I am trying to design a fsm for showing rotational which runs the 4-digit 7-segment LED display unit, to cause a rotating pattern of circulating squares in clockwise or counterclockwise. I am trying to fix the syntax errors in my case block but I am in verilog coding and I cannot find my mistake. Here is the code:
module fsm( EN, CW, clk, AN1,AN2,AN3,AN4, leds );
//inputs and outputs
input EN, CW, clk;
output AN1,AN2,AN3,AN4;
output reg leds[6:0];
//state register and parameters
reg state[3:0];
parameter s0 = 3'b000;
parameter s1 = 3'b001;
parameter s2 = 3'b010;
parameter s3 = 3'b011;
parameter s4 = 3'b100;
parameter s5 = 3'b101;
parameter s6 = 3'b110;
parameter s7 = 3'b111;
//states and outputs according to the states
always # (posedge clk)
begin
if (EN == 1)
begin
case(state)
s0: leds<=7'b1100011; if(CW)begin state <= s1; end else begin state <= s7; end
s1: leds<=7'b1100011; if(CW)begin state <= s2; end else begin state <= s0; end
s2: leds<=7'b1100011; if(CW)begin state <= s3; end else begin state <= s1; end
s3: leds<=7'b1100011; if(CW)begin state <= s4; end else begin state <= s2; end
s4: leds<=7'b1011100; if(CW)begin state <= s5; end else begin state <= s3; end
s5: leds<=7'b1011100; if(CW)begin state <= s6; end else begin state <= s4; end
s6: leds<=7'b1011100; if(CW)begin state <= s7; end else begin state <= s5; end
s7: leds<=7'b1011100; if(CW)begin state <= s0; end else begin state <= s6; end
endcase
end
end
//output logic
assign AN1 = ~((state == s0) | (state == s7));
assign AN2 = ~((state == s1) | (state == s6));
assign AN3 = ~((state == s2) | (state == s5));
assign AN4 = ~((state == s3) | (state == s4));
endmodule
A few things.
You should declare your vector signals like this:
output reg [6:0] leds;
//state register and parameters
reg [3:0] state;
And, you need to wrap each case item with a begin/end. I also spread the statements across a few lines, which might make it more readable:
s0: begin
leds <= 7'b1100011;
if (CW) begin
state <= s1;
end else begin
state <= s7;
end
end
Or, you could replace the if/else with a ternary:
s0: begin
leds <= 7'b1100011;
state <= (CW) ? s1 : s7;
end
Related
module FiniteStateMachine(output reg [2:0] Count, input clock, reset);
reg[2:0] state, next_state;
parameter S0 = 3'b000, S1 = 3'b001, S2 = 3'b010, S3 = 3'b011, S4 = 3'b100, S5 = 3'b101, S6 = 3'b110, S7 = 3'b111;
always # (posedge clock, negedge reset)
if(reset==0) state<=S0;
else state <= next_state;
always # (state)
case(state)
S0: begin
Count = S0;
next_state = S1;
end
S1: begin
Count = S1;
next_state = S2;
end
S2: begin
Count = S3;
next_state = S3;
end
S3: begin
Count = S7;
next_state = S4:
end
S4: begin
Count = S6;
next_state = S5;
end
S5: begin
Count = S4;
next_state = S0;
end
endcase
endmodule
Getting the error:
Syntax in assignment statement l-value
I've also tried "<=" instead of "=" for all the assignments in case, but I'm getting the same error.
