I'm new to fpgas in general. I want to make counter that iterates each time SCK sees a rising edge. The issue i'm having with my code is that it seems to count twice. Two leds are lit each time there is a rising edge transition - as opposed to just one led. Any idea where this may be coming from?
module spi_slave(pcEn, LED, clk, SCK);
input clk, SCK;
output reg pcEn;
output reg [7:0] LED = 8'h00;
reg r1 = 0;
reg r2 = 0;
reg r3 = 0;
reg [3:0] cnt = 4'b0000;
always #(posedge clk)
begin
r1 <= SCK;
r2 <= r1;
pcEn <= r1 && !r3;
if (pcEn == 1) begin
cnt = cnt + 4'b0001;
if (cnt == 4'b0001) begin
LED[0] = 1'b1;
end
else if (cnt == 4'b0010) begin
LED[1] = 1'b1;
end
else if (cnt == 4'b0011) begin
LED[2] = 1'b1;
end
else if (cnt == 4'b0100) begin
LED[3] = 1'b1;
end
else if (cnt == 4'b0101) begin
LED[4] = 1'b1;
end
else if (cnt == 4'b0110) begin
LED[5] = 1'b1;
end
else if (cnt == 4'b0111) begin
LED[6] = 1'b1;
end
else if (cnt == 4'b1000) begin
LED[7] = 1'b1;
end
else
LED = 8'h00;
end
else
#100;
r3 <= r2;
end
endmodule
The counter is counting twice because you are comparing r1 & !r3.
r1->r2->r3 .it takes 2 clocks for r3 to be set after r1 equal 1. This implies that r1&!r3 condition will remain valid for 2 clocks. The pcEn will be generated for 2 clocks , Hence the counter will count twice.
r1 && !r2 or if you want a delay r2 && !r3 should work fine.
you should be able to see this behavior in a waveform to debug.Use $dumpvars; in your simulation to view the waveform.
Also there are couple of change to improve the code.
use of reset.
consistently use non-blocking assignment .
there is no need for #100 delay.
module spi_slave(pcEn, LED, clk, SCK,rst_n);
input clk, SCK,rst_n;
output reg pcEn;
output reg [7:0] LED ;
reg r1 ;
reg r2 ;
reg r3 ;
reg [3:0] cnt ;
always #(posedge clk or negedge rst_n)
begin
if ( rst_n == 0 )
begin
r1 <=0 ;
r2 <= 0 ;
r3 <= 0 ;
cnt <= 0 ;
LED <=0 ;
pcEn <=0 ;
end
else
begin
r1 <= SCK;
r2 <= r1;
r3 <= r2;
pcEn <= r2 && !r3;
if (pcEn == 1) begin
cnt <= cnt + 4'b0001;
if (cnt == 4'b0001) begin
LED[0] <= 1'b1;
end
else if (cnt == 4'b0010) begin
LED[1] <= 1'b1;
end
else if (cnt == 4'b0011) begin
LED[2] <= 1'b1;
end
else if (cnt == 4'b0100) begin
LED[3] <= 1'b1;
end
else if (cnt == 4'b0101) begin
LED[4] <= 1'b1;
end
else if (cnt == 4'b0110) begin
LED[5] <= 1'b1;
end
else if (cnt == 4'b0111) begin
LED[6] <= 1'b1;
end
else if (cnt == 4'b1000) begin
LED[7] <= 1'b1;
end
else
LED <= 8'h00;
end
end
end
endmodule
First of # delays are not synthesizable, they are delays for simulation only.
Generally is considered best practice to separate block and non-blocking logic into different always blocks. always #* for combinational (blocking assignments), and always #(posedge clk) for sequential (non-blocking assignments). FYI : Verilog supports case-statements which make coding value compare easier then nesting else-if.
I thing you may want to use r2 && !r3 instead of r1 && !r3 as Rahul also pointed out
always #* begin
if (pcEn == 1'b0) begin
next_cnt = cnt;
next_LED = LED;
else begin
next_cnt = cnt + 4'b0001;
next_LED = 8'h00; // Rest all to 0s
if(cnt >= 8'h8) next_cnt = 4'b0000; // optional : assuming you want to roll back before waiting another 8 SCK toggles
case(cnt)
4'b0000 : next_LED[0] = 1'b1;
4'b0001 : next_LED[1] = 1'b1;
// ...
