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Old 10-11-2003, 09:00 PM
Joe Lawrence
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Default RAM in Xilinx Spartan II

I've got a beginner question concerning instantiating RAM inside a
Spartan II XC2S50 using WebPack. When attempting something like the
following:

type ram_array is array(0 to memsize-1) of std_logic_vector(width-1
downto 0);

the HDL synthesis reports using a 8-bit 1024-to-1 multiplexer. Is the
synthsizer trying to build the RAM out of flipflops? Should I build my
RAM out of ram32x1s type primitives instead?

-- Joe Lawrence
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Old 10-12-2003, 07:36 AM
Vinh Pham
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Default Re: RAM in Xilinx Spartan II

> type ram_array is array(0 to memsize-1) of std_logic_vector(width-1
> downto 0);


your type declaration looks okay, so it's probably a problem with the
"process" statement where you're using the signal of type "ram_array."
could you post that code up?

try searching for "inferring ram" in XST's user manual or on xilinx's web
site. they should give you a template of how to word your VHDL such that
XST can properly infer your ram.


--Vinh


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Old 10-14-2003, 06:23 PM
Joe Lawrence
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Default Re: RAM in Xilinx Spartan II

Vinh Pham wrote:
> try searching for "inferring ram" in XST's user manual or on xilinx's web
> site. they should give you a template of how to word your VHDL such that
> XST can properly infer your ram.


Thanks for the tip, I found a synthesis guide on the xilinx website that
provided me with the information I needed.


-- Joe Lawrence
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