You used a colon instead of a semicolon. Change:
next_state = S4:
to:
next_state = S4;
verilog error while I try to implement a traffic light system with six states I wanted to display lights red, green, yellow on the led display of ALTERA DE2 board
code is as below
module TrafficLight(clk, t, out);
input clk, t;
output out;
localparam s0=3'b000, s1=3'b001, s2=3'b010, s3=3'b011, s4=3'b100, s5=3'b101;
reg[2:0] state, next_state, t;
always#(posedge clk)
begin
state = next_state;
t = t - 1;
end
always#(t or state)
begin
case(state)
3'b000:
if(t < 5)
next_state = s0;
else
begin
next_state = s1;
assign out [5:0] = 6'b100001;
end
3'b001:
if(t < 1)
next_state = s1;
else
begin
next_state = s2;
assign out [5:0] = 6'b010001;
end
3'b010:
if(t < 1)
next_state = s2;
else
begin
next_state = s3;
assign out [5:0] = 6'b001001;
end
3'b011:
if(t < 5)
next_state = s3;
else
begin
next_state = s4;
assign out [5:0] = 6'b001100;
end
3'b100:
if(t < 1)
next_state = s4;
else
begin
next_state = s5;
assign out [5:0] = 6'b001010;
end
3'b101:
if(t < 1)
next_state = s0;
else
begin
next_state = s5;
assign out [5:0] = 6'b001001;
end
endcase
end
endmodule
What is wrong with this code can anyone fix it?
In Verilog an input cannot be a reg, as the error message says. Don't declare t as a reg by changing this line:
reg[2:0] state, next_state, t;
to this:
reg[2:0] state, next_state;
I having been trying to implement a simple sequence detector on a Nexys 3 (Spartan 6) board. The code works perfectly on Xilinx simulation but on the hardware, it doesn't work. Since I am new to FPGA implementation I couldn't solve this issue.
I dont know what changes I should make for the code to work in hardware.
It would be great if someone could help me..
And this is the code
module sequence( in, clock,reset,test);
input in;
input reset;
output reg test=0;
reg [3:0] state=0, next=0 ;
input clock;
always#( posedge clock)
begin
if(reset==1)
begin
state= 0;
end
else
begin
state=next;
end
end
always #*
begin
if(reset == 1)
begin
next=0;
test=0;
end
else
begin
case ( state )
'd0 : begin
if ( in==1)
begin
next=state+1;
end
else
next=next;
end
'd1 : begin
if ( in==1)
begin
next=state+1;
end
else
next=0;
end
'd2 : begin
if ( in==1)
begin
next=state+1;
end
else
next=0;
end
'd3 : begin
if ( in==1)
begin
next=state+1;
end
else
next=0;
end
'd4 : begin
if ( in==1)
begin
next=state+1;
test=1;
end
else
next=0;
end
default : begin
next=0;
test=0;
end
endcase
end
end
endmodule
I would change the beginning of your always block to:
always #*
begin
next = state;
test = 0;
case (state)
'd0 :
begin
if ( in==1)
next=state+1;
end
...
Setting a default assignment to all values in the state machine eliminates the possibility of creating an implicit latch. Your "next = next" statement shouldn't have any effect but might be creating latch (should probably be "next = state').
Also test is not assigned in every branch and has no default, so it will also create a latch.
The problems that I found in your Verilog code is given below.
Output variable test must be assigned in every case statement branches, else unwanted latches will form.
Use nonblocking assignments when you are specifying sequential circuit.
Try to code your sequence detector as below.
//sequence detector 101101
module fsm (rst,in1,clk,out1);
parameter s0 = 3'b000, s1 = 3'b001, s2 = 3'b010, s3 = 3'b011, s4 = 3'b100, s5 = 3'b101;
input rst,in1,clk;
output reg out1;
reg [2:0] state;
always #(posedge clk)
if (rst)
begin
state <= s0;
out1 <= 0 ;
end
else
case(state)
s0 : if (in1) begin state <= s1; out1 <= 0 ; end
else begin state <= s0; out1 <= 0 ; end
s1 : if (in1) begin state <= s0; out1 <= 0 ; end
else begin state <= s2; out1 <= 0 ; end
s2 : if (in1) begin state <= s3; out1 <= 0 ; end
else begin state <= s0; out1 <= 0 ; end
s3 : if (in1) begin state <= s4; out1 <= 0 ; end
else begin state <= s2; out1 <= 0 ; end
s4 : if (in1) begin state <= s1; out1 <= 0 ; end
else begin state <= s5; out1 <= 0 ; end
s5 : if (in1) begin state <= s1; out1 <= 1 ; end
else begin state <= s0; out1 <= 0 ; end
default: if (in1) begin state <= s0; out1 <= 0 ; end
else begin state <= s0; out1 <= 0 ; end
endcase
endmodule
The code below shows a finite state machine that controls a separate datapath module to find the GCD of two 4-bit numbers. I am currently getting the following errors, and I'm not sure why. Maybe they are due to some syntax I'm not aware of:
ERROR:HDLCompiler:806 - "D:/Xilinx Stuff/GCD123/Controller.v" Line 48: Syntax error near ";".
