Abstract: In one embodiment, a pipelined processor is described that includes an execution pipeline having a plurality of stages and a multi-cycle instruction (MCI) controller adapted to assert a stall signal to stall the multi-cycle instruction within one of the stages of the execution pipeline. The MCI controller is adapted to issue a plurality of instructions to subsequent stages in the pipeline while the multi-cycle instruction is stalled.

Abstract: In one embodiment, a state machine receives a plurality of instructions from an instruction register to be processed by a digital signal processor. After receiving a single RTI, the state machine loads each of the plurality of instructions one at time and determines the validity of each instruction. If the instruction is valid, the state machine transfers the instruction to the decoder. If the instruction is invalid or if a no-operation instruction is present, the state machine discards the instruction and immediately loads the next instruction.

Abstract: In one embodiment, a digital signal processor includes look ahead logic to decrease the number of bubbles inserted in the processing pipeline. The processor receives data containing instructions in a plurality of buffers and decodes the size of a first instruction. The beginning of a second instruction is determined based on the size of the first instruction. The size of the second instruction is decoded and the processor determines whether loading the second instruction will deplete one of the plurality of buffers.

Abstract: A programmable processor is adapted to detect exception conditions associated with one or more instructions before the instructions are executed. The detected exception conditions may be stored with the one or more instructions in a prefetch unit. Then, the exception conditions may be issued in parallel with the issuance of the instructions.

Abstract: In one embodiment, an integrated circuit provides a test access port that communicates with scan chain registers in a processor core. The integrated circuit synchronizes data transferred between a debug controller that operates under control of a test clock (TCK) and the processor core that operates under control of a processor clock (CLK).

Abstract: In one embodiment, a trace buffer circuit for use with a pipelined digital signal processor (DSP) may include a series of interconnected registers that operate as a first-in first-out (FIFO) register on a write operation and a last-in first-out (LIFO) register on a read operation. On the write operation, a branch target/source address pair may be written to a first pair of trace buffer registers and, the contents of each register may be shifted two registers downstream. On the read operation, one instruction address may be read from a top register, and the contents of each register may be shifted one register upstream. The trace buffer may also include structure to enable compression of hardware and software loops in the program flow. A valid bit may be assigned to each instruction address in the trace buffer and a valid bit buffer with a structure parallel to that of the trace buffer may be provided to track the valid bits.

Abstract: A system includes a first processor, a second processor and a circuit. The first processor includes a first terminal and enters a first test mode in response to the first terminal having a first signal state. The second processor includes a second terminal. The second processor enters a second test mode in response to the second terminal having a second signal state. The circuit may regulate the timing of the first and second signal states to place both the first processor in the first test mode and the second processor in the second test mode at approximately the same time. The circuit may regulate the timing of the signals to cause the first and second processors to resume normal modes of operation at approximately the same time.

Abstract: In one embodiment, a digital signal processor includes look ahead logic to decrease the number of bubbles inserted in the processing pipeline. The processor receives data containing instructions in a plurality of buffers and decodes the size of a first instruction. The beginning of a second instruction is determined based on the size of the first instruction. The size of the second instruction is decoded and the processor determines whether loading the second instruction will deplete one of the plurality of buffers.

Abstract: In one particular embodiment, a processor receives and processes a plurality of instruction from a single instruction register. The processor loads the plurality of instructions into a single register and determines the number and size of instructions while the instructions are in the register. Each of the plurality of instructions is then simultaneously presented to the decoder. The decoder then decodes a first of the plurality of instructions and determines whether any additional instructions are present.

Abstract: In one embodiment, a programmable processor is adapted to support hardware loops. The processor may include hardware such as a first set of registers, a second set of registers, a first pipeline, and a second pipeline. Furthermore, the processor may include a control unit adapted to efficiently implement the hardware when performing a hardware loop.

Abstract: A processor may support a self-nesting mode in which an interrupt may preempt another interrupt of the same priority level. The execution of an interrupt service routine (ISR) for an interrupt may be deferred until the ISR for a subsequently received interrupt of the same priority level is completed.

Abstract: In an embodiment, a pipelined digital signal processor (DSP) may generate a valid bit in an alignment stage. The valid bit may be qualified in a decode stage in response to receiving a stall signal and/or a kill signal. The valid bit output from the decode stage may be stored in a latch in an address calculation (AC) stage. The valid bit may be held in the latch by a latch enable circuit in response to receiving a stall signal. The valid bit output from the latch may be qualified in the AC stage. The circuit in the AC stage including the latch, the latch enable circuit, and a valid bit qualifier may be repeated in downstream pipeline stages, for example, the execution stages.

Abstract: A programmable processor that includes a pipeline with a number of stages. A stall controller is associated with the pipeline, and detects a hazard condition in at least one of those stages. The stall controller produces a set of signals that can control the stages individually, to stall stages of the pipeline in order to avoid a hazard. In an embodiment, a bubble is formed in the pipeline which allows one instruction to complete prior to allowing the pipeline to continue.

Abstract: In one embodiment, techniques are disclosed for causing a programmable processor to process one instruction at a time. Single-step debugging may be performed by taking an exception after each instruction or by invoking emulation mode after each instruction. The particular single-step debugging technique may be based upon state of control bits, or may be based upon the processor's current mode of operation, or both.

Abstract: In one embodiment, a processor receives coded instructions and converts the instructions to a second code prior to execution. The processor may be a digital signal processor. A decoder in the processor determines the destination of the instructions and performs decoding functions based on the destination.

Abstract: In one embodiment, a programmable processor searches an array of N data elements in response to N/M machine instructions, where the processor has a pipeline configured to process M data elements in parallel. In response to the machine instructions, a control unit directs the pipeline to retrieve M data elements from the array of elements in a single fetch cycle, concurrently compare the data elements to M current extreme values, and update the current extreme values, as well as M references to the current extreme values, based on the comparisons.

Abstract: A programmable processor is adapted to detect exception conditions associated with one or more instructions before the instructions are executed. The detected exception conditions may be stored with the one or more instructions in a prefetch unit. Then, the exception conditions may be issued in parallel with the issuance of the instructions.

Abstract: Register adjustment is performed based on adjustment values determined at multiple stages within a pipeline of a processor. In one embodiment, a programmable processor is adapted to include a speculative count register. The speculative count register may be loaded with data associated with an instruction before the instruction commits. However, if the instruction is terminated before it commits, the speculative count register may be adjusted. A set of counters may monitor the difference between the speculative count register and its architectural counterpart.