4'b0111 : next_LED[7] = 1'b1;
endcase
end
end
always #(posedge clk) begin
r1 <= SCK;
r2 <= r1;
r3 <= r2;
pcEn <= r2 && !r3;
cnt <= next_cnt;
LED <= next_LED;
end
Related
For a lab I must create the logic to use on a Digilent PMOD ALS. In the lab requirenment I cannot use the sclk signal on the sensitivity list and therefore use a state machine to create the 2.5 MHz clk signal to send to the PMOD ALS. See the code below:
module sens_interface(
input clk, //clk 10Mhz
input reset_n,
input [15:0] delay,
input datain,
output reg sclk,
output reg cs_n,
output reg [3:0] Cout,
output reg [3:0] Dout,
output reg [5:0] cnt
);
//params
//state machine 1
parameter SA0 = 3'b000;
parameter SA1 = 3'b001;
parameter SA2 = 3'b010;
parameter SA3 = 3'b011;
parameter SD0 = 3'b100;
parameter SD1 = 3'b101;
//state machine 2
parameter SR0 = 2'b00;
parameter SR1 = 2'b01;
parameter SR2 = 2'b10;
parameter SR3 = 2'b11;
//pmod als registers
//reg sclk; //2.5Mhz clk
//reg cs_n; //
reg [14:0] data_reg;
//count registers
//reg [5:0] cnt;
reg [15:0] cnt_d;
reg [5:0] cnt_r;
//state registers
reg [2:0] state_sclk;
reg [1:0] state_data;
//State Machine 1
always # (posedge clk)begin
if(reset_n == 1'b0)begin
cs_n <= 1'b1;
sclk <= 0;
cnt <= 6'd0;
cnt_d <= 16'd0;
end
else
case(state_sclk)
SA0:begin
sclk <= 1'b1;
state_sclk <= SA1;
if (cnt <= 6'd17)
cs_n <= 1'b0;
else
cs_n <= 1'b1;
end
SA1:begin
state_sclk <= SA2;
end
SA2:begin
sclk <= 1'b0;
cnt <= cnt + 1;
state_sclk <= SA3;
end
SA3:begin
if(cnt == 6'd21)begin
cnt <= 0;
state_sclk <= SD0;
end
else
state_sclk <= SA0;
end
SD0:begin
cnt_d <= delay;
state_sclk <= SD1;
end
SD1:begin
if (cnt_d == 0)
state_sclk <= SA0;
else
cnt_d <= cnt_d - 1;
end
default:begin
state_sclk <= SA0;
end
endcase
end
always # (posedge clk)begin
if (reset_n == 1'b0)begin
cnt_r <= 0;
data_reg <= 0;
end
else begin
case (state_data)
SR0:begin
if (cs_n == 1'b1 && sclk == 1'b1)
state_data <= SR1;
end
SR1: begin
if (cs_n == 1'b1)begin
state_data <= SR0;
cnt_r <= 0;
end
else if (sclk == 1'b0)
state_data <= SR2;
end
SR2:begin
if (cs_n == 1'b1)begin
state_data <= SR0;
cnt_r <= 0;
end
else if (cnt_r == 15)
state_data <= SR3;
else if (sclk == 1'b1)begin
data_reg [14-cnt_r] <= datain;
cnt_r <= cnt_r + 1;
state_data <= SR1;
end
end
SR3:begin
if (cs_n == 1) begin
Cout <= data_reg [11:8];
Dout <= data_reg [7:4];
state_data <= SR0;
end
end
default:begin
state_data <= SR0;
end
endcase
end
end
endmodule
I tried to make a simulation of it and the simulation indicates that after my cnt register reaches 15 it just cuts out and goes to 0.
simulation
That behavior is caused by your SA3 state.
SA3:begin
if(cnt == 6'd21)begin
cnt <= 0;
state_sclk <= SD0;
end
else
state_sclk <= SA0;
end
end
When your cnt == 6'd21 (which is 6'h15) the cnt is set to zero.
The generic variable names and lack of comments makes it difficult to see why this is not the expected behavior.
