FPGA Intellectual Property
PCI Express*, Networking and Connectivity, Memory Interfaces, DSP IP, and Video IP
Announcements
Intel Support hours are Monday-Fridays, 8am-5pm PST, except Holidays. Thanks to our community members who provide support during our down time or before we get to your questions. We appreciate you!

Need Forum Guidance? Click here
Search our FPGA Knowledge Articles here.
5984 Discussions

Fixed-point multiplication, strange results

Altera_Forum
Honored Contributor II
758 Views

Hello everybody, 

 

I made DSPBuilder-to-Avalon-ST-Interface-Test which uses fixed-point multiplications (see attached picture for a oversimplified DSPBuilder-Model). 

 

However I get the following results, when trying to multiplicate the input with 1.5: 

0x00040000 ---> 0x00060000, correct: 4 * 1.5 = 6 

0x00030000 ---> 0x80040000, this isn't correct, is it? I expected 4.5 as result, in 2's complement fixed-point format it should look like this: 0x00048000 

 

It seems somehow rotated, but not exactly. What's going on? 

 

Regards, 

Sebastian
0 Kudos
0 Replies
Reply