ERROR:HDLCompiler:806 - "D:/Xilinx Stuff/GCD123/Controller.v" Line 59: Syntax error near ";".
ERROR:HDLCompiler:806 - "D:/Xilinx Stuff/GCD123/Controller.v" Line 62: Syntax error near ";".
The code where the errors are encountered is below:
module Controller(start,reset,x_sel,y_sel,xlty,xgty,xequaly,clk);
input start,clk, reset, xlty, xgty,xequaly;
output x_sel,y_sel;
// Declare state register
reg [1:0]state;
// Declare states
parameter S0 = 0, S1 = 1, S2 = 2, S3 = 3, S4 = 4;
debounce startd(.clock(clk),.noisy(start),.clean(clean_start));
always # (posedge clk or posedge reset) begin
if (reset)
state <= S0;
else
case (state)
S0:
if (clean_start)
state <= S1;
else
state <= S0;
S1:
x_sel <= 0;
y_sel <= 0;
state <= S2;
S2:
if (xlty)
state <= S3;
else if(xgty)
state <= S4;
else if(xequaly)
state <= S5;
S3:
y_sel <= 1;
state <= S2;
S4:
x_sel <= 1;
state <= S2;
S5:
state <= S0;
endcase
end
endmodule
The lines that have the errors are y_sel <= 0; in the S1 state, state <= S2; in the S4 state and state <= S2; in the S3 state.
You need begin/end keywords around consecutive statements:
module Controller(start,reset,x_sel,y_sel,xlty,xgty,xequaly,clk);
input start,clk, reset, xlty, xgty,xequaly;
output x_sel,y_sel;
// Declare state register
reg [1:0]state;
// Declare states
parameter S0 = 0, S1 = 1, S2 = 2, S3 = 3, S4 = 4;
debounce startd(.clock(clk),.noisy(start),.clean(clean_start));
always # (posedge clk or posedge reset) begin
if (reset)
state <= S0;
else
case (state)
S0:
if (clean_start)
state <= S1;
else
state <= S0;
S1:
begin
x_sel <= 0;
y_sel <= 0;
state <= S2;
end
S2:
if (xlty)
state <= S3;
else if(xgty)
state <= S4;
else if(xequaly)
state <= S5;
S3:
begin
y_sel <= 1;
state <= S2;
end
S4:
begin
x_sel <= 1;
state <= S2;
end
S5:
state <= S0;
endcase
end
endmodule
I am trying to write Verilog HDL behavioral description of the machine specified in the state diagram below.
I am using if-else statements inside a case statement, and this gives me syntax errors regarding those lines. Do you see what the problem is?
