I'm just starting to learn Verilog on my own after taking a course on VHDL. I'm having a trouble understanding the order in which behavioral statements are executed. Here is the code in question.
//This files is an experiment into the order in which verilog executes it's statements
module MainCircuit(clk, start);
parameter cycles = 8;
input clk;
input start;
//input [15:0] data;
integer i;
always @(posedge clk)
begin
if(start)
begin
i=0;
repeat(cycles)
begin
@(posedge clk) $display("%d\ti = %d", $time, i);
i = i + 1;
end
end
end
endmodule
module tester;
reg clk;
wire start;
assign start = 1'b1;
initial clk = 1'b0;
MainCircuit myMain(clk, start);
initial repeat(40)
begin
#5 clk = 1'b1;
#5 clk = 1'b0;
end
endmodule
and here is the output
15 i = 0
25 i = 1
35 i = 2
45 i = 3
55 i = 4
65 i = 5
75 i = 6
85 i = 7
105 i = 0
115 i = 1
125 i = 2
135 i = 3
145 i = 4
155 i = 5
165 i = 6
175 i = 7
195 i = 0
205 i = 1
215 i = 2
225 i = 3
235 i = 4
245 i = 5
255 i = 6
265 i = 7
285 i = 0
295 i = 1
305 i = 2
315 i = 3
325 i = 4
335 i = 5
345 i = 6
355 i = 7
375 i = 0
385 i = 1
395 i = 2
I don't understand why i isn't being reset to zero at each positive clock edge. Does myMain remember where it is in execution and continue from there each time clock is called? If so, where is it stopping? And how would all this be synthesized?
Two other minor question:
I tried to write start <= 1'b01; instead of assign start = 1'b01; in the second module but it wouldn't work. Why not?
the second is what's with the weird spacing in the output?
Thank you for your time.