SerialFPDP (VITA 17.1) A High Performance Lightweight Data Link Protocol

Most protocols for high speed cable interconnects are not designed for real time, streaming data applications. Instead, most interconnect protocols target large networking and communications infrastructure. This generally requires the protocol to limit packet size, perform complex negotiations when establishing source/destination connections, and adhere to high level arbitration and prioritization mechanisms. Often combined with backwards compatibility requirements, this results in the protocol having several complex networking layers of overhead that are not only unnecessary for real time applications, but unacceptable in terms of performance.

Alternatively, Serial FPDP is primarily hardware based and optimized for large data transfers, minimal CPU utilization, and low latency, deterministic applications. These characteristics have lead to its wide spread popularity for C4ISR (command, control, communications, computers, intelligence, surveillance, and reconnaissance) deployments including:

• Synthetic Aperture and Phased Array Radar
• Signal Intelligence (SIGINT, COMINT, and ELINT)
• Sonar
• Other target applications include medical, semiconductor, and seismic imaging.
  

Supporting point-to-point, broadcast chaining, and single or multiple master ring topologies, Serial FPDP is rapidly becoming the interconnect of choice for streaming sensor signal processing systems. By serializing FPDP data streams, it supports connections of up to 10 kilometers, providing the ability to place great distances between processing elements and sensor subsystems.

On the transmit side, parallel FPDP data is converted to Serial FPDP. On the receive side, Serial FPDP data is converted to parallel FPDP. The first step of this transmission and conversion process involves input FPDP data made up of 32-bit words that pass through a transmit FIFO to an 8B/10B encoder, with data then serialized, and sent over a fiber or copper wire. On the receive side, data is deserialized, then decoded, and sent to receive FIFO’s before being provided as FPDP output data.

Serial FPDP utilizes the Fibre Channel link layer protocol for data transport. Using a subset of the link layer’s 8G/10B encoding scheme, ordered sets are modified for Serial FPDP protocol but commercially available Fibre Channel IC’s can be utilized to interface to the physical media.

In addition to transmitting standard FPDP 32-bit data words, Serial FPDP also transmits FPDP control signals. The protocol supports flow control and three primary types of frames: data frame, SYNC frame, and SYNC without data frame. With variable size frames consisting of up to 512, 32-bit words per frame, Serial FPDP data overhead is less than 2%. In a 512, 32-bit word frame, only six words are allocated to overhead.