Illegal Function Call - 64K Simple ROM Cartridge

             ___      ______   _    _   
  ____      / _ \\   /_   _// | || | || 
 |    \\   / //\ \\  `-| |,-  | || | || 
 | [] ||  |  ___  ||   | ||   | \\_/ || 
 |  __//  |_||  |_||   |_||    \____//  
 |_|`-`   `-`   `-`    `-`'     `---`   
 `-`