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STB NIP 2212 Web Server
890USE17700 April 2004 77
Configuring Master Controllers
Introduction Any controller on the Ethernet network has the potential to become the master of an
island on that network. Mastery can be obtained on a first-come/first-serve basis.
The STB NIP 2212 allows you to pre-assign mastery to as many as three specific
controllers on the network. If one of these assigned controllers is connected, it will
take mastery over any unassigned controllers, even if an unassigned controller has
connected to the island first. To assign one or more master controllers, use the
Master Controller web page.
Understanding
Processing
Mastery
A controller that has mastery over an island has the ability to write to the island’s
output process image and to change operating parameters on the island nodes..
Typically, the first controller to request write access is granted mastery. If another
master attempts to write to the island while the first controller has mastery, the NIM
sends an error message and access is denied.
If a master controller has been configured on the Master Controller web page (See
Sample Master Controller Web Page, p. 78), a write request from it will pre-empt
processing mastery from any other device during its reservation time.
Fields on the
Master
Controller Web
Page
To pre-assign one or more (up to three) master controllers for the STB NIP 2212,
identify them by their IP addresses:
Field Name Description
Master x ID* The unique IP address (See How the STB NIP 2212 Obtains IP Parameters,
p. 60) for a master controller.
reservation
time
The amount of time in ms allocated to a master controller for writing to the
STB NIP 2212. Other controllers attempting to write to the STB NIP 2212
while the master is connected will receive an error message.
The default reservation time is 60,000 (1 min). Each time the master writes to
the NIM, the reservation time is reset to 60,000.
holdup time The amount of time in ms that output modules will hold their current state
without an update by a Modbus write command (See List of Supported
Commands, p. 135). When the module hold-up time out expires, the outputs
will be driven to their defined fallback states (See Island Fallback Scenarios,
p. 161).
Note: The holdup time must be defined via the Master Controller web page.
Holdup time out parameters and values are stored in nonvolatile Flash
memory.
* If you do not enter an IP address, then write access to the NIM will be obtained by the first
master that writes to it.