Curtiss-Wright GT200 VME, Справочник по аппаратуре

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OPERATION
Valid node IDs range from 0 to 255. However, node ID 0 is used by default when boards
are first powered on, using ID 0 is not recommended. The node ID is software
programmable.
NOTE: It is possible the architecture will treat network traffic originating from node
ID 0x00 differently to reduce effects from improperly initialized nodes. Consequently,
the number of nodes supported is 255.
The maximum fiber length supported is 10 km based on the ring size, media used, and
status messaging.
4.2.5 Interface Standards
The GT200 interface is a proprietary interface running at 2.5Gbps. The interface uses
both 8B/10B encoding and CRC32 error checking.
4.2.6 Network Framing
Frame types include:
•
Variable length data frame
•
Sub-length data frame (for transactions less than 32-bits)
Frames are of variable-length with support for payload sizes as integer multiples of four
bytes. Payload size can range from a 4-byte minimum to a 128-byte maximum. Network
logic transparently handles appropriate generation of framing, including length selection.
Framing overhead includes delimiters, source node ID, age, address, and other control
functions.
Sub-length data frames include 32-bits of data with four independent byte enables to
support transfer sizes less than 32 bits, preserving the concept of memory transparency.
4.2.7 Link Interface
•
Laser Enable (one per link)
•
Link Select-Link Up
•
Laser Signal Detect (one per link)
4.2.8 Network Throughput
The maximum network write throughput is approximately 205 MBps (base10).
4.2.9 Error Detection
All network frames include a Cyclical Redundancy Check (CRC) to facilitate error
detection in the network receiver interface.
The CRC is automatically verified by network hardware without user intervention. In
addition, the end of frame delimiter incorporates flags for CRC errors such that a detected
CRC error on one node is detectable on other downstream nodes, even though the frame
may have been modified (corrected) in the retransmission process. The network also
includes other error detection mechanisms, such as an invalid transmission word
encountered during the decoding process. Network errors include CRC error, encoding
error, framing error, and expired message error.
Copyright 2005 4-3 GT200 VME Hardware Reference