7
Overview
Introduction
The VMIACC-5595* is a managed hub, designed to operate with GE’s VMIxxx-5565
Reflective Memory products. Without a hub device, the Reflective Memory nodes
must be networked together in a daisy-chained loop. In the hub-less configuration if
one node becomes inoperable, the entire loop becomes disabled. When the
VMIACC-5595 hub is incorporated into the network, the network is converted from a
loop to a star configuration. In the star configuration if one node becomes inoperative,
that node is bypassed by the VMIACC-5595 and the remaining nodes on the network
remain operational. When a network consists of a large number of nodes or if the
nodes are widely dispersed over an area, the star configuration is easier to build and
maintain.
The VMIACC-5595 automatically bypasses a port when it detects a loss of signal or
the absence of a valid synchronization pattern, allowing the remaining nodes to
continue to operate. Each port on the VMIACC-5595 regenerates the serial optical
signal, eliminating problems with insertion losses and cable attenuation. Signal
regeneration also reduces jitter.
The optical ports are implemented with Small Form-Factor Pluggable (SFP)
transceivers (see Figure 1 on page 8). Only the required ports need to be populated.
The SFP transceivers can be a mix of multimode (short distance) or single-mode (long
distance) transceivers. This feature permits a cost savings in small networks, as well
as system optimization. For larger networks, several VMIACC-5595 hubs can be
cascaded, permitting a managed hub array with up to 256 nodes.
An RS232 port permits local monitoring and control of the Reflective Memory
network using a standard PC serial port. The Ethernet port (10BaseT) can be used to
monitor and control the hub from great distances through a Local Area Network
(LAN) or with the use of a Web browser.
The VMIACC-5595 is available as a 19-inch 1U rack mountable enclosure or as a
desktop enclosure. The universal power supply permits operation with nearly any
international power standard. Figure 2 on page 9 is a functional block diagram of the
VMIACC-5595 Hub Assembly.
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