A dynamic random access memory (DRAM) device is formed on a semiconductor substrate, the device having an array of memory cells which are divided in several sub-arrays. The device has memory blocks each containing one of the sub-arrays, a word decoder and column decoder. Each of the memory blocks is selected independently to perform an access operation and refresh operation. As long as different memory blocks are selected for the respective operations, both operations are performed in parallel, however, when the same memory block is selected for both operations, namely, double selection, a comparison circuit detects the double selection and gives priority to one of the operations. The operation selected thus, preferentially performed. Usually, the refresh operations is then performed. However, in order to decrease the "busy ratio" of the device, the access operation is performed preferentially. Further, a complicated operation for priority selection may be performed according to a predetermined schedule memorized in a priority providing means. In addition, a common word bus line is proposed for accessing each of the memory blocks, namely, each sub-arrays, in order to reduce the number of common word lines for realizing a further high packing denisty of the DRAM device. This common bus line is also applicable to other devices such as a static RAM.
A memory device is provided including a plurality of memory arrays and peripheral circuits. For example, in a dynamic RAM the peripheral circuitry will include row address decoders, column address decoders, sense amplifiers and main amplifiers disposed in such a manner as to correspond to the memory arrays, respectively. The desired row address decoders, column address decoders, sense amplifiers and main amplifiers are selectively operated in accordance with a common array selection signal generated on the basis of at least part of row address signals. Accordingly, only the row address decoders, column address decoders, sense amplifiers and main amplifiers corresponding to the memory array containing the designated memory cells are operated selectively in accordance with the common array selection signal. It is thus possible to reduce power consumption of the dynamic RAM and to simplify the structure of the peripheral circuits and wirings.
A semiconductor memory device includes: a memory cell array constituted of a plurality of memory cell array units; transfer gates inserted in bit lines between the adjacent memory cell array units; a first and a second column decoders connected to both ends of bit lines in which the transfer gates are inserted; a row decoder connected to word lines of the memory cell array. The row decoder is adapted to be divided selectively in two parts; and two sets of row/column addresses are supplied to the column decoders and the row decoder. Therefore, simultaneous separate accesses to the memory cell array are carried out by the two sets of row/column addresses.
A semiconductor device includes a memory cell array which is divided into four blocks, specifically, a block (0), a block (1), a block (2), and a block (3). In this semiconductor device, during a period in which the data read or write is performed in one block, refreshing is executed in all of the other blocks.
A memory device is provided including a plurality of memory arrays and peripheral circuits. For example, in a dynamic RAM the peripheral circuitry will include row address decoders, column address decoders, sense amplifiers and main amplifiers disposed in such a manner as to correspond to the memory arrays, respectively. The desired row address decoders, column address decoders, sense amplifiers and main amplifiers are selectively operated in accordance with a common array selection signal generated on the basis of at least part of row address signals. Accordingly, only the row address decoders, column address decoders, sense amplifiers and main amplifiers corresponding to the memory array containing the designated memory cells are operated selectively in accordance with the common array selection signal. It is thus possible to reduce power consumption of the dynamic RAM and to simplify the structure of the peripheral circuits and wirings.
A semiconductor memory device and method for its operation are disclosed. The memory device uses refresh-type memory cells, but operates within the same timing parameters as an SRAM. A refreshing operation and a successful read/write operation can both be performed in a read/write cycle, with zero write recovery time. But if the read/write cycle goes long, multiple refreshing operations can also be performed during the read/write cycle. Thus the device operates with no maximum write cycle time limitation. In the disclosed method, an external write command causes the device to store the write address and data to registers instead of to the memory cell array. When the external write command signals that data is present, zero write recovery time is needed, since the registers require no address setup time. Because the memory cell array is not involved in this transaction, refresh operations can proceed as needed during the external write command, no matter how long the external write takes to complete. At a convenient time after the end of the external write command (e.g., during the next external write command), a short pulsed write operation transfers the data to the memory cell array.
