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Reference Manual
00809-0400-4728, Rev AA
June 2011
3-3
Rosemount 644
NOTE
When an upstream block is set to OOS, this will impact the output status of all
downstream blocks. The figure below depicts the hierarchy of blocks:
Link Active Scheduler The 644 can be designated to act as the backup Link Active Scheduler (LAS)
in the event that the designated LAS is disconnected from the segment. As
the backup LAS, the 644 will take over the management of communications
until the host is restored.
The host system may provide a configuration tool specifically designed to
designate a particular device as a backup LAS. Otherwise, this can be
configured manually as follows:
1. Access the Management Information Base (MIB) for the 644.
To activate the LAS capability, write 0x02 to the
BOOT_OPERAT_FUNCTIONAL_CLASS object (Index 605). To
deactivate, write 0x01.
2. Restart the device.
Block Installation Rosemount devices are pre-configured with function blocks at the factory, the
default permanent configuration for the 644 is listed below. The 644 can have
up to ten additional instantiated function blocks.
• 2 Analog Input Blocks (tag names AI 1300, AI 1400)
• 1 Proportional/Integral/Derivative Block (tag name PID 1500)
The 644 supports the use of Function Block Instantiation. When a device
supports block instantiation, the number of blocks and block types can be
defined to match specific application needs.The number of blocks that can be
instantiated is only limited by the amount of memory within the device and the
block types that are supported by the device. Instantiation does not apply to
standard device blocks like the Resource, Sensor Transducer, LCD
Transducer, and Advanced Diagnostics Blocks.
By reading the parameter “FREE_SPACE” in the Resource block you can
determine how many blocks you can instantiate. Each block that you
instantiate takes up 4.5% of the “FREE_SPACE.”
Block instantiation is done by the host control system or configuration tool, but
not all hosts are required to implement this functionality. Please refer to your
specific host or configuration tool manual for more information.
Resource
Block
Transducer
Block
Analog Input
(AI Block)
Other
Function
Blocks