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Re: [f-cpu] New snapshot for EU_INC and EU_CMP



Hello,

I have read your code and, unfortunately, I have found an 
unsynthesisable structure :

   tree_find_lsb : entity find_lsb
                               ^^^^^
the entity keyword is not supported at this position.

See IEEE P1076.6-2001 for more information on VHDL RTL synthesis subset.

Just an Illusion

PS : If some one need a version of the IEEE P1076.6-2001 standard, I can 
upload a version on seul.org.

Etienne LABARRE wrote:

>Hi all,
>
>New snapshot include a lot of changes and features :
>
>INC unit and CMP unit are now two different units, for simplify and
>decrease latency
>
>Both units are based to the same component : find_lsb
> It's a binary tree for find the first null lsb in a word.
> It supports SIMD operations (size of chunk = 8, 16, 32, 64, 128, 256
> bits)
> It's based to only one function : and_reduce. It's is a standard
> function of ieee.std_logic_1164 library.
> Latency of find_lsb is not exactly know, but i can estimate this
> to 3 level of 4-and, and 1 level of mux, or more exactly 2 level of
> 8-and, and 1 level of mux. The precise latency is not important,
> because max latency will be fixed by timing constraints during synthetisis process.
> (It's an explain of my choice of standard function. "Just an
> Illusion"
> will can explain this more easy that me, i think...)
>
>For INC unit, the data flow is :
> 1 level of mux
> find_lsb : 3 level of 4-and, 1 level of mux
> 1 level of xor
> 2 level of mux
> total is 8 levels.
> Critical datapath is only for ABS operation.
>
> Supported operations :
> INC, DEC, NEG, ABS, LSB0, LSB1
>
> All operations are tested by my testbenches.
>
>For CMP unit, the data flow is :
> 1 level of xor,
> 1 level of mux,
> find_lsb : 3 level of 4-and, 1 level of mux
> 2 level of mux,
> total is 8 levels.
> Critical datapath is for CMP, MIN, MAX, SORT operations.
>
> Supported operations :
> CMP, MIN, MAX, SORT, MSB0, MSB1
>
> Today, only CMP, MSB0 and MSB1 are tested by my testbenches. Todo :
> test for others operations.
>
>
>All operations can need only one cycle, if we accept the 8 level of gates
>latency.
>
>Etienne.
>

-- 
______________________________
"The matrix is my world, I am a shadow.
Shadow in world, shadow in life. Don't try to keep me,
I am a Corpo's Killer.
Don't follow me or die..."
		The KingWalker - 1996



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