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Altera_Forum's avatar
Altera_Forum
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14 years ago

Laboratory exercise 3: Part V [Verilog]

Hi there!

I am looking for some help or hints with Lab3 part V. I've done all the previous exercise, but I can't get any grip on that one.

I've written a module which is convert a for bit binary to one digit hex. But I don't know which previous circuit should I use? A gated D latch or a RS latch or something else?

Any help or a circuit schematic would be very helpfull.

Cheers!

5 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    could be a lot more helpful if you could post your laboratory question :)

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    --- Quote Start ---

    could be a lot more helpful if you could post your laboratory question :)

    --- Quote End ---

    That is obvious. Sorry. So here's the instructions from Lab3 Part V:

    --- Quote Start ---

    Part V

    We wish to display the hexadecimal value of a 16-bit number A on the four 7-segment displays, HEX7-4. We

    also wish to display the hex value of a 16-bit number B on the four 7-segment displays, HEX3-0. The values

    of A and B are inputs to the circuit which are provided by means of switches SW15-0. This is to be done by first

    setting the switches to the value of A and then setting the switches to the value of B; therefore, the value of A

    must be stored in the circuit.

    1. Create a new Quartus II project which will be used to implement the desired circuit on the Altera DE2-series

    board.

    2. Write a Verilog file that provides the necessary functionality. Use KEY0 as an active-low asynchronous

    reset, and use KEY1 as a clock input.

    3. Include the Verilog file in your project and compile the circuit.

    4. Assign the pins on the FPGA to connect to the switches and 7-segment displays, as indicated in the User

    Manual for the DE2-series board.

    5. Recompile the circuit and download it into the FPGA chip.

    6. Test the functionality of your design by toggling the switches and observing the output displays.

    --- Quote End ---

    This is the module that I mentioned above: 

    
module _7_seg(S, H);
	input  S;
	output  H;
	
	assign H = (~S&~S&~S&S) | (~S&S&~S&~S) | (S&~S&S&S) | (S&S&~S&S);
	assign H = (~S&S&~S&S) | (~S&S&S&~S) | (S&~S&S&S) | (S&S&~S&~S) | (S&S&S&~S) | (S&S&S&S);
	assign H = (~S&~S&S&~S) | (S&S&~S&~S) | (S&S&S&~S) | (S&S&S&S);
	assign H = (~S&~S&~S&S) | (~S&S&~S&~S) | (~S&S&S&S) | (S&~S&S&~S) | (S&S&S&S);
	assign H = (~S&~S&~S&S) | (~S&~S&S&S) | (~S&S&~S&~S) | (~S&S&~S&S) | (~S&S&S&S) | (S&~S&~S&S);
	assign H = (~S&~S&~S&S) | (~S&~S&S&~S) | (~S&~S&S&S) | (~S&S&S&S) | (S&S&~S&S);
	assign H = (~S&~S&~S&~S) | (~S&~S&~S&S) | (~S&S&S&S) | (S&S&~S&~S);
endmodule

    It converts a 4 bit binary into a single digit hexa, which can be displayed on the 7 seg display.

    I guess I should use 16 inscances of a gated d latch, somethig like this: 

    
module gated_D_latch(Clk, D, Q);
	input Clk, D;
	output Q;
	
	wire S, R, R_g, S_g, Qa, Qb /* synthesis keep */ ;
	
	assign S = D;
	assign R = ~D;
	
	assign S_g = ~(S & Clk);
	assign R_g = ~(Clk & R);
	assign Qa = ~(S_g & Qb);
	assign Qb = ~(Qa & R_g);
	
	assign Q = Qa;
endmodule

    All instances using the same Clk. But I don't know how should I wire this components up?
  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    if you have a 16 bit register as the input 

    
reg  input_data;
reg  a,b,c,d;
    you can access 4bit segments of it like 

    
a=input_data;
b=input_data;
c=input_data;
d=input_data;

    a register itself is a latch. what were you planning to achieve using the gated d latch?
  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    --- Quote Start ---

    what were you planning to achieve using the gated d latch?

    --- Quote End ---

    A circuit that can store a 16 binary number.

    Something like this:

    img132.imageshack.us/img132/7247/circx.png

    But instead of 4 instances I would use 16 so I could store 16 bits.

    ~CLR would be KEY0

    CLK would be ~KEY1 

    
module D_latch_async_rst(RST, CLK, DAT, Q);
	input RST, CLK, DAT;
	output reg Q;
	
	always @ (RST or CLK or DAT)
		if(~RST)
			Q = 1'b0;
                else if (CLK)
                        Q = DAT;
endmodule
  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    that should work.. i hope you realized that your circuit is level triggered and not edge triggered.. a 16 bit edge triggered d flip flop would look like this 

    
module D_latch_async_rst(RST, CLK, DAT, Q);     
     input RST, CLK;
     input  DAT;
     output reg  Q;
     always @ (posedge CLK) begin
             if(~RST)
                  Q = 1'b0;
             else 
                  Q = DAT;
     end
endmodule

    i hope someone will correct me if im wrong