Basic start for the control block

.gitignore

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+*.vvp
+*.vpi
+*.lx2
+*.o

cpu/Makefile

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+SOURCES=processor.v testbench.v
+VVP=processor.vvp
+
+.PHONY: run
+run: ${VVP}
+	vvp ${VVP}
+
+.PHONY: build
+build: ${VVP}
+
+.PHONY: wave
+wave: ${VVP}
+	vvp ${VVP} -lxt2
+	gtkwave test.lx2 gtkwave_savefile.gtkw
+
+${VVP} : ${SOURCES}
+	iverilog -g2012 $^ -o $@
+
+.PHONY: clean
+clean:
+	rm -f ${VVP} test.lx2

cpu/gtkwave_savefile.gtkw

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+[*]
+[*] GTKWave Analyzer v3.3.104 (w)1999-2020 BSI
+[*] Wed Feb  8 09:14:55 2023
+[*]
+[dumpfile] "/home/user/UNI_DATA/COMS30046_2022_TB-2/projects/9086/cpu/test.lx2"
+[dumpfile_mtime] "Wed Feb  8 09:14:04 2023"
+[dumpfile_size] 334
+[savefile] "/home/user/UNI_DATA/COMS30046_2022_TB-2/projects/9086/cpu/gtkwave_savefile.gtkw"
+[timestart] 0
+[size] 1630 1059
+[pos] -1 -1
+*-20.669413 0 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
+[treeopen] tb.
+[sst_width] 221
+[signals_width] 110
+[sst_expanded] 1
+[sst_vpaned_height] 313
+@28
+tb.p.clock[0]
+tb.p.reset[0]
+tb.p.start[0]
+@29
+tb.p.state[1:0]
+[pattern_trace] 1
+[pattern_trace] 0

cpu/processor.v

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+`timescale 1ns/1ps
+
+module clock_gen (input enable, output reg clk);
+  
+  parameter FREQ = 1000;  // in HZ
+  parameter PHASE = 0; 		// in degrees
+  parameter DUTY = 50;  	// in percentage 
+  
+  real clk_pd  		= 1.0/FREQ * 1000000; 	// convert to ns
+  real clk_on  		= DUTY/100.0 * clk_pd;
+  real clk_off 		= (100.0 - DUTY)/100.0 * clk_pd;
+  real quarter 		= clk_pd/4;
+  real start_dly        = quarter * PHASE/90;
+  
+  reg start_clk;
+  
+  initial begin
+  end
+  
+  // Initialize variables to zero
+  initial begin
+    clk <= 0;
+    start_clk <= 0;
+  end
+  
+  // When clock is enabled, delay driving the clock to one in order
+  // to achieve the phase effect. start_dly is configured to the 
+  // correct delay for the configured phase. When enable is 0,
+  // allow enough time to complete the current clock period
+  always @ (posedge enable or negedge enable) begin
+    if (enable) begin
+      #(start_dly) start_clk = 1;
+    end else begin
+      #(start_dly) start_clk = 0;
+    end      
+  end
+  
+  // Achieve duty cycle by a skewed clock on/off time and let this
+  // run as long as the clocks are turned on.
+  always @(posedge start_clk) begin
+    if (start_clk) begin
+      	clk = 1;
+      
+      	while (start_clk) begin
+      		#(clk_on)  clk = 0;
+    		#(clk_off) clk = 1;
+        end
+      
+      	clk = 0;
+    end
+  end 
+endmodule
+
+
+module processor ( input clock, input reset );
+  reg [1:0] state;
+  reg start=0;
+
+  always @(negedge reset) begin
+    if (reset==0) begin
+      @(posedge clock);
+      state=0;
+      #10
+      start=1;
+      //while (reset==0) begin
+      //end
+      //while (clock==0) begin
+      //end// skip this half-way through clock cycle
+      //start=1;
+    end
+  end
+
+  always @(posedge clock) begin
+    if (clock && start==1) begin
+	    state=state+1;
+  end
+end
+
+
+endmodule

cpu/testbench.v

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+module tb;
+  wire clock;
+  reg reset;
+  reg  clk_enable;
+
+  processor p(clock,reset);
+  
+  clock_gen #(.FREQ(1000)) u1(clk_enable, clock);
+
+  initial begin
+    $dumpfile("test.lx2");
+    $dumpvars(0,p);
+    clk_enable <= 1;
+
+    #($random%500)
+    reset = 0;
+    #(100) 
+    reset = 1;
+    #(10000)
+
+    #50 $finish;
+  end
+endmodule