I have created a counter that counts up to 30. I have an output signal out. At two particular counts, i.e., when counter reaches 10 (first) and when counter reaches 15 (second), I want the output to become low. Somehow I'm missing a basic logic here as only at one particular count (either at 10 or 15) I'm able to make the output zero.
Here is the code
module user_def_pulse(
output integer counter,
output reg out,
input clk, reset
);
parameter no_of_counts = 30;
parameter first = 10;
parameter second = 15;
initial
begin
counter = 0;
out = 1'b0;
end
always #(posedge clk)
begin
if (reset)
begin
counter <= 1'b0;
end
else if (counter == no_of_counts)
begin
counter <= 1'b0;
out <= 1'b0;
end
else
begin
if ((counter == first) || (counter == second))
out <= 1'b0;
else
begin
counter <= counter + 1;
out <= 1'b1;
$display($time," The value of counter is %d", counter);
end
end
end
endmodule
Here is the test bench
module user_def_pulse_tb(
);
parameter time_period = 10;
wire [31:0] COUNTER;
wire OUT;
reg CLK, RESET;
user_def_pulse udp1 (.counter(COUNTER), .out(OUT), .clk(CLK), .reset(RESET));
initial
begin
CLK = 1'b0;
RESET = 1'b1;
#20 RESET = 1'b0;
end
always
#time_period CLK = ~CLK;
endmodule
Here is the output waveform.
The problem with your code is that is stops incrementing the counter as soon as it hits the first value. You need to keep incrementing the counter. I moved the increment outside of the if ((counter == first) || ... clause.
always #(posedge clk) begin
if (reset) begin
counter <= 1'b0;
end else if (counter == no_of_counts) begin
counter <= 1'b0;
out <= 1'b0;
end else begin
counter <= counter + 1;
$display($time," The value of counter is %d", counter);
if ((counter == first) || (counter == second)) begin
out <= 1'b0;
end else begin
out <= 1'b1;
end
end
end
I have written following code which produces pulse of different width.I want the code to produce a single pulse according to select line.
If select line is
00 pulse width = 1 us ,
01 pulse width = 10 us
. .
11 pulse width = 1000 us
The input clock is of 10 Mhz.
But according to code I am getting continuous pulse if I don't provide any other value of selection line.How can I achieve only one pulse?
module pulse(input wire [1:0] sel , //selection lines s1 s0
input clk,
input rst_n,
output reg flag, //for checking conditions
output reg [13:0] Q, // output of 14 bit counter
output reg pulse, //output pulse
output reg count); //also for checking conditions
wire flag_d , count_d;
assign flag_d = ( (sel == 2'b00 | sel == 2'b01 | sel == 2'b10 | sel == 2'b11) && count == 1'b0)? 1'b1 : flag;
assign count_d = ( (sel == 2'b00 | sel == 2'b01 | sel == 2'b10 | sel == 2'b11) && count == 1'b0)? 1'b1 : count;
always #(posedge clk , negedge rst_n)
begin
if(!rst_n)
begin
Q <= 14'h0;
count <= 1'b0;
pulse <= 1'b0;
flag <= 1'b0;
end
else
begin
flag <= flag_d;
count <= count_d;
if(flag)
begin
case(sel)
2'b00: Q <= 14'd11;//count from 11 to 1
2'b01: Q <= 14'd101;//count from 101 to 1
2'b10: Q <= 14'd1001;//count from 1001 to 1
2'b11: Q <= 14'd10001;//count from 10001 to 1
default: Q <= 14'd0;
endcase
flag <= 1'b0;
end
else
begin
if(Q != 14'h1 && Q != 14'h0)
begin
Q <= Q - 14'h1;
pulse <= 1'b1;
end
else
begin
pulse <= 1'b0;
count <= 1'b0;
end
end
end
end
endmodule
Is this code in a good coding style considering the synthesis and hardware of the circuit? if not than what changes I should apply?..
I couldn't figure out the point of flag_d and count_d. Also ( (sel == 2'b00 | sel == 2'b01 | sel == 2'b10 | sel == 2'b11) && count == 1'b0) simplifies to (count == 1'b0). sel should not be Xs or Zs.
