quick help for novice - lcd code verilog

[mahdiy]

code verilog

Hey all,
From what I see there is nothing wrong with this code. It is for a hd44780 lcd, and this should initialize for 4 bit mode and then turn on the display/cursor. I get a bunch of warning for parameters without init value having a constant value of zero or something. Aren't initial values for register types always zero?

I would appreciate it if someone could take the time to look at this for me. I always see this site for google searches to various questions and it seems there are a lot of helpful people here. Thanks in advance

verilog code:

module topmod (clock, rs, re, en, databus);
	
	
	output rs, re, en;
	output reg [3:0] databus;
	input clock;
        
	reg [21:0] counter1;
	reg [10:0] dcounter;
	reg [15:0] encount;
	
	assign re = 0;
	assign rs = 0;
	reg en;
	reg flag;
	reg [1:0] state;
	reg [3:0] instr;

	
	always @ (posedge clock) 
	begin
		case(state)
		
		2'b00: begin
					counter1 <= counter1 + 1'b1;
					databus <= 0;
					en <= 0;
					if(counter1 > 2250000)
					state <= 2'b01;
				 end
		
		2'b01: begin
					case(instr)
					0: databus <= 4'b0010;
					1: databus <= 4'b0010;
					2: databus <= 4'b0000;
					3: databus <= 4'b0000;
					4: databus <= 4'b1110;
					default: flag <= 1;
					endcase
					instr <= instr + 1'b1;
					state <= 2'b10;
				 end
					
		2'b10: begin
				   if(flag)
					en <= 0;
					else
					begin
					en <= 1;
					encount <= encount + 1'b1;
					if(encount > 50000)
					begin
					encount <= 0;
					en <= 0;
					state <= 2'b11;
					end
					end
				 end
		
		2'b11: begin
					dcounter <= dcounter + 1'b1;
					if(dcounter > 2000)
					begin
					dcounter <= 0;
					state <= 2'b01;
					end
				 end
					
			
             
		endcase
		end

	

	
endmodule

 

[wanida]

initialize to zero verilog

Hi.
I'm learning myself. I have the same situation when doing counters. I use Modelsim and Quartus.
I noticed that when in Modelsim, register values don't initialize to a value unless told.
But in Quartus after programming, the hardware itself would initialize to a value and works fine.
So when writing testbenches in Modelsim, I write in such a way that the values can initialize to a definite value.

I'm still at the beginner's level so I may be wrong.

cheers.

 

[mahdiy]

verilog initialize lcd

thanks,
I also figured out the problem from before. I had to initialize some registers to zero, and a few changes I remember.

 

[aji_vlsi]

modelsim initialize register value

Hey all,
From what I see there is nothing wrong with this code. It is for a hd44780 lcd, and this should initialize for 4 bit mode and then turn on the display/cursor. I get a bunch of warning for parameters without init value having a constant value of zero or something. Aren't initial values for register types always zero?

NO, it is "x" by default. This is why in typical ASIC/FPGA designs you always use reset. Add a reset to your design, things should be fine. On some FPGAs doing it by default, that's an added feature by the tools, I recommend not to rely on it.

Ajeetha, CVC
www.cvcblr.com