 constitutes a write/read path. The memory cell array 70 includes a plurality of memory cells disposed in the directions of rows and columns in a form of array. A data-out latch 50 comprises a buffer 51 which receives data on the R/W bus 80, a D-F/F circuit 52 for latching an output of the buffer 51 with the timing of an internal clock signal ICLK3, and a data-out buffer 53 for receiving an output of the D-F/F circuit 52 and transmitting the received output to the terminal DO as read data. A column address latch 10 comprises column address buffers 11 which receive address signals A0, A1, A2, ---, An from the outside, respectively, and a D-F/F circuit 12 for latching an output of the column address buffer 11 with the timing of the internal clock signal ICLK1. A burst counter 120 generates column addresses based on column addresses latched in the D-F/F circuit 12. The number of column addresses to be generated equals to the burst length. A column decoder 20 is supplied with outputs of the burst counter 12. A column address latch 30 comprises inverter IV1 and IV2 and an N channel type transistor Trl which receives the internal clock signal ICLK2 on its gate, and receives an output from the column decoder 20 to output a column switch signal. Row address buffers 90 receive address signals A0, A1, A2, . . . , An from the outside, respectively. A row decoder 100 receives and decodes the outputs of row address buffers 90 and drives word lines 110 connected with the memory cell 70. 
     Write operation of DRAM shown in FIG. 1 will next be described also with reference to FIG. 2. 
     In FIG. 2, when, in a cycle C1, a combination of data supplied to input terminals is selected as an active command at the leading edge of the external clock signal CLK from the outside, then the data on address terminals at that time are latched in the row address buffers 90 as row addresses and are decoded to select a word line. 
     Next, in a cycle C3, when a combination of data supplied to input terminals is Selected as a write command, the data A1 on the address terminal at that time is latched in the D-F/F12 with the timing of the internal clock signal ICLK1 as a column address. When the write command is inputted, the internal clock signals ICLK1, ICLK2, and ICLK3 are generated by an internal clock generation circuit which is not shown. The internal clock signal ICLK1 becomes a high level only one time in the cycle C3 in which the write command is inputted. The internal clock signal ICLK2 becomes a high level in a cycle C4 and C5 delayed from the write command by one cycle and two cycles, respectively. The internal clock signal ICLK3 becomes a high level only one time in the cycle C5 delayed from the write command by two cycles. When the internal clock signal ICLK1 becomes a high level state only one time in the cycle C3, the address data A1 is transmitted to the column decoder 20 to be latched therein. 
     Next, when the internal clock signal ICLK2 becomes a high level only one time in the cycle C4, the address data A1 is transmitted to the column address latch 30 and latched therein during the time period of the high level state. On the other hand, data DIN inputted from the terminal DO as write data in the cycle C3 is transmitted by the internal clock signals ICLK1 and ICLK2 of the high level state and is written to the sense amplifier 60 through the R/W bus 80 in the cycle C4. Thereafter, the data DIN is written in the memory cell from the sense amplifier 60 in a cycle C5. 
     The internal clock signal ICLK2 resets the address data latched in the column address latch 30 in the cycle C5. Also a precharge command for resetting a row address can first be inputted in the cycle C5 in which data is written into the memory cell. 
     Read operation of DRAM shown in FIG. 1 will next be described with reference to FIG. 3. 
     When a read command is inputted in a cycle C3, data A2 on the address terminal at this time is latched in the column address buffer 10 as a column address in the same manner as in the write time, and internal clock signals ICLK1, ICLK2, ICLK3 are generated in the same way as in the write operation. When the internal clock signal ICLK1 becomes a high level only one time in the cycle C3, the address data A2 is transmitted to the column decoder 20 and latched therein. 
     Subsequently, when the internal clock signal ICLK2 becomes a high level in a cycle C4, the column address latch 30 is selected to transmit the address data A2 to the column address latch 30 during this cycle and then the address data A2 is latched in the column address latch 30. When the column address latch is selected, the data in the sense amplifier 60 is transmitted through the R/W bus 80 and latched by the data-out latch 50 in the cycle C4. 
     Following which, when the internal clock signal ICLK3 becomes a high level in the cycle C5, the data latched in the data-out latch 50 is outputted to the terminal DO. 
     In the read operation, the data stored in the sense amplifier 60 is read in the cycle C4, and hence it becomes possible to input a precharge command in the cycle C4. 
     The operations shown in FIG. 2 and FIG. 3 are operations with the burst length being equal to 1, and in which only one address is accessed for one write command or one read command and also the data is inputted or outputted only once for the command. The burst length is determined by the mode register set operation before the active command is inputted. 
