How do you plan to solve it?
module error_checker_xz(
input [7:0]bus,
output reg all_known, has_unknown,
output reg [7:0] bus_if_known
);
always @ (*)
begin
if((^bus==0) || (^bus==0) || (^bus==1) || (^bus==1))
begin
all_known = 1;
has_unknown = 0;
bus_if_known = bus;
end
else if((bus === 8'bzzzzzzzz) || (bus === 8'bxxxxxxxx))
begin
all_known = 0;
has_unknown = 1;
bus_if_known = 8'h00;
end
else if((bus == 8'b00000000) || (bus == 8'b11111111))
begin
all_known = 1;
has_unknown = 0;
bus_if_known = bus;
end
else
begin
all_known=0;
has_unknown=1;
bus_if_known=8'h00;
end
end
endmodule