Data Transfer - Endress+Hauser RID14 Anleitung

Operating the field indicator
timing of the bus communication via the LAS, the FF can run exact processes at regular
intervals.
Fieldbus devices, such as this field indicator, which can take over the LAS function in
the event of failure of the primary master, are called ' L ink Masters' . In contrast, ' B asic
Devices' can only receive signals and send them to the central process control system.
The LAS function is deactivated in this field indicator when the unit is delivered.

6.3.3 Data transfer

We distinguish between two types of data transfer:
• Scheduled data transfer (cyclic): all time-critical process data (i.e. continuous
measurement or actuating signals) are transferred and processed in accordance with a fixed
schedule.
• Unscheduled data transfer (acyclic): 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.
6.3.4 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.
The FOUNDATION Fieldbus™ uses addresses between 0 and 255:
• 0 to 15 are reserved.
• 16 to 247 are available for permanent devices. Some host systems may further subdivide this
range. This range is typically shortened for efficiency.
• 248 to 251 are available for devices with no permanent address such as new devices or
decommissioned devices.
• 252 to 255 are available for temporary devices, such as handhelds.
The field device tag name (PD_TAG) is given to the device in question during commissioning
(see Operating Instructions). It remains stored in the device even during a supply voltage failure.
6.3.5 Function blocks
The FOUNDATION Fieldbus™ uses predefined function blocks to describe the functions of a
device and to specify uniform data access. The function blocks implemented in each fieldbus
device provide information on the tasks which a device can accept in the whole of the
automation strategy.
In the case of sensors these are typically the following blocks:
• 'Analog Input' or
• 'Discrete Input' (digital input)
Actuating valves normally have the function blocks:
• 'Analog Output' or
• 'Discrete Output' (digital output)
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RID14
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