Electrical computers and digital processing systems: memory – Storage accessing and control – Access timing
Reexamination Certificate
2000-03-31
2002-09-03
Kim, Matthew (Department: 2186)
Electrical computers and digital processing systems: memory
Storage accessing and control
Access timing
C711S131000, C711S149000, C711S150000, C711S170000
Reexamination Certificate
active
06446181
ABSTRACT:
BACKGROUND
This disclosure generally relates to digital signal processing and other processing applications, and specifically to a configurable, banked cache/SRAM memory architecture in such an application.
A digital signal processor (DSP) is a special purpose computer element that is designed to optimize performance for digital signal processing and other applications. The applications can include digital filters, image processing and speech recognition. The digital signal processing applications are often characterized by real-time operation, high interrupt rates and intensive numeric computations. In addition, the applications tend to be intensive in memory access operations, which may require the input and output of large quantities of data. Therefore, designs of digital signal processors may be quite different from those of general-purpose computers.
One approach that has been used in the architecture of digital signal processors to achieve high-speed numeric computation is the so-called “Harvard” architecture. This architecture utilizes separate, independent program and data memories so that the two memories may be accessed simultaneously. The digital signal processor architecture permits an instruction and an operand to be fetched from memory in a single clock cycle. A modified Harvard architecture utilizes the program memory for storing both instructions and operands to achieve full memory utilization. Thus, the program and data memories are often interconnected with the core processor by separate program and data buses.
When both instructions and operands (data) are stored in the program memory, conflicts may arise in the fetching of instructions. Certain instruction types may require data fetches from the program memory. In the pipelined architecture that may be used in a digital signal processor, the data fetch required by an instruction of this type may conflict with a subsequent instruction fetch. Such conflicts have been overcome in prior art digital signal processors by providing an instruction cache. Instructions that conflict with data fetches are stored in the instruction cache and are fetched from the instruction cache on subsequent occurrences of the instruction during program execution.
Although the modified Harvard architecture used in conjunction with an instruction cache provides excellent performance, the need exists for further enhancements to the performance of digital signal processors. In particular, increased computation rates and enhanced computation performance of the memory system provide advantages.
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Allen Michael
Anderson William C.
Booth, Jr. Lawrence A.
Kolagotla Ravi
Ramagopal Hebbalalu S.
Elmore Stephen
Fish & Richardson P.C.
Kim Matthew
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