Illegal Function Call - 64K Simple ROM Cartridge

             ___     _____      ______  
    ___     / _ \\  |  __ \\   /_   _// 
   /   ||  / //\ \\ | |  \ ||   -| ||-  
  | [] || |  ___  ||| |__/ ||   _| ||_  
   \__ || |_||  |_|||_____//   /_____// 
    -|_|| `-`   `-`  -----`    `-----`  
     `-`