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Valued Contributor III
1,333 Views

Verilog coding

Hi all, 

 

I am just start to learn Verilog and immediately had a problem - please take a look at code - why "repeat (10) does not working? 

I was expected a 5 pulse train at every oop pulse - but in simulation the is no changes of pls output at all. 

I tried to use for and while condition - same result - no pulse train. 

 

/////////////////////////////////////////////////////////////////////////////////////////////////// 

 

module buff_gen (oop,pls); 

input oop; 

wire oop;  

 

output pls;  

reg pls; 

 

initial begin pls = 0; end 

 

 

always @ (posedge oop)  

begin 

 

repeat (10)  

begin  

# 5 pls = ~pls; 

end 

 

end 

 

endmodule 

 

//////////////////////////////////////// 

 

please tell me what I am doing wrong. 

 

thanks 

cicga
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Valued Contributor III
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did you input a rising edge on oop? 

And what are you simulating? RTL or netlist? repeat is not a synthesisable construct and is for simulation only.
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Valued Contributor III
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If you're trying to simulate this, you need to have an input stimulus for oop to make it work at all. Otherwise, pls will just stay low. And as Tricky mentioned, the repeat construct is not synthesizable if you're trying to make this work in hardware.

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Valued Contributor III
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Thanks for help, 

 

1. Where I can find specs for Verilog used in Quartus 2 and its specs - what can be used for simulation only etc. 

 

2. Yes I am sending oop signal ,but a problem is that not only repeat() don't work but nether for() and while(): 

 

 

 

module buff_gen (oop,pls); 

 

input oop; 

wire oop;  

 

output pls;  

reg pls; 

integer i;  

 

initial begin pls = 0; end 

 

always @ (posedge oop) begin 

 

for (i=0;i<10;i=i+1)  

begin  

pls = ~pls; 

end 

 

end 

 

endmodule 

 

please check attachment with waveform pictures.
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Valued Contributor III
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1. Try the HDL coding styles from the quartus handbook: https://people.ece.cornell.edu/land/courses/ece5760/de1_soc/hdl_style_qts_qii51007.pdf 

 

2. That is the quartus simulator. It only supports netlist simulation which will require synthesis. If you check the warnings, you'll probably find some code has been ignored. Also note that# N statements are also ignored for syntheis. 

Loops can only be used for parallel circuits. Not for events that occur in time. You need to build the circuit for that purpose, probably with a counter.
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