SL240 PROTOCOL
C.1 Overview
NOTE:
The FibreXtreme SL240 PCI, PMC, and CPCI Cards will be referred to
throughout this appendix as PMC. Anything that is exclusive to the PCI, PMC, or CPCI
Cards will be described as such.
The SL240 Serial FPDP protocol (also known as VITA 17.1) is designed to provide near
optimal throughput while maintaining low overhead. The link transfer rate for SL240
cards is 2.5 Gbps. Since an 8B/10B encoding scheme is used, this corresponds to a raw
data rate of 250 MB/s for SL240. Based on the protocol presented here, the usable
throughput of this link available to the user is 247 MB/s for SL240. All ordered sets used
by this protocol are standard Fibre Channel ordered sets with the exception of positive
IDLE, which is allowed for a more flexible receiver interface.
NOTE
: The protocol referred to throughout this document is the protocol used by the
transmitter and accepted by the receiver. The receiver does not have to see the protocol
defined here to receive data. Any generic Fibre Channel data stream with an IDLE at
least every 4096 words can be used.
C.2 Ordered Sets Used
Fibre Channel denotes a certain mapping of the transmission words in the 8B/10B
protocol to be ordered sets, which denote special control information for Fibre Channel.
These same ordered sets are used in VITA 17.1, but are assigned different meaning.
There are eighteen ordered sets used by SL240 to denote different information. Twelve of
these ordered sets are used to embed five bits of data—eight start-of-frame (SOF) sets are
used to embed three bits at the start of a frame, and four status-end-of-frame (SEOF) sets
are used to embed two bits at the end of the frame. The SOF ordered sets embed three
FPDP signals - PIO1, PIO2, and DIR.
Note that although the direction signal on FPDP is active low (/DIR), the signal
transmitted on the link is active high (DIR).
The four EOF ordered sets embed the FPDP signal NRDY (once again, the inverted
version of the FPDP interface’s /NRDY) and Transmit FIFO Overflow flag.
There are two additional EOF ordered sets used by SL240 to denote the actual end of
frame. The Mark EOF (MEOF) denotes a frame that has SYNC associated with it, and
the Frame EOF (FEOF) denotes a normal data frame. The other four ordered sets are
inter-frame padding used to denote flow control information and alternate frame
interpretations. Table C-1 shows the mappings from the Fibre Channel ordered sets onto
the VITA 17.1 ordered sets, along with the meaning associated with each ordered set.
Copyright 2006
C-1
FibreXtreme Hardware Reference Manual
Summary of Contents for FibreXtreme SL240
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