Reputation: 694
How do I connect my different Verilog modules?
I'm making a reaction timer. I have made the individual modules before, and now all that remains is to use them collectively.
In other languages they are used as functions that return a value. Here I understand that modules are instantiated. I know how to instantiate as I have done for the LFSR, but for the LED multiplexer, I don't know how to.
Here is my LFSR code that will be instantiated into the main module:
module LFSR(
input clock,
input reset,
output [29:0] rnd
);
wire feedback = rnd[29] ^ rnd[5] ^ rnd[3] ^ rnd[0];
reg [29:0] random;
always @ (posedge clock or posedge reset)
begin
if (reset)
random <= 30'hF;
else
random <= {random[28:0], feedback};
end
assign rnd = random;
endmodule
And here is the main module. At places I have to call the LED circuit to display "Hi" and then later to display the stop watch. Ive marked them with comments.. How can i do that?
module reaction(
input clock,
input reset,
input start,
input stop,
output a,
output b,
output c,
output d,
output e,
output f,
output g,
output h,
output dp,
output led
);
reg [29:0] random;
LFSR random_gen(.clock(clock), .reset(reset), .rnd(random));
localparam [1:0]
idle = 2'b00,
start = 2'b01,
time_it = 2'b10,
stop = 2'b11;
reg state_reg, state_next;
reg [29:0] count_reg, count_next;
always @ (posedge clock or posedge reset)
begin
if(reset)
begin
state_reg <= idle;
count_reg <= 0;
end
else
state_reg <= state_next;
count_reg <= count_next;
end
always @ (*)
begin
state_next = state_reg; //default state stays the same
count_next = count_reg;
case(state_reg)
idle:
//"DISPLAY HI HERE .......... HOW??
if(start)
begin
count_next = random;
state_next = start;
end
start:
if(count_next == 750000000) // 750M equals a delay of 15 seconds.
begin
led = 1'b1;
state_next = time_it;
end
else
count_next = count_reg + 1;
time_it:
//START STOPWATCH????????
Now I have already made a working stopwatch. Its written below:
module stopwatch(
input clock,
input reset,
input start,
output a, b, c, d, e, f, g, dp,
output [3:0] an
);
reg [3:0] reg_d0, reg_d1, reg_d2, reg_d3; //registers that will hold the individual counts
reg [22:0] ticker; //23 bits needed to count up to 5M bits
wire click;
//the mod 5M clock to generate a tick ever 0.1 second
always @ (posedge clock or posedge reset)
begin
if(reset)
ticker <= 0;
else if(ticker == 5000000) //if it reaches the desired max value reset it
ticker <= 0;
else if(start) //only start if the input is set high
ticker <= ticker + 1;
end
assign click = ((ticker == 5000000)?1'b1:1'b0); //click to be assigned high every 0.1 second
always @ (posedge clock or posedge reset)
begin
if (reset)
begin
reg_d0 <= 0;
reg_d1 <= 0;
reg_d2 <= 0;
reg_d3 <= 0;
end
else if (click) //increment at every click
begin
if(reg_d0 == 9) //xxx9 - the 0.1 second digit
begin //if_1
reg_d0 <= 0;
if (reg_d1 == 9) //xx99
begin // if_2
reg_d1 <= 0;
if (reg_d2 == 5) //x599 - the two digit seconds digits
begin //if_3
reg_d2 <= 0;
if(reg_d3 == 9) //9599 - The minute digit
reg_d3 <= 0;
else
reg_d3 <= reg_d3 + 1;
end
else //else_3
reg_d2 <= reg_d2 + 1;
end
else //else_2
reg_d1 <= reg_d1 + 1;
end
else //else_1
reg_d0 <= reg_d0 + 1;
end
end
//The Circuit for Multiplexing - Look at my other post for details on this
localparam N = 18;
reg [N-1:0]count;
always @ (posedge clock or posedge reset)
begin
if (reset)
count <= 0;
else
count <= count + 1;
end
reg [6:0]sseg;
reg [3:0]an_temp;
reg reg_dp;
always @ (*)
begin
case(count[N-1:N-2])
2'b00 :
begin
sseg = reg_d0;
