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Anonymous
Not applicable
12,204 Views

DCM

I've generated a DCM with the clocking wizard, set to increase 50Mhz signal to 75Mhz

 

I've initiated it in my top module

 

this is from my topmodule:

 

gen_75mhz: clockmanagerexample
                    port map(   CLKIN_IN => clk_50mhz,
                                    RST_IN => '0',
                                    CLKFX_OUT => clk_75mhz,
                                    CLKFX180_OUT => clk_75mhz_180,
                                    CLKIN_IBUFG_OUT => open,
                                    LOCKED_OUT => open );

 

this is from my DCM:

entity clockmanagerexample is
   port ( CLKIN_IN        : in    std_logic;
          RST_IN          : in    std_logic;
          CLKDV_OUT       : out   std_logic;
          CLKFX_OUT       : out   std_logic;
          CLKFX180_OUT    : out   std_logic;
          CLKIN_IBUFG_OUT : out   std_logic;
          CLK0_OUT        : out   std_logic);
end clockmanagerexample;

 

When I did a simulation with modelsim, my clk_75mhz is 0 all the way,while my clk_50mhz is changing, though not at 50Mhz...

 

how can I get my 75mHz signal out?

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7 Replies
ajmirg
Xilinx Employee
Xilinx Employee
12,185 Views
Registered: ‎05-14-2008

Normally LOCKED signal should go high when DCM is working.

 

Which version of ISE are you using?

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sbroderick
Visitor
Visitor
12,177 Views
Registered: ‎06-26-2008

As I recall, the DCM needs to be held in reset for several clock cycles. I recall a similar problem. I would recommand reviewing the datasheet because I think I found my solution there.
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Anonymous
Not applicable
12,147 Views

it worked with modelsim...but when i try to translate it, it tells me this

 

ERROR:NgdBuild:753 - "top.ucf" Line 4: Could not find instance(s) 'DCM_SP_INST'
   in the design.  To suppress this error specify the correct instance name or
   remove the constraint.

 

my top.vhd, make use of a component from clockmanager.vhd ...inside clockmanager.vhd has

 


   DCM_SP_INST : DCM_SP
   generic map( CLK_FEEDBACK => "1X",
            CLKDV_DIVIDE => 2.0,
            CLKFX_DIVIDE => 1,
            CLKFX_MULTIPLY => 2,
            CLKIN_DIVIDE_BY_2 => FALSE,
            CLKIN_PERIOD => 20.000,
            CLKOUT_PHASE_SHIFT => "NONE",
            DESKEW_ADJUST => "SYSTEM_SYNCHRONOUS",
            DFS_FREQUENCY_MODE => "LOW",
            DLL_FREQUENCY_MODE => "LOW",
            DUTY_CYCLE_CORRECTION => TRUE,
            FACTORY_JF => x"C080",
            PHASE_SHIFT => 0,
            STARTUP_WAIT => FALSE)

 

under its architecture

 

what's wrong huh?

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golson
Scholar
Scholar
12,110 Views
Registered: ‎04-07-2008

I took a look at what you have written seems correct to me.  Are you targeting Spartan 3?  I suspect you need to if you want to use this DCM.

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kaztani
Visitor
Visitor
12,096 Views
Registered: ‎06-12-2008

Hi,

What number are you using for the time resolution of ModelSim?   I found that the DCM model did not work properly with large time resolution for high frequency. 

Try 1psec for the time resolution if you use 1nsec.

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Anonymous
Not applicable
12,093 Views

I solved the problem by using "Inst_xxxetc/DCM_SP_INST" to locate the instance
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jalpa_29
Participant
Participant
9,864 Views
Registered: ‎10-17-2008

can u tell me  why you have written"Inst_xxxetc/" is it specific to ur design?

 

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