My code is attached below:
module foo(y_out, state, x_in, clk, reset);
input x_in, clk, reset;
output reg y_out;
parameter s0 = 3'b000, s1 = 3'b001, s2 = 3'b010, s3 = 3'b011, s4 = 3'b100;
output reg[2:0] state;
reg[2:0] next_state;
always #(posedge clk) begin
if(reset == 1'b0) state <= s0;
else state <= next_state;
end
always #(state, x_in) begin
y_out = 0;
next_state = s0;
case(state, x_in)
s0:
if (!x_in) begin
next_state = s3;
y_out = 1'b0;
end
else begin
next_state = s4;
y_out =1'b1;
end
s1:
if (!x_in) begin
next_state = s1;
y_out = 1'b0;
end
else begin
next_state = s4;
y_out =1'b1;
end
s2: if (!x_in) begin
next_state = s2;
y_out = 1'b0;
end
else begin
next_state = s0;
y_out =1'b1;
end
s3: if (!x_in) begin
next_state = s1;
y_out = 1'b0;
end
else begin
next_state = s2;
y_out =1'b1;
end
s4: if (!x_in) begin
next_state = s2;
y_out = 1'b0;
end
else begin
next_state = s3;
y_out =1'b0;
end
default begin
next_state = s0;
y_out = 1'b0;
end
endcase
end
endmodule
module t_foo;
wire t_y_out, t_state;
reg t_x_in, t_clock, t_reset;
foo M1(t_y_out, t_state, t_x_in, t_clock, t_reset);
initial #200 $finish;
initial begin
t_reset = 0;
t_clock = 0;
#5 t_reset = 1;
repeat (16)
#5 t_clock = ~t_clock;
end
initial begin
t_x_in = 0;
#15 t_x_in = 1;
repeat (8)
#10 t_x_in = ~t_x_in;
end
initial begin
$monitor("ABC: %d, x_in: %d, Clock: %d, Reset: %d", state, t_x_in, t_clock, t_reset);
$dumpfile("5_41_wv.vcd");
$dumpvars;
end
endmodule
case statements expect a single item if this is to be based on multiple wire/regs then they need to be concatenated using {}.
I would avoid using things like always #(state, x_in) begin and just write always #* begin. The #* will take care of the sensitivity list.
Using the concatenation operator would allow you to remove the if statements:
always #* begin
y_out = 0;
next_state = s0;
case({state, x_in}) //Added {}
{s0, 1'b0}:
begin
next_state = s3;
y_out = 1'b0;
end
{s0, 1'b1}:
begin
next_state = s4;
y_out = 1'b1;
end
{s1, 1'b0}:
begin
next_state = s1;
y_out = 1'b0;
end
{s1, 1'b1}:
begin
next_state = s4;
y_out = 1'b1;
end
Using a casez would allow you to add do not cares to the next_state logic:
always #* begin
y_out = 0;
next_state = s0;
casez({state, x_in}) //Added {}
{s0, 1'bx}: //Do not care about the state of x_in
begin
next_state = s3;
y_out = 1'b0;
end
{s1, 1'b0}:
begin
next_state = s1;
y_out = 1'b0;
end
{s1, 1'b1}:
begin
next_state = s4;
y_out = 1'b1;
end
Change:
case(state, x_in)
to:
case(state)
That fixes a compile error for me. The case items in your code only depend on your state parameters, not x_in.
I also get a compile error in your testbench module. To fix it, change:
$monitor("ABC: %d, x_in: %d, Clock: %d, Reset: %d", state, t_x_in, t_clock, t_reset);
to:
$monitor("ABC: %d, x_in: %d, Clock: %d, Reset: %d", t_state, t_x_in, t_clock, t_reset);
And fix a warning by changing:
wire t_y_out, t_state;
to:
wire t_y_out;
wire [2:0] t_state;
Using state in case expression and xin in if condition is working fine. Please find below working code.
module fsm_state(
input clk,
input rst_n,
input xin,
output reg yout
);
reg [2:0] state;
reg [2:0] next_state;
parameter s0 = 3'b000,
s1 = 3'b001,
s2 = 3'b010,
s3 = 3'b011,
s4 = 3'b100;
always # (posedge clk) begin
if (!rst_n)
state = s0;
else
state = next_state;
end
always #*
begin
yout = 1'b0;
case (state)
s0: begin
if (xin) begin
yout = 1'b1;
next_state = s4;
end
else
next_state = s3;
end
s1: begin
if (xin) begin
yout = 1'b1;
next_state = s4;
end
else
next_state = s1;
end
s2: begin
if (xin) begin
yout = 1'b1;
next_state = s0;
end
else
next_state = s2;
end
s3: begin
if (xin) begin
yout = 1'b1;
next_state = s2;
end
else
next_state = s1;
end
s4: begin
if (xin)
next_state = s3;
else
next_state = s2;
end
endcase
end
endmodule
Thanks