Up Counter can be defined in a simple way don't you think ?
It just counts. HaHa
Yes!! A counter just counts up to the maximum decimal value when all the required bits are 1.
Crazy Definition ? I agree. Let me elaborate.
Let's take an example of 3 bit counter. So whats the maximu of 3bit counter i.e when all bits are 1 in other words "111" It's 7.
Similarly for 4 bits it "1111"that is 15.
Thus n-bits we require n Flip Flops.
Thus an Up counter will count from 0 upto the maximum as I have stated ad will again start from 0.
Lets code for a 4-bit Up Counter
module up(out,en,clk,reset); output reg[7:0] out; input en, clk, reset; initial out = 0; always @(posedge clk)begin if (reset) begin //if reset is true out <= 8'b0 ; end else if (en==1 && out<15) //if enable is high // because 1111 is 15 out <= out + 1; else out <= 0; end endmodule //*************************TestBench module uptest(); reg en; reg clk; reg reset; wire [7:0]out; initial begin reset=0; clk=0; en=1; #80 en=0; end up call(out,en,clk,reset); always #2 clk=!clk; endmodule
Here is the output
Notice after 80ns output is zero because I have set en pin to 0 in testbench.Thus change your value of max and design your own counter.