     FIG. 4 shows the write operation in the case of burst 10 length being equal to 4. When a write command is inputted in the cycle C3 and address data A1-1 is inputted, then address data A1-2, A1-3, A1-4 are produced in the cycles C4, C5, C6, respectively, by means of the internal burst counter 120. At this time, the internal clock signals ICLK1, ICLK2, ICLK3 are energized 4, 5, 6 and times, respectively, and 4-bit data is written thereby. Since 1-bit data is written in one cycle during the burst operation, when the burst length is 4, writing of 4-bit data is completed in six cycles which starts from the cycle for inputting the write command. 
     With this conventional method of controlling the semiconductor storage circuit, three clock cycles are required from the input of the write command to data writing in a memory cell and three clock cycles are also required from the input of the read command to data reading from the memory cell. Therefore, if write, and read operations are each operated for 1 bit on the same word line, at least six clock cycles are needed, yielding poor efficiency of a pipeline circuit. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention is to provide a method of controlling a semiconductor storage circuit, which is capable of effectively utilizing a circuit of a pipeline structure in the semiconductor storage circuit. 
     In order to achieve the above object, according to the present invention, there is provided a method of controlling a semiconductor storage circuit which comprises: a memory cell array including a plurality of memory cells disposed in the directions of rows and columns in a form of array, a plurality of pairs of bit lines connected with these memory cells, a plurality of word lines connected with these memory cells; a sense amplifier connected to the ends of each pair of bit lines for amplifying an electric potential difference between two lines of the pair of bit lines in response to an activation signal; row address buffers and column address buffers which receive address signals; a row decoder for decoding output signals of the row address buffers and driving the word line connected with the memory cells; a column decoder for decoding output signals of the column address buffers and driving a pair of bit lines connected with the memory cells; a data amplifier for receiving an output signal of the sense amplifier selected by the column decoder and amplifying the received signal at the time when data is read from the memory cell array; a data-out buffer for receiving an output signal of the data amplifier and outputting the received signal to an input/output terminal; a write buffer for receiving a write data signal supplied from the input/output terminal at the time when the data is written in the memory cell array; a write amplifier for receiving an output signal of the write buffer and outputting write data to the memory cell selected by the row and column decoders, respectively; and latch circuit disposed immediately before or immediately after the column address buffers, the column decoders, the data-out buffer, the write buffer and the write amplifier, respectively and controlled by an external clock signal; the method comprising the steps of: 
     inputting an active command to determine a row address; 
     inputting a write command; 
     latching the column address determined through the input of said write command in said latch circuit disposed immediately before or immediately after said column address buffer, and latching a write data inputted from said input/output terminal in said latch circuit disposed immediately before or immediately after said write buffer, in response to a first internal clock signal synchronized with the external clock signal in the cycle when said write command was inputted; 
     latching the output signal of said column address buffer in said latch circuit disposed immediately before or immediately after said column decoder and latching the output of said write buffer in said latch circuit disposed immediately before or immediately after said write amplifier, in response to a second internal clock signal synchronized with the external clock signal in the cycle next to the cycle when said write command was inputted; 
     inputting a read command in the cycle next to the cycle when said write command was inputted; 
     latching the column address determined through the input of said read command in said latch circuit disposed immediately before or immediately after said column address buffer, in response to the first internal clock signal synchronized with the external clock signal in the cycle when said read command was inputted; 
     latching the output signal of said column address buffer in said latch circuit disposed immediately before or immediately after said column decoder, in response to the second internal clock signal synchronized with the external clock signal in the cycle next to the cycle when said read command was inputted; and 
     latching the output signal of said data amplifier in said latch circuit disposed immediately before or immediately after said data-out buffer, in response to a third internal clock signal synchronized with the external clock signal in the cycle next to the cycle when said read command was inputted. 
     In the semiconductor storage circuit further comprising a burst counter for generating a column address/column addresses depending on the column address inputted from the outside, synchronized with the external clock, it is practical, after the row address is determined by an active command and the word line is selected, to input a write command and further input a read command with the timing of the external clock in a cycle which follows immediately after the cycle in which all column addresses necessary for write have been generated by the burst counter. 
     Further, the semiconductor storage circuit comprising a read/write bus composed of at least a part of the wiring provided between the latch circuit disposed immediately before or immediately after the write amplifier and the sense amplifier and at least a part of the wiring provided between the latch circuit disposed immediately before or immediately after the data-out buffer and the sense amplifier, the semiconductor storage circuit may further be structured such that the read data is transmitted through the read/write bus in the cycle synchronized with the external input clock which follows immediately after the cycle in which the write data has been transmitted through the read/write bus. 
     In the present invention, a semiconductor storage circuit is controlled such that write address are inputted before read addresses have been inputted, and read data can be read from a sense amplifier starting from the cycle which follows immediately after the cycle in which all of the write data has been inputted in the sense amplifier. Therefore, the number of cycles to be required for performing write and read operation on the same word line can be decreased, thereby enabling to effectively use a circuit of a pipeline structure. 
