Hi all, Firstly sorry for the English post here, though I'm a student in Germany but my German is really limited, by which I cant express myself. However I know this is a hot forum, and I am wondering if someone can help me a bit. I am using mega128 to do an embedded control application, in a step I need to do a 32bit/32bit division. This is a bit tough for me because I am using assembly language and mega128 doesnt have division instruction. I searched a lot on the internet but still being confusion. Could anyone show me a sample code or a division algorithm on how to do it? Really appreciate that. Tudou
oh, that's really fast, thanks a lot!
some years ago, I had a similar problem. At this time, I wrote some subroutines for multiply and divide, by only in 16bit. But I think, it will help you increase it to 32bit. The underlaying idea is the same, like you calculate this on papier, like in the first years of school: example: nbr#1 nbr#2 0100'1010 : 0001'0010 shift nbr#2 one cycle LESS than nbr#1<nbr2: 0100'1010 (nbr#1) 0100#1000 (nbr#2*) subract: ---------------------- ..... shift right...
thanks, but 32bit/32bit algorithm is only available when the dividend is bigger than the divisor, right? what if my dividend is smaller than divisor, I tried, and everytime I got 0. Any idea?
Of course it is, Integer-Divison is (almost) always rounded downwards - and the next whole number smaller than 1 is 0 -- there are no ints between them ;) You could use some kind of fix-point arithmetics, where the LSB represents i.e. 1/256 (or 0.001, or ...) rather than 1. But in that case you have to take care that your program can cope with that (put the "." in outputs and things alike) or you google for a Floating-point Library ( but that sounds like an assembler-nightmare to me). sry, my (written) english is a little rusty ;) hth. Jörg
here are "DIRTY DAN"s MATH TRICKS", also called "RetroDan": http://8515.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=50912&view=next about division on AVR
thank you so much for the information