SCRAMNET OVERVIEW
Copyright 2007
2-11
S SC150e HARDWARE REFERENCE
WIRE LOOPBACK MODE
The Wire Loopback mode needs no manual external modifications to work. Wire
Loopback is enabled by setting CSR2[7] ON. This mode checks the on-card circuitry for
continuity.
NOTE
: If a node is inserted into the network while in wire loopback mode, it will
create a break in the network ring, making all nodes down-line unreachable.
MECHANICAL SWITCH (MEDIA CIRCUITRY) LOOPBACK MODE
Mechanical Switch (Media Circuitry) Loopback mode is enabled by setting Mechanical
Switch Override CSR8[11] to OFF. This test is used to check the media circuitry but
excludes the fiber-optic circuitry. In this test the signal does not leave the Media circuitry.
FIBER-OPTIC LOOPBACK MODE
A valid Fiber-optic Loopback
mode must have the optional Fiber Optic Bypass Switch
connected, Disable Fiber-optics Loopback CSR2[6] set to OFF (power up default), and
the Insert Node CSR0[15] enabled. When the Fiber-optic Loopback
mode is in effect, the
output of the transmitter is connected by fiber optics directly to the input of the receiver,
and the receiver is disconnected from the network.
The optional Fiber Optic Bypass Switch must be installed for this loopback to work.
However, in the absence of the Fiber Optic Bypass Switch, fiber-optic cables could be
run from the node’s transmitter output connectors to the receiver input connectors. This
configuration, with Insert Node enabled, would constitute a Fiber-optic Loopback mode
for stand-alone testing. Set CSR2[6] ON to disable the Fiber-optic Loopback mode when
the node is in use as a part of the network. This configuration is not a substitute for the
Fiber Optic Bypass Switch for network operation.
2.9.5 Write-Me-Last Mode
The Write-Me-Last mode of operation allows the originating node to be the last node in
the ring to have the data deposited to its memory. This can be useful for synchronization.
This means that when the host performs a write to the S SC150e shared
memory, the data is not immediately written to the host node’s memory, but is first sent to
the other nodes on the network. When the message returns to the originating node it is
written to shared memory, and is then removed from the network ring.
Therefore, host-originated data written to shared memory travels the ring updating the
S SC150e node memories. Upon returning to the originating node, the node
writes the data to its own shared memory as the last node on the ring. This guarantees that
the data is available on all other nodes.
Summary of Contents for SCRAMNet+ SC150e
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