Full Precision option in Fixed-Point Converter MATLAB
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In the HDL Coder and Fixed-Point Converter tool in MATLAB there is an option to set the precision as LSB (least-significant bit), MSB (Most-significant bit) and FullPrecision. What does FullPrecision actually refer too? How precise is full precision? What does it do?
Walter Roberson le 28 Fév 2022
How the product data type is determined, specified as one of these values:
'FullPrecision' – The full precision of the result is kept.
'KeepLSB' – Keep the least significant bits. Specify the product word length. The fraction length is set to maintain the least significant bits of the product.
'KeepMSB' – Keep the most significant bits. Specify the product word length. The fraction length is set to maintain the most significant bits of the product.
'SpecifyPrecision' – Specify the word and fraction lengths or slope and bias of the product.
So if you were multiplying a 11 bit value by an 11 bit value by a 53 bit value, then the first part (11 x 11) could need as much as 22 bits to get exact output; then 53 bits more would take you up to 75 bits to get the exact output.
Full precision means full precision: number of bits of output is the sum of the number of bits of the inputs. No rounding, no truncation.
It is like doing long multiplication by hand: every digit of the inputs contributes to the length of the results.
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