module counter #(
parameter int unsigned WIDTH = 2,
parameter bit [WIDTH-1:0] MAX_COUNT = '1,
parameter bit [WIDTH-1:0] MIN_COUNT = '0,
parameter bit [WIDTH-1:0] INITIAL_COUNT = MIN_COUNT,
parameter bit WRAP_AROUND = 1,
localparam type COUNT = logic [WIDTH-1:0]
) (
input var logic i_clk,
input var logic i_rst,
input var logic i_clear,
input var logic i_set,
input var COUNT i_set_value,
input var logic i_up,
input var logic i_down,
output var COUNT o_count,
output var COUNT o_count_next,
output var logic o_wrap_around
);
function automatic COUNT count_up(
input var COUNT current_count
) ;
if (current_count == MAX_COUNT) begin
if (WRAP_AROUND) begin
return MIN_COUNT;
end else begin
return MAX_COUNT;
end
end else begin
return current_count + 1;
end
endfunction
function automatic COUNT count_down(
input var COUNT current_count
) ;
if (current_count == MIN_COUNT) begin
if (WRAP_AROUND) begin
return MAX_COUNT;
end else begin
return MIN_COUNT;
end
end else begin
return current_count - 1;
end
endfunction
function automatic logic get_wrap_around_flag(
input var logic clear ,
input var logic set ,
input var logic up ,
input var logic down ,
input var COUNT current_count
) ;
logic [2-1:0] up_down;
up_down = {up, down};
if (clear || set) begin
return '0;
end else if ((current_count == MAX_COUNT) && (up_down == 2'b10)) begin
return '1;
end else if ((current_count == MIN_COUNT) && (up_down == 2'b01)) begin
return '1;
end else begin
return '0;
end
endfunction
function automatic COUNT get_count_next(
input var logic clear ,
input var logic set ,
input var COUNT set_value ,
input var logic up ,
input var logic down ,
input var COUNT current_count
) ;
case (1'b1)
clear : return INITIAL_COUNT;
set : return set_value;
(up && (!down)): return count_up(current_count);
(down && (!up)): return count_down(current_count);
default : return current_count;
endcase
endfunction
COUNT count ;
COUNT count_next;
always_comb o_count = count;
always_comb o_count_next = count_next;
always_comb count_next = get_count_next(i_clear, i_set, i_set_value, i_up, i_down, count);
always_ff @ (posedge i_clk, negedge i_rst) begin
if (!i_rst) begin
count <= INITIAL_COUNT;
end else begin
count <= count_next;
end
end
if ((WRAP_AROUND)) begin :g
always_comb o_wrap_around = get_wrap_around_flag(i_clear, i_set, i_up, i_down, count);
end else begin :g
always_comb o_wrap_around = '0;
end
endmodule
module gray_encoder #(
parameter int unsigned WIDTH = 32
) (
input var logic [WIDTH-1:0] i_bin,
output var logic [WIDTH-1:0] o_gray
);
always_comb o_gray = i_bin ^ (i_bin >> 1);
endmodule
module gray_counter #(
parameter int unsigned WIDTH = 2,
parameter bit [WIDTH-1:0] MAX_COUNT = '1,
parameter bit [WIDTH-1:0] MIN_COUNT = '0,
parameter bit [WIDTH-1:0] INITIAL_COUNT = MIN_COUNT,
parameter bit WRAP_AROUND = 1,
localparam type COUNT = logic [WIDTH-1:0]
) (
input var logic i_clk,
input var logic i_rst,
input var logic i_clear,
input var logic i_set,
input var COUNT i_set_value,
input var logic i_up,
input var logic i_down,
output var COUNT o_count,
output var COUNT o_count_next,
output var logic o_wrap_around
);
COUNT bin_count ;
COUNT bin_count_next;
counter #(
.WIDTH (WIDTH ),
.MAX_COUNT (MAX_COUNT ),
.MIN_COUNT (MIN_COUNT ),
.INITIAL_COUNT (INITIAL_COUNT),
.WRAP_AROUND (WRAP_AROUND )
) u_bin_counter (
.i_clk (i_clk ),
.i_rst (i_rst ),
.i_clear (i_clear ),
.i_set (i_set ),
.i_set_value (i_set_value ),
.i_up (i_up ),
.i_down (i_down ),
.o_count (bin_count ),
.o_count_next (bin_count_next),
.o_wrap_around (o_wrap_around )
);
gray_encoder #(
.WIDTH (WIDTH)
) u_gray_cur (
.i_bin (bin_count),
.o_gray (o_count )
);
gray_encoder #(
.WIDTH (WIDTH)
) u_gray_next (
.i_bin (bin_count_next),
.o_gray (o_count_next )
);
endmodule
module Top (
input var logic clk ,
input var logic rst ,
input var logic i_up ,
output var logic [32-1:0] o_count
);
gray_counter #(
.WIDTH (32 )
) u (
.i_clk (clk ),
.i_rst (rst ),
.i_clear (1'b0 ),
.i_set (1'b0 ),
.i_set_value (32'b0 ),
.i_up (i_up ),
.i_down (1'b0 ),
.o_count (o_count),
.o_count_next ( ),
.o_wrap_around ( )
);
endmodule