User selectable banks for DRAM

Abstract

A memory device includes a configurable array of memory cells. A number of array banks is configured based upon data stored in a mode register or decoded by logic circuitry. The memory device remains a full capacity memory, regardless of the number of array banks. Memory address decoding circuitry is adjusted to route address signals to or from a bank address decoder based upon the number of array banks selected.

Description

FIELD OF THE INVENTION

The present invention relates generally to memory devices and in particular the present invention relates to memory bank addressing.

BACKGROUND OF THE INVENTION

Memory devices such as dynamic random access memories (DRAM) include memory cell arrays to store data. The memory array is typically arranged in addressable rows and columns. Often, the array is also arranged in numerous addressable banks. These banks can be physically separated on the memory die and have separate access circuitry. As such, row, column and bank addresses are used to read and write to the memory.

The number of memory array banks provided in a memory device can limit data access speed of the memory. That is, a memory device that has two banks allows the second bank to begin access operations while the first array is accessed. Likewise, additional array banks increase the likelihood that requested data is stored in different banks. Because repeated accesses to the same bank fail to take advantage of the parallel bank access functionality, an increased number of banks is advantageous.

Memory device manufactures attempt to make new generations of memory devices compatible with prior memory device generations. This compatibility allows one device to be manufactured without making the prior generation obsolete. If the new generation is not compatible, two or more generations are required to support current systems and future systems. Reverse compatible memory devices having a different number of array banks has proven difficult. For example, a new memory design with eight banks has different addressing and physical layout than a four-bank memory device. As such, both four and eight bank memory devices must be manufactured.

Memory manufactures have provided options that can change the capacity of a memory to reduce power consumption. For example, the memory array and addressing can be modified to reduce storage capacity. By reducing the memory size, portions of the array can be eliminated from refresh operations. While this option reduces power consumption, it does not provide a viable option to configure a memory without reducing the memory capacity.

For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a memory device that can be configured with variable sized array banks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a memory device according to one embodiment of the present invention;

FIG. 2 is a block diagram of addressing circuitry of FIG. 1; and

FIG. 3 is a block diagram of a memory device according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific preferred embodiments in which the inventions may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the claims.

The present invention provides a memory device that can operate with a full density while changing addressing schemes. As stated above, an increased number of banks in a memory device can result in more efficient accessing of the memory array. The present invention allows a memory device to be configured to increase or decrease the number of memory array banks without changing the density of the memory. This allows the memory device to be both forward and backward compatible.

Referring to FIG. 1, a block diagram of a memory device 100 according to one embodiment of the present invention is described. The memory device includes an array of memory cells 102 that is arranged in a plurality of physical banks. It will be appreciated that the layout of the array is dependant upon the design of the memory device and the present invention is not limited to any one type of physical layout.

Address circuitry 104 is provided to access the memory cells in combination with bank 105, row 106 and column 108 decoders. A control circuit 110 is provided to perform read and write operations in response to externally provided control signals from controller 101. Bi-directional data communication with the memory array is performed by I/O circuitry 112 and read/write circuitry 114. A mode register 116 is provided to define operating modes for the memory device. The mode register is typically used to define clock latency, burst access type and burst access lengths. The mode register of the present invention is used to set the address circuitry to configure the memory device for different bank addressing. Address input connections 120 include one or more address connections that can be used as either a row or column address, or a bank address.

It will be appreciated by those skilled in the art, with the benefit of the present description, that the memory device has been simplified and that additional circuitry and features may be required. In one embodiment, the memory device is a synchronous DRAM. In yet another embodiment the memory is a DDR SDRAM. The present invention, however, is not limited to a dynamic memory, but can be any memory device having address input connections, such as SDRAM, RDRAM, Flash, DRAM, SRAM, SGRAM and the other semiconductor memories.

Referring to FIG. 2, a block diagram of the addressing circuitry 104 of FIG. 1 is further described. The mode register 116 is coupled to the address circuit to change the decoding of one or more input address signals. That is, the address signal inputs 120 provided to the memory device include bank, row and column addresses. In a four-bank memory addressing scheme less bank addresses are required than in an eight-bank memory addressing scheme. As such, one or more of the address connections have a dual purpose. When the mode register is programmed to operate as an eight-bank memory, an address input is routed through an address multiplexer circuit 130 to the bank decoding circuit. When the mode register is programmed to operate as a four-bank memory, the address input is routed through the address multiplexer circuit to the row decoding circuit 106. Thus, the memory device can be programmed to operate as either a four-bank memory with X rows per bank, or an eight-bank memory with Y rows per bank without changing the memory capacity. Again, the present invention is not limited to four or eight banks, but can be any combination of banks, rows and columns.

In an alternate embodiment, the mode register can be replaced with an external signal input and a decode circuit. Referring to FIG. 3, an external signal is provided on input 150. In one embodiment, this input signal is a one-bit binary configuration signal that is decoded by logic circuit 152. In embodiments where the array can be configured in to multiple different sizes, the input signal may be a multi-bit configuration signal. The logic circuit 152 operates in substantially the same manner as the mode register, as described above. That is, the logic circuitry is used to control the address circuitry to change the number and size of the array blocks.

CONCLUSION

A memory device has been described that includes a configurable array of memory cells. A number of array banks is configured based upon data stored in a mode register. The memory device remains a full capacity memory, regardless of the number of array banks. Memory address decoding circuitry is adjusted to route address signals to or from a bank address decoder based upon the number of array banks selected.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.

