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zlan01
Beginner
178 Views

do the LPM_SHIFTREG must be used in the spi serial receiving code when the clock fequency is too fast?

input       spi_data_i;

output reg   spi_data_o;

 

reg [15:0]shift_sender;

reg [15:0]shift_receiver;

 

code 1: spi receiving code=========================================================

always @(posedge spi_clk_50M or negedge spi_rst_n)

begin      

   if(~spi_rst_n)

         shift_receiver   <= 16'h0;

   else       

           shift_receiver   <= {shift_receiver[14:0],spi_data_i};      

end

 

 

code2 :spi sending code ============================================================

 

always @(posedge spi_clk_50M or negedge spi_rst_n)

begin      

   if(~spi_rst_n)

      begin

         shift_sender   <= 16'h0;

         spi_data_o         <= 1'b0;

      end

   else

      begin

         spi_data_o <= shift_sender[15];

         shift_sender  <= {shift_sender[14:0],1'b0}; 

      end

end

============================

I am implemented a spi interface which clock is 50Mhz shown above, the sending code work correctly,but the receiving code can not receive any data using verilog to implement the shifting in register?

I have implemented a uart interface which clock fequency is 1Mhz using the simliar code above,the receiver and sender all work correctly;

do the LPM_SHIFTREG must be used in the serical receiving code when the clock fequency is too fast such as 50Mhz?why ?

 

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2 Replies
51 Views

Hi,

 

May I know which device you are using? It is mentioned that the receiving code cannot receive any data using Verilog to implement the shifting in register? Could you explain in details and provide error message (if any). Do you check the simulation result and sdc constraints?

 

Thanks.

51 Views

Hi,

 

May I know if you have any updates?

 

Thanks.

Reply