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Question about accumulator word length in A8 core

Robert

Hi,

I have used some 32-bit microprocessor cores (non-ARM), which has a long word-length accumulator for some DSP operations, to avoid over-flow etc. After I check A8 core document, it is a surprise that I do not see any about this specification. It looks like it is a 32-bit as the register. For a FIR filter, 24-bit data/16-bit coefficients, at least 48-bit is needed for the accumulator. How to get satisfying results with A8 core?

Thanks,

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  • 0 in reply to Jacob Bramley

    Yes that's exactly right. As to coding you could consider a package from some supplier and they might have managed to optimize for the memory access as well. On the own coding side there's three levels of increasing speed and difficulty you might consider - C code using int for the operands and long long int for the 64 bit accumulator - this would use SMLAL, using C with the ARM 'NEON intrinsics' extensions, and straight assembler using NEON both of which would use VMLAL.

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  • 0 in reply to Jacob Bramley

    Yes that's exactly right. As to coding you could consider a package from some supplier and they might have managed to optimize for the memory access as well. On the own coding side there's three levels of increasing speed and difficulty you might consider - C code using int for the operands and long long int for the 64 bit accumulator - this would use SMLAL, using C with the ARM 'NEON intrinsics' extensions, and straight assembler using NEON both of which would use VMLAL.

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