On May 25, 7:47=A0pm, "shantesh"
<shantesh84@n_o_s_p_a_m.n_o_s_p_a_m.gmail.com> wrote:
> Hello,
>
> I'm curious to know if there is a way we could tell the synthesizer to us=
e
> registered mode of BRAM when using ram_style "block" attribute.
>
> The registered mode otherwise can be enabled by instantiating a BRAM with
> DOA_REG, DOB_REG set to 1 and REGCEA, REGCEB set to '1'.
>
> For example, the VHDLcode below infers a BRAM. However, it does not enabl=
e
> the registered mode. To get around with it, I've added a process which
> registers the output wherever this memory is instantiated. This added
> register occupies a slice. Is there a way I can tell the synthesizer to u=
se
> the register inside of BRAM (that way I could save resources).
>
> =3D=3D=3D=3D
> =A0 attribute ram_style =A0 =A0 =A0 =A0: string;
> =A0 attribute ram_style of RAM : signal is "block";
>
> begin
>
> =A0 process (clk)
> =A0 begin
> =A0 =A0 if clk'event and clk =3D '1' then
> =A0 =A0 =A0 if en =3D '1' then
> =A0 =A0 =A0 =A0 if we =3D '1' then
> =A0 =A0 =A0 =A0 =A0 RAM(conv_integer(addr)) <=3D di;
> =A0 =A0 =A0 =A0 end if;
> =A0 =A0 =A0 =A0 do =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0<=3D RA=
Rather than adding a process, have you tried simply adding a register
stage in the process where the RAM is inferred? Somethimes
synthesizers understand your intentions better when they're all
together.
Reply by shantesh●May 25, 20102010-05-25
Hello,
I'm curious to know if there is a way we could tell the synthesizer to use
registered mode of BRAM when using ram_style "block" attribute.
The registered mode otherwise can be enabled by instantiating a BRAM with
DOA_REG, DOB_REG set to 1 and REGCEA, REGCEB set to '1'.
For example, the VHDLcode below infers a BRAM. However, it does not enable
the registered mode. To get around with it, I've added a process which
registers the output wherever this memory is instantiated. This added
register occupies a slice. Is there a way I can tell the synthesizer to use
the register inside of BRAM (that way I could save resources).
====
attribute ram_style : string;
attribute ram_style of RAM : signal is "block";
begin
process (clk)
begin
if clk'event and clk = '1' then
if en = '1' then
if we = '1' then
RAM(conv_integer(addr)) <= di;
end if;
do <= RAM(conv_integer(addr));
end if;
end if;
end process;
end;
=====
Thanks,
Shantesh
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