Module Descriptions
GARD 8000 SYS RFL Electronics
April 23, 2015 6-7 973.334.3100
6.1.2.1 OVERVIEW
The GARD 8000 Controller Module offers a redundant operation mode when used in a 6U chassis.
When equipped with two Controller Modules, a GARD system can disable a faulty module and
transfer its functionality to the standby unit.
The redundant-mode control elements are effectively independent of basic GARD functions and
features. Redundancy subsystems monitor the condition of the module and take part in determining
which module is active.
When only a single Controller is present in a GARD chassis, the redundancy subsystem still continues
its monitoring, however, it has no effect on the active state of the Controller. A single module cannot
be made inactive.
6.1.2.2 RULES OF OPERATION
Two GARD Controllers present in the chassis in their dedicated slots facilitate the redundant mode of
operation. Only 6U chassis offer two controller slots. Redundant mode is not possible with a 3U
chassis.
Both Controller slots are equivalent; neither has priority. An “ACTIVE” module drives or controls the
traffic within the chassis and configures other submodules. An “INACTIVE” module does not output
any signals onto mid-plane buses.
The basic rules governing swapping between the active and inactive state were designed to be as
simple as possible and to minimize disturbances to the system and prevent swapping into a faulty or
non-existent module.
A module cannot decide by itself to become active. It can become active only if the other
Controller fails or is disabled.
A failed module does not necessary become inactive. A swap to the other module may happen
only if the other module exists and is itself not in fault. A system with Redundancy will block a
swap into a faulty module.
There are no levels or degrees of fault conditions within a Controller module. A faulty, disabled
or non-existent module is treated the same way, since its state is not trustworthy anymore.
An inactive Controller module always obtains its configuration for the chassis from the active
module – immediately after power-up and with continuing updates thereafter.
6.1.2.3 IMPLEMENTATION
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