Altera ALTERA_MULT_ADD Saturation

Status
Not open for further replies.
S

shaiko

Advanced Member level 5
Joined
Aug 20, 2011
Messages
2,644
Helped
303
Reputation
608
Reaction score
297
Trophy points
1,363
Activity points
18,302
Hello,

Has anyone ever configured the ALTERA_MULT_ADD core to use Saturation and Rounding ?
 

Saturation is a DSP hardware feature of some FPGA families, e.g. Stratix II - IV. It can be only used in mult_add IP if the hardware supports it.
 
Reactions: shaiko

    S

    shaiko

    Points: 2
    Helpful Answer Positive Rating
Saturation is a DSP hardware feature of some FPGA families, e.g. Stratix II - IV. It can be only used in mult_add IP if the hardware supports it.
Click to expand...
So if I'm using Arria V for example - I'll have to do it with logic ?
 

Yes. ieee.fixed_pkg saturation and rounding features can be e.g. used.
 
Reactions: shaiko

    S

    shaiko

    Points: 2
    Helpful Answer Positive Rating
is ieee.fixed_pkg well supported for synthesis ?
 

shaiko said:
is ieee.fixed_pkg well supported for synthesis ?
Click to expand...

Depends on tool, version, etc.
I think only synopsys supports the 2008 version. Other tool support the '93 compatible version (that you will need your own copy of).

Otherwise rounding and saturation is a simple operation.
Round = +0.5 and chop the LSBs off.
Saturate is just some compares and a mux.
 
Reactions: shaiko

    S

    shaiko

    Points: 2
    Helpful Answer Positive Rating
Otherwise rounding and saturation is a simple operation.
Round = +0.5 and chop the LSBs off.
Saturate is just some compares and a mux.
Click to expand...
Simple as it is - it'll almost certainly be slower than the speed of the hardened DSP silicon.
A weak link in the chain.

The more I look at it the more it seems like Xilinx's DSP48 is richer than Altera's block (at least for Arria & Cyclone devices).
 

Otherwise rounding and saturation is a simple operation.
Round = +0.5 and chop the LSBs off.
Saturate is just some compares and a mux.
Click to expand...
Yes, you can write functions to perform the operations. The convenience of fixed_pkg is that is is redefining the arithmetic operators. Altera Quartus has ieee.fixed_pkg supported with VHDL 2008 since version 15.
 
Reactions: shaiko

    S

    shaiko

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…