Function Blocks; Fieldbus Based Process Control; Device Description - Endress+Hauser iTEMP TMT 165 FOUNDATION Fieldbus Betriebsanleitung

5 Operation
2
96
The FOUNDATION Fieldbus uses addresses between 0 and 255:
• Groups/DLL: 0...15
• Devices in operation: 20...35
• Reserve devices: 232...247
• Offline/substitute devices: 248...251
The field device tag name (PD_TAG) is given to the device in question during
commissioning (see page 98). It remains stored in the device even during a power
supply failure.

5.1.5 Function Blocks

The FOUNDATION Fieldbus uses predefined function blocks to describe the functions
of a device and to specify uniform data access (chapter 11). 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:
• 'Analogue Input' or
• 'Discrete Input' (digital input)
Actuating valves normally have the function blocks:
• 'Analogue Output' or
• 'Discrete Output' (digital output)
For control tasks there are the blocks:
• PD controller or
• PID controller
Note:
More information on this can be found on page 111.

5.1.6 Fieldbus based process control

With the FOUNDATION Fieldbus field devices can carry out simple process control
functions themselves, thereby relieving pressure on the superior process control
system. Here the Link Active Scheduler (LAS) coordinates data exchange between the
sensor and controller and makes sure that two field devices cannot access the bus at
the same time.
To do this, configuration software such as the NI-FBUS Configurator from National
Instruments is used to connect the various function blocks to the desired control
strategy – generally graphically (see page 100).

5.1.7 Device description

For commissioning, diagnosis, configuration etc. make sure that process control
systems or superior configuration systems can access all device data and that the
operating structure is uniform.
The device-specific information required for this is stored as so-called device
description data in special files (the 'Device Description'- DD). This enables the device
data to be interpreted and shown via the configuration programme. The DD is thus a
kind of 'device driver'.
Predefined standard DDs are available for the basic functions of measuring devices and
these can be ordered from Fieldbus FOUNDATION. Expanded device descriptions are
always required if a manufacturer has implemented additional functions and
parameters in his measuring device.
On the other hand, a CFF file (CFF = Common File Format) is required for the network
configuration in ON-line and OFF-line mode. These files are available from the device
manufacturer.
FOUNDATION Fieldbus temperature transmitter
Endress+Hauser