an_temp = 4'b1110;
reg_dp = 1'b1;
end
2'b01:
begin
sseg = reg_d1;
an_temp = 4'b1101;
reg_dp = 1'b0;
end
2'b10:
begin
sseg = reg_d2;
an_temp = 4'b1011;
reg_dp = 1'b1;
end
2'b11:
begin
sseg = reg_d3;
an_temp = 4'b0111;
reg_dp = 1'b0;
end
endcase
end
assign an = an_temp;
reg [6:0] sseg_temp;
always @ (*)
begin
case(sseg)
4'd0 : sseg_temp = 7'b1000000;
4'd1 : sseg_temp = 7'b1111001;
4'd2 : sseg_temp = 7'b0100100;
4'd3 : sseg_temp = 7'b0110000;
4'd4 : sseg_temp = 7'b0011001;
4'd5 : sseg_temp = 7'b0010010;
4'd6 : sseg_temp = 7'b0000010;
4'd7 : sseg_temp = 7'b1111000;
4'd8 : sseg_temp = 7'b0000000;
4'd9 : sseg_temp = 7'b0010000;
default : sseg_temp = 7'b0111111; //dash
endcase
end
assign {g, f, e, d, c, b, a} = sseg_temp;
assign dp = reg_dp;
endmodule
I hope I have been able to explain my problem.
Thank you for reading
Updated code:
module reaction(
input clock,
input reset,
input start,
input stop,
output a,
output b,
output c,
output d,
output e,
output f,
output g,
output dp,
output [3:0] an,
output reg led
);
wire [29:0] random;
reg go_hi, go_start;
//instantiate the random number generator
LFSR random_gen(.clock(clock), .reset(reset), .rnd(random));
//inistantiate module to display hi
say_hi sayhi(.clock(clock), .reset(reset), .go(go_hi), .a(a), .b(b), .c(c), .d(d),
.e(e), .f(f), .g(g), .dp(dp), .an(an));
//instantiate the millisecond timer
stopwatch timer(.clock(clock), .reset(reset), .start(go_start), .a(a), .b(b), .c(c), .d(d),
.e(e), .f(f), .g(g), .dp(dp), .an(an));
localparam [1:0]
idle = 2'b00,
starting = 2'b01,
time_it = 2'b10;
//stop = 2'b11;
reg state_reg, state_next;
reg [29:0] count_reg, count_next;
always @ (posedge clock or posedge reset)
begin
if(reset)
begin
state_reg <= idle;
count_reg <= 0;
end
else
state_reg <= state_next;
count_reg <= count_next;
end
always @ (*)
begin
state_next = state_reg; //default state stays the same
count_next = count_reg;
case(state_reg)
idle:
begin
//DISPLAY HI HERE
go_hi = 1;
if(start)
begin
go_hi = 0; //dont display hi anymore
count_next = random;
state_next = starting;
end
end
starting:
begin
if(count_next == 750) // 750M equals a delay of 15 seconds.
begin //and starting from 'rand' ensures a random delay
led = 1'b1;
state_next = time_it;
end
else
count_next = count_reg + 1;
end
time_it:
begin
go_start = 1;
if(stop)
go_start = 0;
end
endcase
end
endmodule
Upvotes: 3
Views: 10835
Answers (1)
Reputation: 35933
At places I have to call the LED circuit to display "Hi" and then later to display the stop watch. Ive marked them with comments.. How can i do that?
If you want to understand verilog you have to break the idea that you 'call' a module. Modules don't exist just when you want them to. In your case, you need to instantiate a stopwatch module, and connect the ports up (the line below the LFSR instantiation might be an appropriate place to do this).
When you do this, realize that your stopwatch is always driving the output LED, not just during certain states. If you want to change the display mode (to display a string like Hi, or to display the stopwatch time), you should have an input to your stopwatch module telling it what it should display.
Perhaps an input like display_mode could be used, where 2'd0 means display "hi", 2'd1 means display stopwatch time, 2'd2 means display dancing pattern, etc.
At appropriate points in your main reaction module, you could then change the value of display_mode, which will then change what stopwatch drives back out.
Upvotes: 3
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