Clock singals

[Mandilas Antony]

while synthesizing using XILINX ISE5, using verilog language, i got this
message

Clock Information:
------------------
-----------------------------------+------------------------+-------+
Clock Signal | Clock buffer(FF name) | Load |
-----------------------------------+------------------------+-------+
Mcompar__n0003_ALB1:O | NONE(*)(myValid_0_0) | 3 |
Mcompar__n0001_ALB:O | NONE(*)(mem_pos_7_0) | 11 |
temp:Q | NONE | 22 |
clk | BUFGP | 31 |
-----------------------------------+------------------------+-------+
(*) These 2 clock signal(s) are generated by combinatorial logic,
and XST is not able to identify which are the primary clock signals.
Please use the CLOCK_SIGNAL constraint to specify the clock signal(s)
generated by combinatorial logic.


I tried to use this constraint as i saw in the refernce, but nothing
changed..

i wrote these lines


// synthesis attribute clock_signal of myValid_0_0 is no;
// synthesis attribute clock_signal of mem_pos_7_0 is no;

but when i synthesize it again, nothing changed...

Best regards
Mandilas Antony

 

[Uwe Bonnes]

Mandilas Antony <mandilas_antony@yahoo.com> wrote:
: while synthesizing using XILINX ISE5, using verilog language, i got this
: message

: Clock Information:
: ------------------
: -----------------------------------+------------------------+-------+
: Clock Signal | Clock buffer(FF name) | Load |
: -----------------------------------+------------------------+-------+
: Mcompar__n0003_ALB1:O | NONE(*)(myValid_0_0) | 3 |
: Mcompar__n0001_ALB:O | NONE(*)(mem_pos_7_0) | 11 |
: temp:Q | NONE | 22 |
: clk | BUFGP | 31 |
: -----------------------------------+------------------------+-------+
: (*) These 2 clock signal(s) are generated by combinatorial logic,
: and XST is not able to identify which are the primary clock signals.
: Please use the CLOCK_SIGNAL constraint to specify the clock signal(s)
: generated by combinatorial logic.


: I tried to use this constraint as i saw in the refernce, but nothing
: changed..

: i wrote these lines


: // synthesis attribute clock_signal of myValid_0_0 is no;
: // synthesis attribute clock_signal of mem_pos_7_0 is no;

Do you have a net name myValid_0_0 in you design? I guess you have more
something like
wire [7:0] myValid[3:0];

So give the clock_signal attribute to the right net. Or better use CE and a
global clock.

Bye

--
Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
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