Hello, We are thinking about switching from 8051 to Cortex M3. At the moment everything is written in assembler. Now I simply would like to know, how many assembler statements a Cortex M3 CPU will take to evaluate a square root from a 48 Bit integer value. Is this (square root of a 48 Bit integer) included in a math library and a nobrainer or is only floating point supported. I am new and just evaluating, what the switch means for us, so I would highly appreciate to get an answer to this question.
Thanks a lot.
Uwe Renschler
Nice to hear that a fixed point sqrt is trivial. I hope that it is also trivial to get the answer to my question: How many assembler statements are executed from a Cortex M3 CPU to figure out the square root of a 48 Bit integer value ? (min, max values if variable) What I read so far, is that the library could be used. And that is really trivial. But I don t know, what the library looks like and the 48 Bit square root is in our application performance critical. (At the moment we have implemented it using a 128 Entry lookup table and it takes between 40 and 60 8051 assembler statements). The same like in the brackets before would I like to know, for the Cortex M3 with the standard math lib.
I never worked with a 8051, however I can assure you that the M3 is lighting fast compared to it. I am confident that you'd be delighted with the calculation speed.
I meant: "lightening fast", of course.
I hope that it is also trivial to get the answer to my question: How many assembler statements are executed from a Cortex M3 CPU to figure out the square root of a 48 Bit integer value ?
That depends mostly on what algorithm you intend to use.
This one here is quite interesting:
www.embedded.com/.../9802fe2.htm
However, I don't believe you're going to beat the speed of a table-lookup-plus-interpolation solution, if the slight imprecision of such a solution is acceptable in your application.
The square root calculation will require a number of shifts and additions for each step, and each step will process two input bits, so you'll end up with 24 times a whole bunch of shifts, additions, and one conditional. That may still be faster than 60 statements on an 8051 (especially if it's a 12-clocker), but if you use a lookup-table-based approximation on the ARM, it'll be even faster than the exact calculation.
No; I think you really meant, "lightning fast"...?
;-)
:-)