Hardware function generator support in a DSP

Abstract

The present invention relates to digital signal processors with an integrated module configured to compute a Coordinate Rotation Digital Computer (CORDIC) in a pipeline. The pipelined module can advantageously complete computation of one CORDIC computation for each clock pulse applied to the CORDIC module, thereby providing a CORDIC computation for each clock pulse. One embodiment advantageously computes a first portion of a computation with a lookup table and a second portion in accordance with a CORDIC algorithm. Advantageously, data in a CORDIC pipeline is automatically advanced in response to read instructions and can be automatically advanced from the beginning of the pipeline to the end of the pipeline to reinitialize the pipeline. This allows information to be retrieved from the CORDIC pipeline with relatively little overhead The automatic starting and stopping of the CORDIC pipeline advantageously allows the retrieval of computations from efficient pipeline architectures on an as-needed basis.

Description

RELATED APPLICATION [0001] This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60 / 231,280, filed Sep. 8, 2000, the entirety of which is hereby incorporated by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention generally relates to digital signal processing. In particular, the present invention relates to a Coordinate Rotation Digital Computer (CORDIC) in a digital signal processor (DSP). [0004] 2. Description of the Related Art [0005] A Coordinate Rotation Digital Computer (CORDIC) algorithm performs vector coordinate rotations by using simple iterative shifts and add / subtract operations, which are relatively easy to implement in hardware. Advantages of the CORDIC algorithm have been well documented by U.S. Pat. No. 4,896,287 to O'Donnell, et al., U.S. Pat. No. 4,937,775 to Engeler, et al., and U.S. Pat. No. 5,684,435 to Bergen, the entireties of which are hereby incorporated by reference. [...

AI Technical Summary

Benefits of technology

[0010] Embodiments of the invention quickly and efficiently process the CORDIC algorithm in a pipeline. Advantageously, data in the CORDIC pipeline is automatically advanced in response to read instructions and can be automatically advanced from the beginning of the pipeline to the end of the pipeline to reinitialize the pipeline. This allows a controller or a digital signal processor (DSP) to efficiently retrieve information from the CORDIC pipeline with relatively little overhead. The automatic starting and stopping of the CORDIC pipeline advantageously allows the retrieval of computations from efficient pipeline architectures on an as-needed basis and advantageously avoids having to store relatively large amounts of computations from a pipeline in memory.

[0011] One embodiment of the present invention includes a design of a modified CORDIC Function Generator that can be used in a DSP core. The modified CORDIC Function Generator is pipelined to provide a new output on every clock edge. A relatively small initial latency allows the modified CORDIC Function Generator time to process new data through the pipeline.

[0012] In one embodiment, an architecture for an Execution Block, which can be implemented in the DSP core, advantageously uses the CORDIC Function Generator to reduce both chip area and DSP idle cycles. An example of a Radix-2 butterfly illustrates how this CORDIC Function Generator improves the implementation of such DSP algorithms.

Problems solved by technology

Disadvantageously, the amount of data that is stored in a ROM lookup table can quickly surpass practical size and cost limitations.

By contrast, where a ROM lookup table is relatively small and inexpensive, the number of available functions and the resolution of the data available are limited.

Disadvantageously, typical software implementations of function generation are relatively slow.

Typical software routines use iterative techniques, and take relatively time consuming multiple cycles to generate a trigonometric function.

Where a conventional CORDIC is pipelined, execution can be faster, but conventional pipelined CORDICs have relatively little integration with other hardware.

Disadvantageously, other hardware, such as microprocessors and DSPs, closely monitor or control conventional pipelined CORDICs or store the results of the conventional pipelined CORDIC in relatively large and expensive memory devices.

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