I think you want something more like the following:
reg [13:0] next_Q;
always #* begin
if (Q==0) begin
case(sel)
2'b00 : next_Q = 14'd10;
2'b01 : next_Q = 14'd100;
2'b10 : next_Q = 14'd1000;
2'b11 : next_Q = 14'd10000;
endcase
end
else begin
next_Q = Q - 1;
end
end
always #(posedge clk, negedge rst_n) begin
if (!rst_n) begin
pulse <= 1'b0;
Q <= 14'd0;
end
else begin
// if (Q==0) pulse <= !pulse; // high and low pulse will have equal if sel is constant
pulse <= (Q!=0); // or high pulse based on sel, low is one clk
Q <= next_Q;
end
end
working example: http://www.edaplayground.com/x/GRv
module pulse(input wire [1:0] sel, // No need for the sel to be wire
input clk,
input rst_n,
output reg [13:0] Q,
output reg pulse,
input input_stb, // Input is valid
input output_ack,
output output_stb,
output input_ack); // 2 Flag model
reg s_input_ack ;
reg s_output_stb;
parameter get_inputs = 4'd0,
counter = 4'd1;
always #(posedge clk , negedge rst_n)
begin
case (state)
get_inputs:
s_input_ack <= 1;
if (s_input_ack && input_a_stb)
begin
s_input_ack <= 0;
case(sel)
00: Q <= 14'd11;//00000000001010;
01: Q <= 14'd101;//00000001100100;
10: Q <= 14'd1001;//00001111101000;
11: Q <= 14'd10001;//10011100010000;
default: Q <= 14'd0;
endcase
state <= counter;
end
counter:
begin
s_output_stb <= 1;
if (s_output_stb && output_z_ack)
begin
s_output_stb <= 0;
if(Q != 14'h1 && Q != 14'h0)
begin
Q <= Q - 1'b1;
pulse <= 1'b1;
end
else
begin
pulse <= 1'b0;
end
end
state <= get_inputs;
end
endcase
if(!rst_n)
begin
Q <= 14'h0;
pulse <= 1'b0;
s_input_ack <= 0;
s_output_stb <= 0;
end
assign input_ack = s_input_ack;
assign output_stb = s_output_stb;
end
endmodule
*Still needs work , add registers and necessary signals accordingly. Will edit at a later point in time
`timescale 1ns / 1ps
module stopwatch(
input clock,
input reset,
input increment,
input start,
output [6:0] seg,
output 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;
wire click;
//the mod 1kHz clock to generate a tick ever 0.001 second
always # (posedge (clock) or posedge (reset))
begin
if(reset)
begin
ticker <= 0;
end
else
begin
if (start)
begin
if(ticker == (100000 - 1)) //if it reaches the desired max value reset it
ticker <= 0;
else if (increment)
ticker <= ticker;
else
ticker <= ticker + 1;
end
end
end
//increment a second everytime rising edge of down button
reg [3:0] inc_temp;
always # (posedge (increment))
begin
if (reg_d3 == 9)
inc_temp = 0;
else
inc_temp = reg_d3 + 1;
end
assign click = ((ticker == (100000 - 1))?1'b1:1'b0); //click to be assigned high every 0.001 second
//update data start from here
always # (posedge (clock) or posedge (reset))
begin
if(reset)
begin
reg_d0 <= 0;
reg_d1 <= 0;
reg_d2 <= 0;
reg_d3 <= 0;
end
else
begin
if (increment)
begin
reg_d3 <= inc_temp;
reg_d0 <= reg_d0;
reg_d1 <= reg_d1;
reg_d2 <= reg_d2;
end
else if (click) //increment at every click
begin
if(reg_d0 == 9) //xxx9 - 1th milisecond
begin
reg_d0 <= 0;
if (reg_d1 == 9) //xx99 - 10th milisecond
begin
reg_d1 <= 0;
if (reg_d2 == 9) //x999 - 100th milisecond
begin
reg_d2 <= 0;
if(reg_d3 == 9) //9999 - The second digit
reg_d3 <= 0;
else
reg_d3 <= reg_d3 + 1;
end
else
reg_d2 <= reg_d2 + 1;
end
else
reg_d1 <= reg_d1 + 1;
end
else
reg_d0 <= reg_d0 + 1;
end
else
begin
reg_d3 <= reg_d3;
reg_d0 <= reg_d0;
reg_d1 <= reg_d1;
reg_d2 <= reg_d2;
end
end
end
//Mux for display 4 7segs LEDs
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;
//update the data to display to LEDs
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 seg = sseg_temp;
assign dp = reg_dp;
endmodule
I'm trying to design a stop watch, but I'm stuck at the increment thing. The intent is when I press increment(a button), the reg_d3 will increment by one and hold its state until the button is released. I'm able to make the clock stop when the button is pressed, but I can't update the reg_d3. I always receive
[Place 30-574] Poor placement for routing between an IO pin and BUFG
I don't know why; I use increment in the clkdivider just find.
