Method for accessing memory using overlapping accesses and early synchronous data transfer control

• US 6,079,001 A
• Filed: 06/04/1997
• Issued: 06/20/2000
• Est. Priority Date: 08/31/1994
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Le, Chinh H., Vauk, Gerald E. Jr.
• Primary Examiner(s): Chan, Eddie P.
• Assistant Examiner(s): KIM, HONG CHONG
• Application Number:
  US08/868,622
• Time in Patent Office: 1,112 Days
• Field of Search: 395/559, 395/800.4, 395/494, 395/496, 711/767, 711/169, 711/167, 711/170, 713/400, 713/600, 365/230.06
• US Class Current: 711/167
• CPC Class Codes: G06F 12/1441 for a range
• CPC Class Codes: G06F 13/1694 Configuration of memory controller to different memory types
• CPC Class Codes: G06F 13/4243 with synchronous protocol

Abstract

Accordingly, the present invention provides a method for synchronously accessing memory in order to improve the performance in systems which use memories with slower cores. A first address for a first memory access is provided during a first clock period. A first control signal to indicate an address phase of the first memory access is activated during the first clock period. A second control signal to indicate a data phase of the first memory access is activated during a second clock period subsequent to the first clock period. A first data element accessed by the first address is received during a third clock period immediately subsequent to the second clock period. A second address for a second memory access is provided during the third clock period. The first control signal indicating an address phase of the second memory access is activated during the third clock period.

Claims

1. A method for synchronously accessing memory, comprising the steps of:

providing a first address for a first memory access during a first clock period;

activating a first control signal indicating an address phase of said first memory access during said first clock period;

activating a second control signal indicating a data phase of said first memory access during a second clock period subsequent to said first clock period;

receiving a first data element accessed by said first address during a third clock period immediately subsequent to said second clock period;

providing a second address for a second memory access during said third clock period; and

activating said first control signal indicating an address phase of said second memory access during said third clock period.

2. The method of claim 1 wherein the step of activating said second control signal comprises the step of:

activating said second control signal during said second clock period subsequent to said first clock period by a predetermined number of wait states.

3. The method of claim 1 wherein said step of activating said first control signal comprises the step of activating a chip enable control signal.

4. The method of claim 2 wherein said step of activating said second control signal comprises the step of activating an output enable control signal.

5. The method of claim 1 further comprising the steps of:

activating a third control signal indicative of a burst data cycle in progress during said third clock period; and

receiving a second data element during a fourth clock period subsequent to said third clock period.

6. The method of claim 1 further comprising the steps of:

activating a third control signal indicative of a burst data cycle in progress during a first plurality of clock periods including said third clock period; and

receiving a plurality of burst data elements during a second plurality of clock periods subsequent to said third clock period and corresponding to said first plurality of clock periods.

7. The method of claim 1 wherein said step of providing said first address during said first clock period comprises the step of providing said first address at least a first predetermined setup time before first predetermined transition of a clock signal, and wherein said step of activating said first control signal comprises the step of activating said first control signal at least a second predetermined setup time before a second predetermined transition of said clock signal.

8. A method for synchronously accessing memory, comprising the steps of:

providing a first address for a first memory access at least a first predetermined setup time before a first transition of a clock signal;

activating a chip enable signal for said first memory access at least a second predetermined setup time before said first transition of said clock signal;

activating an output enable signal indicating a data phase of said first memory access a third predetermined setup time before a second transition of said clock signal subsequent to said first transition of said clock signal;

receiving a first data element accessed by said first address at a third transition of said clock signal subsequent to said second transition of said clock signal;

providing a second address for a second memory access at least said first predetermined setup time before said third transition of said clock signal; and

activating said first control signal indicating an address phase of said second memory access at least said second predetermined setup time before said third transition of said clock signal.

9. The method of claim 8 wherein said step of activating said output enable signal comprises the step of:

activating said output enable signal said third predetermined setup time before said second transition of said clock signal subsequent to said first transition of said clock signal by a predetermined number of wait states.

10. The method of claim 8 further comprising the steps of:

activating a burst data cycle in progress control signal a fourth predetermined setup time before a first plurality of transitions of said clock signal including said third transition of said clock signal; and

receiving a plurality of burst data elements during a second plurality of transitions of said clock signal subsequent to said third transition of said clock signal and corresponding to said first plurality of transitions of said clock signal.

11. A method for an integrated circuit microprocessor to synchronously access memory, comprising the steps of:

driving a first address for a first memory access during a first clock period;

activating a first control signal indicating a data phase of said first memory access during a second clock period subsequent to said first clock period by a predetermined number of wait states; and

receiving and latching a first data element accessed by said first address during a third clock period immediately subsequent to said second clock period;

driving a second address for a second memory access during said third clock period; and

activating said first control signal indicating an address phase of said second memory access during said third clock period.

12. The method of claim 11 wherein the step of activating said second control signal comprises the step of:

activating said second control signal during said second clock period subsequent to said first clock period by a predetermined number of wait states.

13. The method of claim 11 wherein said step of activating said first control signal comprises the step of activating a chip enable control signal.

14. The method of claim 11 wherein said step of activating said second control signal comprises the step of activating an output enable control signal.

15. The method of claim 11 further comprising the steps of:

activating a third control signal indicative of a burst data cycle in progress during said third clock period; and

receiving and latching a second data element during a fourth clock period subsequent to said third clock period.

16. The method of claim 11 further comprising the steps of:

activating a third control signal indicative of a burst data cycle in progress during a first plurality of clock periods including said third clock period; and

receiving and latching a plurality of burst data elements during a second plurality of clock periods subsequent to said third clock period and corresponding to said first plurality of clock periods.

17. The method of claim 11 wherein said step of driving said first address during said first clock period comprises the step of driving said first address at least a first predetermined setup time before first predetermined transition of a clock signal, and wherein said step of activating said first control signal comprises the step of activating said first control signal at least a second predetermined setup time before a second predetermined transition of said clock signal.