Link Active Scheduler (Las); Data Transfer; Device Id, Addressing - Endress+Hauser iTEMP TMT 165 FOUNDATION Fieldbus Betriebsanleitung

FOUNDATION Fieldbus temperature transmitter
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Endress+Hauser
• If using fieldbus devices in a hazardous area, the H1 bus must be equipped with an
intrinsically safe barrier before the transition to the hazardous area.
• A bus terminator is required at each end of the bus segment.
High Speed Ethernet (HSE):
The superior H2 bus system is realised via the High Speed Ethernet (HSE) with a
transmission rate of max. 100 MBit/s. This serves as the 'backbone' (basic network)
between various local sub-networks and/or where there are a large number of network
users.

5.1.2 Link Active Scheduler (LAS)

The FOUNDATION Fieldbus works according to the 'producer-consumer' relationship.
This provides various advantages.
Data can be directly exchanged between field devices, e.g. a sensor and an actuating
valve. Each bus user 'publishes' its data on the bus and all the bus users configured
accordingly obtain this data. Publication of this data is carried out by a 'bus
administrator' known as the 'Link Active Scheduler', which controls the sequence of bus
communication centrally. The LAS organises all the bus activities and sends
appropriate commands to the individual field devices.
Other tasks of the LAS are:
• Recognition and reporting of newly connected devices.
• Reporting the removal of devices no longer communicating with the fieldbus.
• Keeping the 'Live List'. This list, in which all the fieldbus users are recorded, is
checked by the LAS regularly. New or removed devices are immediately transferred
to the Live List and sent to all the devices.
• Requesting process data from the field devices in accordance with a fixed schedule.
• Allocation of send rights (tokens) to devices between the untimed data transfer.
The LAS can be run redundantly, i.e. it exists both in the process control system and in
the field device. If one LAS fails, the other LAS can accurately take over communication.
Through precise timing of the bus communication via the LAS, the FF can run exact
processes at regular intervals. (Deterministic).
Note:
Fieldbus devices such as the TMT 165, which can take over the LAS function in the
event of failure of the primary master, are called 'Link Master'. In contrast, 'Basic
Devices' can only receive signals and send them to the central process control system.
They do not have the capability to become the LAS function.

5.1.3 Data transfer

We distinguish between two types of data transfer:
• l|~}Ž…~} }zz ‹z‡Œ~‹ A|’|…‚|BS all time-critical process data (i.e. continuous
measurement or actuating signals) are transferred and processed in accordance with
a fixed schedule.
• n‡Œ|~}Ž…~} }zz ‹z‡Œ~‹ Az|’|…‚|BS device parameters that are not time-critical for
the process and diagnosis information are only transferred to the fieldbus when
needed. This data transfer is always carried out in the intervals between timed
communication.

5.1.4 Device ID, addressing

Within the FF network, each fieldbus device is identified by a unique device ID
(DEVICE_ID).
The fieldbus host system (LAS) automatically gives the network address for this to the
field device. The network address is the address that the fieldbus currently uses.
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