I think the problem is related to this part of your code:
always # (posedge (increment))
begin
if (reg_d3 == 9)
inc_temp = 0;
else
inc_temp = reg_d3 + 1;
end
You are basically using an input signal as a clock, and that is completely discouraged when designing for a FPGA. The P&R tries to re-route an IO pin to a BUFG (global buffer) inside the FPGA so it can be used as a clock.
For FPGA design, you should use one clock signal for all your always #(posedge...) constructions, and use input signals to conditionally load/update the register.
To do that, you have first to synchronize your increment signal to your clk, so avoiding metastability issues:
reg incr1=1'b0, incr2=1'b0;
always #(posedge clk) begin
incr1 <= increment;
incr2 <= incr1;
end
wire increment_synched = incr2;
Then, deglitch increment_synched and detect a rising edge in it:
reg [15:0] incrhistory = 16'h0000;
reg incr_detected = 1'b0;
always #(posedge clk) begin
incrhistory <= { incrhistory[14:0] , increment_synched };
if (incrhistory == 16'b0011111111111111)
incr_detected <= 1'b1;
else
incr_detected <= 1'b0;
end
To detect a valid rising edge, we store a history of the last 16 values of increment_synched. When a valid steady change from 0 to 1 is produced, the history pattern will match the pattern 0011111111111111. Then, and only then, we signal it by raising incr_detected to 1. The next clock cycle, the history pattern won't match the above sequence, and incr_detected will go down to 0 again.
Prior to that, multiple bounces in the push button increment is connected to would cause many transitions, leading to many increments. Using a pattern matching like that eliminates those glitches caused by multiple bounces. With 1Khz clock as you seem to use, this pattern should be enough.
Now you can use incr_detected in your original code, incr_detected wil be 1 for just a single clk cycle.
always # (posedge clk) begin
if (incr_detected) begin
if (reg_d3 == 9)
inc_temp = 0;
else
inc_temp = reg_d3 + 1;
end
end
You can test these additions using the following simulation:
http://www.edaplayground.com/x/AQY
What you will see there is a module that takes your increment input signal from the outside, and generate a glitch-free one-cycle pulse when the input signal makes a final transition from low to high level.
Actually, I've written two versions. The second one tries to mimic the behaviour of a monostable, so the input won't be sampled for a specific period of time after the first low to high transition is detected.
You will see that the second version produces a pulse much sooner than the first version, but it's also prone to take a glitch as valid rising edge, as showed in the simulation. I'd stick with the first version then.
I have a program written in Verilog and I want to convert it into a FSM automatically. Is this possible (just to visualize it)?
Here is the code :
module pci(reset,clk,frame,irdy,trdy,devsel,idsel,ad,cbe,par,stop,inta,led_out);
input reset;
input clk;
input frame;
input irdy;
output trdy;
output devsel;
input idsel;
inout [31:0] ad;
input [3:0] cbe;
inout par;
output stop;
output inta;
output [3:0] led_out;
parameter DEVICE_ID = 16'h9500;
parameter VENDOR_ID = 16'h106d; // Sequent!
parameter DEVICE_CLASS = 24'hFF0000; // Misc
parameter DEVICE_REV = 8'h01;
parameter SUBSYSTEM_ID = 16'h0001; // Card identifier
parameter SUBSYSTEM_VENDOR_ID = 16'hBEBE; // Card identifier
parameter DEVSEL_TIMING = 2'b00; // Fast!
