Texas Instruments Corporation

Texas Instruments France

Vincent Gillet

Gilbert Laurenti

Herve Catan

Karim Djafarian

Douglas E Deao

Mark L Buser

Shigeshi Abiko

Marc Couvrat

Jean-Pierre Giacalone

Eric L Badi

Armelle Laine

Gael Clave

Alain Boyadjian

Anne Lombardot

Jean-Marc Philippe Bachot

Francois Theodorou

Yves Masse

Eric Ponsot

Jack Rosenzweig

Jean-Louis Tardieux

Walter A Jackson

Laurent Ichard

Emmanuel Ego

Frederic Nidegger

David Russell

N M Ganesh

A processor is provided that is a programmable digital signal processor (DSP) with variable instruction length, offering both high code density and easy programming. Architecture and instruction set are optimized for low power consumption and high efficiency execution of DSP algorithms, such as for wireless telephones, as well as pure control tasks. A coefficient data pointer is provided for accessing coefficient data for use in a multiply-accumulate (MAC) unit. Monitoring circuitry determines when the coefficient data pointer is modified (step ). When an instruction is executed (step ) that requires a coefficient datum from memory in accordance with the coefficient data pointer, a memory access is inhibited (step ) if the coefficient data pointer has not been modified since the last time a memory fetch was made in accordance with the coefficient data pointer and the previously fetched coefficient datum is reused. However, if the coefficient data pointer was modified since the last time a memory fetch was made in accordance with the coefficient data pointer, then the required coefficient datum is fetched from memory (step ). A shadow register within the MAC unit execution pipeline temporarily saves coefficient data for possible reuse.

Processor with pointer tracking to eliminate redundant memory fetches

A processing engine for executing instructions in parallel comprises an instruction buffer for holding at least two instructions, with the first instruction in a first position and the second instruction in a second position. A first decoder provides decoding of the first instruction and generates first control signals. The first control signals include first resource control signals, first address generation control signals, and a first validity signal indicative of the validity of the first instruction in the first position. A second decoder provides decoding of the second instruction and generates second control signals. The second control signals include second resource control signals, second address generation control signals, and a second validity signal indicative of the validity of the second instruction in the second position. Arbitration and merge logic is provided for arbitrating between the first and second control signals and for merging the first and second control signals for controlling power of execution of the instructions in accordance with a set of parallelism rules. A conditional execution unit is responsive to false condition signals from the arbitration and merge logic to inhibit or modify the effect of the control signals. The parallelism rules provide for efficient instruction execution, and the avoidance of resource conflicts.

Preventing the execution of a set of instructions in parallel based on an indication that the instructions were erroneously pre-coded for parallel execution

A processing engine includes an instruction buffer operable to buffer single and compound instructions pending execution. A decode mechanism is configured to decode instructions from the instruction buffer. The decode mechanism is arranged to respond to a predetermined tag in a tag field of an instruction, which predetermined tag is representative of the instruction being a compound instruction formed from separate programmed memory instructions. The decode mechanism is operable in response to the predetermined tag to decode at least first data flow control for a first programmed instruction and second data flow control for a second programmed instruction. The use of compound instructions enables effective use of the bandwidth available within the processing engine. A soft dual memory instruction can be compiled from separate first and second programmed memory instructions. A compound address field of the predetermined compound instruction can be arranged at the same bit positions as the address field for a hard compound memory instruction, that is a compound instruction which is programmed. In this case the decoding of the addresses can be started before the operation code of the instructions have been decoded. To reduce the number of bits in the compound instruction, addressing can be restricted to indirect addressing and the operation codes for at least the first instruction can be reduced in size. In this way, the compound instruction can be arranged to have the same number of bits in total as the sum of the bits of the separate programmed instructions.

Dual access instruction and compound memory access instruction with compatible address fields

A processor ( ) is provided that is a programmable fixed point digital signal processor (DSP) with variable instruction length, offering both high code density and easy programming. Architecture and instruction set are optimized for low power consumption and high efficiency execution of DSP algorithms, such as for wireless telephones, as well as pure control tasks. The processor includes an instruction buffer unit ( ), a program flow control unit ( ), an address/data flow unit ( ), a data computation unit ( ), and multiple interconnecting busses. Dual multiply-accumulate blocks improve processing performance. A memory interface unit ( ) provides parallel access to data and instruction memories. The instruction buffer is operable to buffer single and compound instructions pending execution thereof. A decode mechanism is configured to decode instructions from the instruction buffer. The use of compound instructions enables effective use of the bandwidth available within the processor. A soft dual memory instruction can be compiled from separate first and second programmed memory instructions. Instructions can be conditionally executed or repeatedly executed. Bit field processing and various addressing modes, such as circular buffer addressing, further support execution of DSP algorithms. The processor includes a multistage execution pipeline with pipeline protection features. Various functional modules can be separately powered down to conserve power. The processor includes emulation and code debugging facilities with support for cache analysis.

Microprocessors

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Le Rouret, France

Vincent Gillet