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Manual
00809-0500-4880
Resource blocks
Resource blocks contain the hardware specific characteristics associated with a
device; they have no input or output parameters.
The algorithm within a resource block monitors and controls the general
operation of the physical device hardware. The execution of this algorithm is
dependent on the characteristics of the physical device, as defined by the
manufacturer. As a result of this activity, the algorithm may cause the generation
of events. There is only one resource block defined for a device. For example,
when the mode of a resource block is out of service, it impacts all of the other
blocks.
Transducer blocks
Transducer blocks connect function blocks to local input/output functions.
They read sensor hardware and write to effector (actuator) hardware. This
permits the transducer block to execute as frequently as necessary to obtain good
date from sensors and ensure proper writes to the actuator without burdening
the function blocks that use the data. The transducer block also isolates the
function block from the vendor specific characteristics of the physical I/O.
Alerts
When an alert occurs, execution control sends an event notification and waits a
specified period of time for an acknowledgement to be received.
This occurs even if the condition that caused the alert no longer exists. If
acknowledgement is not received within the pre-specified time-out period, the
event notification is retransmitted. This assures that alert messages are not lost.
Two types of alerts are defined for the block: events and alarms. Events are used
to report a status change when a block leaves a particular state, such as when a
parameter crosses a threshold. Alarms not only report a status change when a
block leaves a particular state, but also report when it returns back to that state.
8.2
Network communication
Figure 8-2
(link).
Rosemount OCX8800A
illustrates a simple Fieldbus network consisting of a single segment
F
Fieldbus
™
OUNDATION
December 2022
117
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