The packet over SONET/SDH physical layer (POS-PHY) Level 4 interface, first developed by the SATURN Development Group, was later adopted by the Optical Internetworking Forum (OIF) as the System Packet Interface Level 4—Phase 2 (SPI-4.2). Therefore, POS-PHY Level 4 and SPI-4.2 are synonymous.
The POS-PHY Level 4 MegaCore® function uses the SPI-4.2 interface for high-speed cell and packet transfers between PHY and link-layer devices. The SPI-4.2 interface supports a data width of 16 bits (LVDS solution), and can be a PHY-link, link-link, link-PHY, or PHY-PHY connection in multi-gigabit applications, including ATM and POS (STS-192/STM-64), 10-gigabit Ethernet, and multi-channel gigabit and fast Ethernet.
- Configurable datapath width (32 bits, 64 bits, 128 bits)
- Supports up to 256 ports
- POS-PHY Level 4 MegaCore function throughput rate:
- From 840 Mbps to 1,250 Mbps per LVDS lane for Stratix® series FPGAs and HardCopy® series ASICs
- Up to 840 Mbps per LVDS lane for Arria® GX series FPGAs
- From 250 Mbps per LVDS lane (32-bit system datapath) to 622 Mbps (64-bit system datapath) for Cyclone® series FPGAs
- Fixed start of packet (SOP) alignment to the most significant byte lane eases subsequent packet processing
- FIFO buffer status management and indications
- Run-time programmable calendar length, burst size, and threshold levels
- Asymmetric ports and hitless bandwidth re-provisioning
- Error detection and handling
- Easy-to-use intellectual property (IP) Toolbench interface and functional simulation models in Verilog and VHDL