reg [2:0] state;
reg [31:0] data;
reg [1:0] enable;
parameter EN_NONE = 0;
parameter EN_RD = 1;
parameter EN_WR = 2;
parameter EN_TR = 3;
reg memen; // respond to baseaddr?
reg [7:0] baseaddr;
reg [5:0] address;
parameter ST_IDLE = 3'b000;
parameter ST_BUSY = 3'b010;
parameter ST_MEMREAD = 3'b100;
parameter ST_MEMWRITE = 3'b101;
parameter ST_CFGREAD = 3'b110;
parameter ST_CFGWRITE = 3'b111;
parameter MEMREAD = 4'b0110;
parameter MEMWRITE = 4'b0111;
parameter CFGREAD = 4'b1010;
parameter CFGWRITE = 4'b1011;
`define LED
`ifdef LED
reg [3:0] led;
`endif
`undef STATE_DEBUG_LED
`ifdef STATE_DEBUG_LED
assign led_out = ~state;
`else
`ifdef LED
assign led_out = ~led; // board is wired for active low LEDs
`endif
`endif
assign ad = (enable == EN_RD) ? data : 32'bZ;
assign trdy = (enable == EN_NONE) ? 'bZ : (enable == EN_TR ? 1 : 0);
assign par = (enable == EN_RD) ? 0 : 'bZ;
reg devsel;
assign stop = 1'bZ;
assign inta = 1'bZ;
wire cfg_hit = ((cbe == CFGREAD || cbe == CFGWRITE) && idsel && ad[1:0] == 2'b00);
wire addr_hit = ((cbe == MEMREAD || cbe == MEMWRITE) && memen && ad[31:12] == {12'b0, baseaddr});
wire hit = cfg_hit | addr_hit;
always #(posedge clk)
begin
if (~reset) begin
state <= ST_IDLE;
enable <= EN_NONE;
baseaddr <= 0;
devsel <= 'bZ;
memen <= 0;
`ifdef LED
led <= 0;
`endif
end
else begin
case (state)
ST_IDLE: begin
enable <= EN_NONE;
devsel <= 'bZ;
if (~frame) begin
address <= ad[7:2];
if (hit) begin
state <= {1'b1, cbe[3], cbe[0]};
devsel <= 0;
// pipeline the write enable
if (cbe[0])
enable <= EN_WR;
end
else begin
state <= ST_BUSY;
enable <= EN_NONE;
end
end
end
ST_BUSY: begin
devsel <= 'bZ;
enable <= EN_NONE;
if (frame)
state <= ST_IDLE;
end
ST_CFGREAD: begin
enable <= EN_RD;
if (~irdy || trdy) begin
case (address)
0: data <= { DEVICE_ID, VENDOR_ID };
1: data <= { 5'b0, DEVSEL_TIMING, 9'b0, 14'b0, memen, 1'b0};
2: data <= { DEVICE_CLASS, DEVICE_REV };
4: data <= { 12'b0, baseaddr, 8'b0, 4'b0010 }; // baseaddr + request mem < 1Mbyte
11: data <= {SUBSYSTEM_ID, SUBSYSTEM_VENDOR_ID };
16: data <= { 24'b0, baseaddr };
default: data <= 'h00000000;
endcase
address <= address + 1;
end
if (frame && ~irdy && ~trdy) begin
devsel <= 1;
state <= ST_IDLE;
enable <= EN_TR;
end
end
ST_CFGWRITE: begin
enable <= EN_WR;
if (~irdy) begin
case (address)
4: baseaddr <= ad[19:12]; // XXX examine cbe
1: memen <= ad[1];
default: ;
endcase
address <= address + 1;
if (frame) begin
devsel <= 1;
state <= ST_IDLE;
enable <= EN_TR;
end
end
end
ST_MEMREAD: begin
enable <= EN_RD;
if (~irdy || trdy) begin
case (address)
`ifdef LED
0: data <= { 28'b0, led };
`endif
default: data <= 'h00000000;
endcase
address <= address + 1;
end
if (frame && ~irdy && ~trdy) begin
devsel <= 1;
state <= ST_IDLE;
enable <= EN_TR;
end
end
ST_MEMWRITE: begin
enable <= EN_WR;
if (~irdy) begin
case (address)
`ifdef LED
0: led <= ad[3:0];
`endif
default: ;
endcase
address <= address + 1;
if (frame) begin
devsel <= 1;
state <= ST_IDLE;
enable <= EN_TR;
end
end
end
endcase
end
end
endmodule
If there is no automatic way, could you explain a way of doing this?
