RFL IMUX 2000 - 3.1.4 SCB CONFIGURATION MIRRORING.; 3.1.5 RULES OF BEHAVIOR.

Because RFL™ and Hubbell® have a policy of continuous product improvement, we reserve the right to change designs and specifications without notice.
3.1.4 SCB CONFIGURATION MIRRORING.
An inactive common module (Main or Standby) must obtain its shelf configuration information from
the active module. This allows installing any spare module to replace a failed unit. If a newly inserted
module became active without configuration transfer, it could disrupt the multiplexer or channel
modules.
Configuration transfer is accomplished by means of an SCB “mirror” circuit, using the backplane
control bus. The inactive common module continuously captures SCB messages and updates a mirror
table, duplicating configuration tables of the active module. Upon becoming active, the module can
seamlessly take over shelf control.
Upon becoming inactive (after switchover or power-up), a CM4 considers itself not configured. The
front-panel CONFIGURED indicator being extinguished indicates this state. After capturing initial
configuration message cycles from the backplane, an inactive CM4 is considered configured. It will
continue updating its configuration mirror by following the active card as it is reconfigured. Obviously,
when changing configuration parameters, the user must allow some time (about 20 seconds) for the
values to be reliably transferred into an inactive module.
The not-configured state of the mirror (CONFIGURED LED off) does not affect redundant decision-
making, but serves as a warning to the operator that it may not be desired to have the module become
active yet. Automatic switchover can take place regardless of the mirror status. An operator can
prevent it by sliding the front-panel mode switch into desired “forced” setting.
It is up to the operator who is physically installing a replacement CM4 to decide whether it is
appropriate to allow the new unit to become active without configuration successfully mirrored. The
replacement, by design, cannot wait for configuration before attempting an automatic swap. The lack
of incoming data could possibly be caused by a failure of the protected module.
3.1.5 RULES OF BEHAVIOR.
Redundant operation modes result in the same operational behavior, whether switched by internal
trouble detectors or forced by the front panel slide switch or a remote command.
Table 3-1. Redundant operation, rules of behavior
TYPE OF
OPERATION
MAIN MODULE STANDBY MODULE
NORMAL
OPERATION
IMUX 2000E1 RFL Electronics Inc.
• ACTIVE
• Drives MUX bus.
• Communicates over SCB.
• Communicates with outside
.
• INACTIVE
• Off MUX bus.
• Communicates over SCB, only if no internal
trouble.
• Captures curren
t
active configuration into
mirror tables.
• No independent communication with outside.
SWAPPED
OPERATION
• INACTIVE
• Off MUX bus.
• Does not communicate over SCB.
• Captures current active configuration into
mirror tables.
• No independent communication with outside.
• ACTIVE
• Drives MUX bus.
• Communicates over SCB.
• Communicates with outside
.
January 23, 2004 3-7 (973) 334-3100