Claims

1. A system, comprising: a controller; anda memory device coupled to the controller to receive signals therefrom, and comprising: an array of memory cells, the array of memory cells selectively configurable into one of a plurality of different addressable bank configurations, each bank comprising addressable rows and columns of memory cells;a mode register; andaddress circuitry coupled to the mode register to configure the addressable banks in response to a program state of the mode register.

2. The system of claim 1 wherein the addressable banks can be configured as either four or eight banks.

3. A memory device, comprising: an array of memory cells addressable by rows and columns, the array of memory cells configurable into one of a plurality of physical bank configurations, each bank configuration having a different number of banks;a mode register containing data to configure operation of the array into one of the plurality of physical bank configurations; andaddress circuitry coupled to the mode register to configure the array in response to data in the mode register.

4. The memory device of claim 3, wherein the address circuitry further comprises: a multiplexer to route received addresses to one of a row decoder and a bank decoder depending on the state of the mode register.

5. The memory device of claim 3 wherein the address circuitry selectively routes address signal to either a row decoder or a bank decoder in response to the mode register.

6. A system, comprising: a controller; anda dynamic random access memory device coupled to the controller and comprising: an array of X memory cells;a mode register; andaddress circuitry coupled to the mode register to configure the array in response to a program state of the mode register, wherein the mode register defines a configuration of the memory array from one of a plurality of configurations of the memory array, each of the configurations comprising a different number of addressable banks.

7. The system of claim 6 wherein a first state of the mode register configures the array into Y banks each having X/Y memory cells, and a second state of the mode register configures the array into Z banks each having X/Z memory cells.

8. The system of claim 6, wherein the address circuitry further comprises: a multiplexer to route received addresses to one of a row decoder and a bank decoder depending on the state of the mode register.

9. The system of claim 6 wherein the address circuitry comprises column, row and bank address decoders.

10. The system of claim 9 wherein the address circuitry routes a selected address input signal to either the row or bank decoder in response to the mode register.

11. The system of claim 10 wherein the address circuitry comprises a multiplex circuit.

12. A system, comprising: a controller providing an input signal; anda dynamic random access memory device coupled to the controller and comprising:an array of X memory cells;a decode circuit to decode the input signal; andaddress circuitry coupled to the decode circuit to configure the array in response to a program state of the input signal, wherein the input signal defines a configuration of the array into one of a plurality of addressable bank configurations, each having a different number of addressable banks, based on a program state of the external input signal.

13. The system of claim 12 wherein a first state of the input signal configures the array into Y banks each having X/Y memory cells, and a second state of the input signal configures the array into Z banks each having X/Z memory cells.

14. The system of claim 12 wherein the address circuitry comprises column, row and bank address decoders.

15. The system of claim 14 wherein the address circuitry routes a selected address input signal to either the row or bank decoder in response to the controller input signal.

16. The system of claim 12 wherein the address circuitry comprises a multiplex circuit.

17. A memory device, comprising: an array of memory cells arranged in addressable rows and columns of memory cells;a decode circuit to decode an external input signal; andaddress circuitry coupled to the decode circuit to configure the array in response to a program state of the external input signal, wherein the input signal defines a configuration of the array into one of a plurality of addressable bank configurations, each having a different number of addressable banks, based on a program state of the external input signal.

18. The memory device of claim 17 wherein the addressable banks can be configured as either four or eight banks.

19. A dynamic random access memory comprising: an array of X memory cells;a decode circuit to decode an external input signal; andaddress circuitry coupled to the decode circuit to configure the array in response to a program state of the external input signal, wherein the input signal defines a configuration of the array into one of a plurality of addressable bank configurations each having a different number of addressable banks.

20. A method of operating a memory device comprising: receiving an external input signal at decode circuitry of the memory device; andadjusting address circuitry of the memory device in response to the decoded external input signal, wherein the address circuitry configures an array of memory cells of the memory device into a plurality of addressable banks, the bank configuration being one of a plurality of bank configurations each having a different number of addressable banks.

21. A system, comprising: a controller to provide an input signal; anda memory device coupled to the controller, the memory device comprising: an array of memory cells addressable by rows and columns, the array of memory cells configurable into one of a plurality of physical bank configurations, each bank configuration having a different number of banks;a mode register containing data to configure operation of the array into one of the plurality of physical bank configurations; andaddress circuitry coupled to the mode register to configure the array in response to data in the mode register.

22. The system of claim 21, wherein the address circuitry further comprises: a multiplexer to route received addresses to one of a row decoder and a bank decoder depending on the state of the mode register.

23. A method of configuring a memory device, comprising: providing an input signal at decode circuitry of the memory device; andconfiguring an array of memory cells of the memory device into one of a plurality of physical bank configurations, each bank configuration having a different number of banks, wherein configuring is in response to the input signal.

24. The method of claim 23, wherein the input signal is provided to address circuitry which configures the array of memory cells.

25. The method of claim 23, and further comprising: programming a mode register of the memory device with the input signal; andadjusting address circuitry of the memory device in response to the input signal, wherein the address circuitry configures the array of memory cells into one of the plurality of physical bank configurations.

26. The method of claim 23, wherein configuring the array of memory cells further comprises: adjusting address circuitry of the memory device in response to the input signal, wherein the address circuitry configures the array of memory cells into one of the plurality of physical bank configurations.