how converter protocol pcm to spi

Oh well if it's what the wikipedia page looks like then it's just a parallel to serial converter with a slight twist. You just need to package your pcm codes to serial data. Opencores.org has a few different implementations of spi if you don't want to write your own. SPI is a very simple protocol though and if you don't need a generic design for it; it's just a clock and master in/master out going to slave out/slave in . You can pick a transfer size like 1 byte or 2bytes, depending on what seems optimal for your data size. Also, Since it has clock you don't have to worry about all the encoding schemes, as long as your signal is on the order of hundreds of megahertz and you stick to timequest recommendations for source synchronous designs. Your board guy would have to make sure and do things like matching impedances and pcb trace lengths if you say go above 50MHz (using LVDS would certainly help as well) or have really long traces. DCD also has IP for sale and it's a pretty easy to use SPI solution if you have some extra $$