     The above and other objects, features, and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a circuit diagram of a conventional DRAM in a block form. 
     FIG. 2 is a timing chart showing the write operation of DRAM shown in FIG. 1. 
     FIG. 3 is a timing chart showing the read operation of DRAM shown in FIG. 1. 
     FIG. 4 is a timing chart showing the write operation of DRAM shown in FIG. 1. 
     FIG. 5 is a timing chart showing a first embodiment of the present invention. 
     FIG. 6 is a timing chart showing a second embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention, in which the burst length is set to 1 will be explained hereinafter with reference to FIGS. 1 and 5. 
     When an active command is inputted in a cycle C1, address data in the cycle C1 is latched in the row address buffer 90 as a row address and a word line is selected corresponding thereto by the row decoder. 
     Next, when a write command is inputted in a cycle C3, address data A1 is latched in the column address buffer 11 as a column address. When an internal clock signal ICLK1 becomes a high level in the cycle C3, the address data A1 is transmitted to the D-F/F12 and latched therein. 
     Subsequently, when an internal clock signal ICLK2 becomes a high level in a cycle C4, the column address latch 30 is selected. Therefore, the address data A1 is transmitted to the column address latch 30 to be latched therein during a time period of this high level state of the internal clock signal ICLK2. At the same time, when a read command is inputted in the cycle C4, an address data A2 is latched in the D-F/F12. 
     When the internal clock signal ICLK2 becomes a high level in a cycle C5, the address data A2 is transmitted to the column address latch 30 to be latched therein. 
     On the other hand, when the internal clock signal ICLK2 becomes a high level in a cycle C4, data DIN inputted from the terminal DO as write data in the cycle C3 is latched in the D-F/F43 and is supplied to the sense amplifier 60 through the write amplifier 44, the R/W bus 80 and the buffer 61 in the cycle C4 to be written into a memory cell in the cycle C5. 
     When the internal clock signal ICLK3 becomes a high level in a cycle C5, output data DOUT outputted in response to the read command which is inputted in the cycle C4 is transmitted from the sense amplifier 60 through the R/W bus 80 to the data-out latch 50 to be latched therein in the cycle C5 and then outputted to the terminal DO in a cycle C6. 
     Since the operation of the sense amplifier 60 is finished in the cycle C5, a precharge command can be inputted in this cycle C5 successively. 
     A second embodiment of the present invention, in which the burst length is set to 2, will be explained hereinafter with reference to FIGS. 1 and 6. 
     An active command is inputted in a cycle C1 in the same way as in the burst length being equal to 1. When a write command is inputted in a cycle C3 and the first internal clock signal ICLK1 becomes a high level, an address data A1-1 is latched in the column address latch 10 as a column address. In a next cycle C4, when the internal clock signal ICLK1 becomes a high level, an address data A1-2 generated by the burst counter 120 is latched in the column decoder 20. In cycles C4 and C5, when the second internal clock signal ICLK2 becomes a high level, column address latches 30 of the address data A1-1, A1-2 are selected to latch the address data therein, respectively. 
     When a read command is inputted in the cycle C5 and the first internal clock signal ICLK1 becomes a high level, an address data A2-1 is latched in the column address latch 10 as a column address in the same way as above. When the second internal clock signal ICLK2 becomes a high level in a cycle 6, then address data A2-2 is generated by the burst counter 120 and latched in the column decoder 20 as a column address. When the second internal clock signal ICLK2 becomes a high level in cycles C6, C7, column address latches 30 of the address data A2-1, A2-2 are selected and the address data are latched in the selected column address latch. 
     When the first internal clock signal ICLK1 becomes a high level, write data DIN-1 and DIN-2 are inputted in the cycles C3 and C4, respectively. When the second internal clock signal ICLK2 becomes a high level, then data DIN-1 and DIN-2 are latched in the D-F/F43 and inputted into the sense amplifier 60 through the write amplifier 44, the R/W bus 80 and the buffer 1 in cycles C4 and C5, respectively, and further written in the memory cell in the cycles C5 and C6, respectively. 
     When the third internal clock signal ILK3 becomes high a high level in the cycle C6 and C7, the data DOUT-1 and DOUT-2 which are read from the memory cell array 70 are transmitted from the sense amplifier 60 through the buffer 62, the R/W bus 80 to the data-out latch 50 to be latched therein in a cycle C6 and C7, respectively, and further outputted to the terminal DO in cycles C7 and C8, respectively. 
     A precharge command can be inputted in the cycle C7 when reading of the data from the sense amplifier 60 is finished in the cycle C7. 
     While a preferred embodiment of the invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.