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dmitryl_home
Adventurer
Adventurer
315 Views
Registered: ‎11-08-2017

Why there are no memories with slall sizes?

Hi All,

Why there are no memories (BRAMs) with small sizes (e.g. 32*8)? Why it's not worth manufacturing them?

Thank you

 

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drjohnsmith
Teacher
Teacher
313 Views
Registered: ‎07-09-2009

This sounds like a home work question,

Look at the resources in the chip you have.

There are thousands of small RAM, 16 or 32 bits by 1,

      all of which your code can use 

They only become inefficient if you need bigger amounts of ram,

    which is where the Block Ram come in

      and if they are not big enough, some FPGs have SLA ram blocks of megga bits,

 

BTW:

   If this is home work,

     most universities etc monitor the forums to see who is taking short cuts,

   

 

 

 

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dmitryl_home
Adventurer
Adventurer
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Registered: ‎11-08-2017

I've looked into the Spartan-7 Memory Resources User Guide (see the link below), and did not find there small memories as you mentioned (32x1 etc memories).

https://www.xilinx.com/support/documentation/user_guides/ug473_7Series_Memory_Resources.pdf

So, where the small memories, which you mentioned, are described? Are you about the distributed memories? But they are LUT-based...

What's the SLA RAM Blocks? Where can I read about them? Does Spartan have such memories?

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drjohnsmith
Teacher
Teacher
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Registered: ‎07-09-2009

spartan 7 does not have SLA blocks, so you wont find them in the spartan 7 data sheet

   look into the larger ultrascale + devices,

 

You are right about the small memories, we tend to forget about them, they have been around so long,

  We tend to think of "memory" as the built in larger blocks of dedicated memory , as in Block Rams, 

The smaller rams, are the Look Up Table ( LUT ) configuration registers,

   this gives an idea as to the registers, in this case used as a shift register,

https://www.xilinx.com/support/documentation/application_notes/xapp465.pdf

 

and this one on how to use them as RAM

https://www.xilinx.com/support/documentation/application_notes/xapp464.pdf

 

 

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dmitryl_home
Adventurer
Adventurer
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Registered: ‎11-08-2017

cannot find the SLA blocks description in the Ultrascale+ docs. Could you please send a link to the descriptions?

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drjohnsmith
Teacher
Teacher
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Registered: ‎07-09-2009

The XCVU31P has the HBM memories,

which is may be what you mean by the SLA ?

 

You seem to be covering a big range of parts here, 

    which sort of implies that you are not loking at making a design,

   On premise other shave also asked similar recently 

      can I ask, is this a home work / study question ?

If so , you do realise that universities do monitor these sites also,

 

 

 

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