Low pin count - wide memory devices using non-multiplexed addressing and systems and methods using the same

• US 5,600,606 A
• Filed: 03/07/1996
• Issued: 02/04/1997
• Est. Priority Date: 08/31/1995
• Status: Expired due to Term

• Current Assignee: Foothills IP LLC
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Rao, G. R. Mohan
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): PHAN, TRONG Q
• Application Number:
  US08/612,113
• Time in Patent Office: 334 Days
• Field of Search: 365/233, 365/189.05, 365/193, 365/230.08, 365/238.5
• US Class Current: 365/233.1
• CPC Class Codes: G11C 5/066 Means for reducing external access-lines for a semiconductor memory clip, e.g. by multiplexing at least address and data signals

Abstract

A method of operating a memory device including a plurality of data/address input/output terminals, an array of memory cells and circuitry for accessing selected ones of the memory cells in response to received address bits. At least one row address bit and at least one column address bit are substantially simultaneously input during an address cycle, at least one of the address bits being input through a selected one of the multiplexed terminals. The memory cells addressed by the row and column bits are then accessed through selected ones of the multiplexed terminals during a data access cycle.

Claims

1. A method of operating a memory device including a plurality of multiplexed data/address input/output terminals, an array of memory cells, and circuitry for accessing selected ones of the memory cells in response to received row and column address bits, the method comprising the steps of:

substantially simultaneously inputting said row address bit and column address bit during an address cycle, at least one of said row and column address bits input through a selected one of the multiplexed terminals; and

accessing ones of the memory cells addressed by the row and column bits through selected ones of the multiplexed terminals during a data access cycle.

2. The method of claim 1 and further comprising the step of inputting an additional column address bit to access at least one additional cell along a row addressed by the row address bit.

3. The method of claim 2 wherein the memory device further comprises at least one dedicated address terminal and wherein said step of inputting an additional column address bit comprises the step of inputting the additional column address bit through the dedicated address terminal.

4. The method of claim 1 wherein the memory device is controlled by a row address strobe and the address cycle occurs during a period when the row address strobe is in a logic high state and the data access cycle occurs during a period when the row address strobe is in a logic low state.

5. The method of claim 3 wherein the at least one additional column address bit is input in response to a column address strobe.

6. The method of claim 5 wherein the least one additional column address bit is input during the period when the row address strobe is in a logic low state.

7. The method of claim 1 wherein the memory device comprises a synchronous memory device and the method further comprises the step of inputting command information during the address cycle.

8. A method of operating a random access memory comprising the steps of:

during a precharge period, substantially simultaneously inputting row and column address bits, at least some of said row and column address bits input through a plurality of multiplexed data/address input/output terminals; and

during an active period,performing a random access to memory cells addressed by the input row and column address bits through the multiplexed terminals.

9. The method of claim 8 wherein a row address strobe times the precharge and active periods, the row address strobe being in a first logic state during the precharge period and in a second logic state during the active period.

10. The method of claim 8 and further comprising the step of performing a page access following the random access, said step of performing a page access comprising the substeps of:

inputting a plurality of additional column address bits in response to a column address strobe transitioning from a first logic state to a second logic state; and

accessing a page addressed by the additional column address bits from the row addressed during the precharge cycle.

11. The method of claim 10 wherein the memory includes dedicated address terminals and said step of inputting additional column address bits comprises the step of inputting at least some of the additional column address bits through the dedicated address terminals.

12. The method of claim 8 and further comprising the step of decoding the column address bits received during the precharge period during the precharge period.

13. The method of claim 8 wherein the memory comprises a synchronous memory and the method further comprises the step of inputting at least one command bit during the precharge period.

14. The method of claim 10 wherein said step of performing a page access further includes the substep of inputting at least one command bit identifying a type of access being performed.

15. A random access memory comprising:

a plurality of terminals for receiving substantially simultaneously row and column address bits during an address cycle, at least some of said plurality of terminals comprising multiplexed terminals for exchanging data during a data access cycle;

an array of rows and columns of memory cells; and

addressing circuitry for accessing locations within said array in response to received row and column address bits.

16. The memory system of claim 15 wherein said terminals comprise pins.

17. The memory system of claim 15 wherein said random access memory comprises a synchronous dynamic random access memory.

18. The memory system of claim 15 and wherein said plurality of terminals includes at least one dedicated data terminal for exchanging data with an external device.

19. The memory system of claim 15 and wherein said plurality of terminals includes at least one dedicated address terminal for receiving an address bit an external device.

20. The memory system of claim 19 wherein said at least one dedicated address pins comprises at least one column address pin.

21. A memory system comprising:

a non-multiplexed address bus;

a data bus; and

a random access memory comprising;

a plurality of terminals for receiving substantially simultaneously row and column address bits presented on said non-multiplexed address bus during an address cycle, at least some of said plurality of terminals comprising multiplexed terminals for exchanging data with said data bus during a data access cycle;

an array of rows and columns of memory cells; and

addressing circuitry for accessing locations within said array during said data access cycle in response to received row and column address bits.

22. The system of claim 21 wherein said random access memory comprises a synchronous dynamic random access memory.

23. The system of claim 21 where in said random access memory comprises an asynchronous dynamic random access memory.