
Open Core Protocol

The Open Core Protocol (OCP) is a protocol for on-chip subsystem communications.
It is an openly licensed, core-centric protocol and defines a bus-independent, configurable interface. OCP International Partnership (OCP-IP) produces OCP specifications. OCP data transfer models range from simple request-grant handshaking through pipelined request-response to complex out-of-order operations.
Legacy IP cores can be adapted to OCP, while new implementations may take advantage of advanced features: designers select only those features and signals encompassing a core’s specific data, control and test configuration. 
The Open Core Protocol (OCP) is one of several FPGA processor interconnects used to connect soft FPGA peripherals to FPGA CPUs --
both soft microprocessor and hard-macro processor.
Other such interconnects include
Advanced eXtensible Interface (AXI),
Avalon,
and the Wishbone bus.
FPGA vendor Altera joined the Open Core Protocol International Partnership in 2010.