Method and apparatus for generating a circular buffer address in integrated circuit that performs multiple communications tasks

• US 5,659,698 A
• Filed: 11/01/1994
• Issued: 08/19/1997
• Est. Priority Date: 11/01/1994
• Status: Expired due to Term

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Weng, Chia-Shiann, Curtis, Peter C.
• Primary Examiner(s): Treat, William M.
• Assistant Examiner(s): Winder, Patrice L.
• Application Number:
  US08/332,666
• Time in Patent Office: 1,022 Days
• Field of Search: 395/250, 395/872, 395/873, 395/874, 395/875, 395/876, 395/877, 395/800, 395/410, 395/421.07, 395/421.08, 395/421.1, 364/746
• US Class Current: 711/220
• CPC Class Codes: G06F 5/10 having a sequence of storage locations each being individually accessible for both enqueue and dequeue operations, e.g. using random access memory G06F5/065 takes precedence
• CPC Class Codes: G06F 9/3552 using wraparound, e.g. modulo or circular addressing

Abstract

A circular buffer address generation unit (630) may be accomplished by first determining a potential next address (635) based on a current address (644) and an address offset value (646). Having established the potential next address (635), the potential next address (635) is compared with an ending address (640) of the circular buffer. When the potential next address compared favorably with the ending address, use the potential next address as a new address (650), otherwise generate the new address (650) from a beginning address (642) of the circular buffer.

Claims

1. A method for generating an address for a circular buffer, the method comprising the steps of:

determining a potential next address based on a current address and an address offset value;

comparing the potential next address with an ending address for the circular buffer;

utilizing the potential next address as a new address when the potential next address compared in a first respect to the ending address;

utilizing a slide address based on the current address and a slide value as the new address when a slide command is received; and

utilizing a beginning address of the circular buffer as the new address when the potential next address compared in a second respect to the ending address.

2. The method of claim 1, wherein the step of determining the potential next address further comprises incrementing the current address by the address offset value.

3. The method of claim 1, wherein the step of determining the potential next address further comprises decrementing the current address by the address offset value.

4. The method of claim 1, wherein the step of comparing further comprises subtracting the potential new address from the ending address.

5. The method of claim 4, wherein the utilizing step further comprises determining that the comparison was favorable when the subtracting step produced a positive result.

6. The method of claim 4, wherein the utilizing step further comprises determining that the comparison was unfavorable when the subtracting step produced a negative result.

7. The method of claim 1, wherein the generating step further comprises generating the new address by:

subtracting the ending address from the potential next address to produce an overflow address; and

adding the overflow address to the beginning address.

8. The method of claim 1 further comprises generating the new address based on the current address and a slide value when a slide command is received.

9. A method for generating an address for a circular buffer, the method comprising the steps of:

comparing a current address with a limiting address, wherein the limiting address is an ending address of the circular buffer offset by an address offset value;

generating a new address by offsetting the current address with the address offset value when the current address compared in a first respect to the limiting address;

generating the new address based on the current address and a slide value when a slide command is received; and

generating the new address from a beginning address of the circular buffer when the current address compared in a second respect to the limiting address.

10. The method of claim 9, wherein the step of generating the new address by offsetting further comprises decrementing the current address by the address offset value.

11. The method of claim 9, wherein the step of generating the new address by offsetting further comprises decrementing th current address by the address offset value.

12. The method of claim 9, wherein the step of comparing further comprises subtracting the current address from the limiting address.

13. The method of claim 12, wherein the step of generating the new address by offsetting further comprises determining that the comparison was favorable when the subtracting step produced a positive result.

14. The method of claim 12, wherein the step of generating the new address from the beginning address further comprises determining that the comparison was unfavorable when the subtracting step produced a negative result.

15. An address generator for a circular buffer comprising:

memory that stores a current address, a beginning address of the circular buffer, an ending address of the circular buffer, and an address offset value;

an adder that adds the current address to the address offset value to produce a potential new address;

a comparator that compares the potential new address with the ending address and generates a first control signal when the potential new address compared in a first respect to the ending address and generates a second control signal when the potential new address compared in a second respect to the ending address; and

multiplexer that provides the potential new address as a new address when the first control signal is received and provides the beginning address as the new address when the second control signal is received and provides a slide address based on the current address and a slide value as the new address when a slide command is received.

16. The address generator of claim 15, wherein the address offset value comprises a negative value.

17. The address generator of claim 15 further comprises a wrap around generator operably coupled to the multiplexer, the memory, and the comparator, wherein the wrap around generator produces a wrap around address from the beginning address and an overflow address.

18. An address generator for a circular buffer comprising:

memory that stores a current address, a beginning address of the circular buffer, an address offset value and a limiting address of the circular buffer;

a comparator that compares the current address with the limiting address and generates a first control signal when the current address compared in a first respect to the limiting address and generates a second control signal when the current address compared in a second respect to the limiting address;

an adder that adds the current address to the address offset value to produce a potential new address.

a multiplexer that provides the potential new address as a new address when the first control signal is received and provides the beginning address as the new address when the second control signal is received; and

a second adder operably coupled to the multiplexer and the memory, wherein the second adder produces a slide address from the current address and a slide value.

19. The address generator of claim 18, wherein the limiting address comprises the address offset value subtracted from an ending address of the circular buffer.