Here is an FSM made with hand but can't test so ...
Does it seem ok?
It is sometimes easier to write the code and have the documentation generated from that. Sometimes you inherit legacy code without documentation, in these situations especially if new to a language tools to help visualise what is happening can be quite useful.
With cadence tools you can run your code with 'code coverage' then imc can load the coverage data and run FSM Analysis.
I have included a simple FSM below and show the generated state diagram.
module simple_fsm();
//Inputs to FSM
logic clk;
logic rst_n;
logic [1:0] state ;
logic [1:0] nextstate;
logic turn_on ;
logic turn_off ;
localparam S_OFF = 2'b00;
localparam S_GO_ON = 2'b01;
localparam S_ON = 2'b10;
localparam S_GO_OFF = 2'b11;
// State FlipFlop
always #(posedge clk or negedge rst_n) begin
if (~rst_n) begin
state <= 2'b0;
end
else begin
state <= nextstate;
end
end
//Nextstate Logic
always #* begin
case (state)
2'd0 : if (turn_on) begin
nextstate = S_GO_ON;
end
2'd1 : nextstate = S_ON;
2'd2 : if (turn_off) begin
nextstate = S_GO_OFF ;
end
2'd3 : nextstate = S_OFF;
endcase
end
//TB clk
initial begin
#1ns;
clk = 0;
forever begin
#20ns;
clk = ~clk;
end
end
//The Test
initial begin
rst_n = 1'b0;
turn_on = 1'b0;
turn_off = 1'b0;
#(posedge clk);
#(posedge clk);
rst_n = 1'b1 ;
#(posedge clk);
turn_on = 1'b1;
#(posedge clk);
turn_on = 1'b0;
#(posedge clk);
#(posedge clk);
#100ms;
$finish();
end
endmodule
Execute with :
$ irun simple_fsm.sv -coverage all -covdut simple_fsm
$ imc &
Load cov_work (folder created by above simulation) in imc, select simple_fsm and choose FSM Analysis.
imc also helps to visualise your test coverage as well. Arcs and states that have not been hit are shown in red.
We have seen that there are some tools which can visualise the FSM, another part of the question is; is the syntax of the purposed FSM suitable for these tools.
#vermaete has reported that Modelsim SE can not see the FSM. From imc I get :
Which does not seem to cover the complexity of the code, and is shown as only having 2 reachable states, IDLE and BUSY. I would recommend if OP is going down the route of using tools to visualise, adopt a simpler (syntax) FSM structure so that the tools can parse it better.
The better and expensive simulators can detect FSM's in the code and make a visualization of it. E.g. the Modelsim SE version. These can be nice to understand code and check the coveage.
But making you're own drawing of a 6-state FSM is not that hard.
The way to check if it's OK is to write a simulation and check that the behaviour is what you want. There is no point getting a bubble diagram out and seeing if it matches your hand-drawn one, as you have no way of knowing if your hand-drawn diagram is correct...
case(segmentRead)
//-------------------
SEGMENT0: begin
READ_Ready_EEPROM <= 1'b0;
READ_RDSR_Enable <= 1'b0;
Read_Enable <= 1'b0;
READ_RDSR_DATA_REG <= 8'b0;
// READ_DATA_REG <= 8'b0;
end
//-------------------
SEGMENT2: begin
READ_RDSR_Enable <= 1'b1;
READ_RDSR_DATA_REG <= 8'b0;
end
// //-------------------
SEGMENT3: begin
READ_RDSR_Enable <= 1'b0;
READ_RDSR_DATA_REG <= RDSR_Data;
end
//-------------------
SEGMENT4: begin
Read_Enable <= 1'b1;
end
//-------------------
SEGMENT5: begin
Read_Enable <= 1'b0;
READ_DATA_REG <= Read_Data;
end
//-------------------
SEGMENT6: begin
READ_Ready_EEPROM <= 1'b1;
end
//-------------------
endcase