Synthesis

[ghostrider_gr]

can you tell what this warning means?

Xst:3231 - The small RAM <Mram_ram_block> will be implemented on LUTs in order to maximize performance and save block RAM resources. If you want to force its implementation on block, use option/constraint ram_style.

 Is this because in my testbench I am using a few data, so there is no need for ram? What is LUT?

(actually is an info not a warning)

[austin]

g

LUT= look up table (do you ever use google?  Try it:  google LUT xilinx)

Your design has so few memories, that the synthesis tool is telling you that it will use DFF and look up table resources, instead, to save the BRAM for larger memory requirements.  If you do not need BRAM (you have plenty to spare) then follow the suggestion, and force the implementation using BRAM.

[eteam00]

Your testbench doesn't use memory, your synthesised design uses memory -- in module Mram_ram_block.

LUTs are the basic logic blocks of Xilinx FPGAs.  It is quite surprising that you haven't learned enough of the device you are using to have learned what a LUT is.  You simply cannot afford to design with FPGAs while avoiding some basic understanding of how they function.  I suggest you take the time to watch online video tutorials which can be found here.  One of these tutorials covers the subject of on-chip memory.

-- Bob Elkind

[ghostrider_gr]

---

eteam00 wrote:

Your testbench doesn't use memory, your synthesised design uses memory -- in module Mram_ram_block.

LUTs are the basic logic blocks of Xilinx FPGAs.  It is quite surprising that you haven't learned enough of the device you are using to have learned what a LUT is.  You simply cannot afford to design with FPGAs while avoiding some basic understanding of how they function.  I suggest you take the time to watch online video tutorials which can be found here.  One of these tutorials covers the subject of on-chip memory.

-- Bob Elkind

---

Thanks! can you give the link again, cause this one does not working.

[eteam00]

I have corrected the link in my original post.

-- Bob Elkind

[harikr]

XST does not implement small memories on block RAM. It does so to save block RAM resources. XST infers BRAM when Depth * Width is greater than 512 bits. If it is lesser than that, XST will infer a LUT RAM by default. If you would want your design to use BRAM's you can use -ram_style which will force the small RAM to be implemented using BRAM resources. The XST message explains this.

-Hari