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Help me fix Xilinx warnings: outputs are unconnected in block

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david90

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My code was working but now i'm getting the warnings below after changing some values. I barely did anything. how do I fix this? all instances in my code are connected to each other.

WARNING:Xst:524 - All outputs of the instance <CLK1> of the block <clkdiv_1ms> are unconnected in block <fm>.
WARNING:Xst:1291 - FF/Latch <N1/q> is unconnected in block <fm>.
WARNING:Xst:524 - All outputs of the instance <C1> of the block <four_stage_BCD_counter> are unconnected in block <fm>.
WARNING:Xst:1291 - FF/Latch <DR1/q> is unconnected in block <fm>.
WARNING:Xst:1291 - FF/Latch <N2/out> is unconnected in block <fm>.
 

Re: xilinx warnings.

it seems that u r using schematic editor to connect ur blocks,
anyway, try fist to synthesize each block alone and check the warrnings associated with each.
 

Re: xilinx warnings.

Either the outputs are not connected, or the item it was connected to has been detected as redundant, and has been optimized away (yielding an unconnected output).
 

Re: xilinx warnings.

Code: 
module pwm(clk,in,pwm_out); 
input clk; 
input [7:0] in; 
output pwm_out; 

clkdiv N1(clk,gclk); 

reg i,pwm_out; 

always @(posedge gclk) 
begin 
for(i=0; i <=255; i=i+1) 
begin 
pwm_out<=1; 
end 

end 
endmodule

I get the "unconnected" warnings when I try to syn. the code above. It said that my block N1 output is unconnected but i'm using it in the always statement.
 

xilinx warnings.

Your "always" block doesn't do any useful work except set pwm_out to 1, so maybe everything got optimized away. If you are trying to generate a pulse 256 cycles long, you need some sort of counter, not a "for" loop.
 

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