User Manual Owner's manual

Publication 1757-UM006A-EN-P - May 2002
7-10 Using the 1788-CN2FF, ControlNet-to-FOUNDATION Fieldbus H1 Linking Device
ControlNet Discrete Input Objects
The linking device creates an instance of a ControlNet DI object for
every wired channel in the MDI block instances. Each instance of the
ControlNet DI object has the attributes and access rules shown in
Table 7.C.
All attributes in Table 7.C are created if a standard Fieldbus DI
function block is connected to a channel on an MDI block. Otherwise,
DiscAlmFlag is not created.
Alarm Handling for Discrete Inputs
You can configure Fieldbus DI function blocks to detect and report
alarms.
The process alarm (DISC_ALM) are exposed through the ControlNet
DI object. When you connect a DI function block to an MDI block,
the NI-FBUS Configurator configures the field device to send the
alarm to the linking device.
In Fieldbus terminology, confirming an alarm means that the alarm
has been received by an operator, and acknowledging an alarm
means that the operator has taken the necessary action.
When an alarm condition is detected by a Fieldbus function block, the
alarm is said to be ACTIVE. An active alarm should be Acknowledged
and Confirmed after the condition causing the alarm is corrected.
When the function block detects the alarm condition is no longer
present, the alarm is said to be CLEARED. The CLEARED state must be
Confirmed when it is detected. Users of the LD use the alarm
attributes to process Fieldbus alarms.
Table 7.C ControlNet Discrete Input Object Attributes
Attribute
Number
Name Type Access Initial Value Remarks
3 Value Boolean Get 0
4 CNStatus Boolean Get Bad ControlNet status. 0-Good; 1-Bad.
150 Ffstatus uint8 Get Bad:Out of
Service
Fieldbus status of the value; obtained
from the Fieldbus device.
151 TagDesc String Get As configured Tag of the Fieldbus function block that is
represented by this object instance.
156 DiscAlmFlag uint8 Get/Set 0 See Alarm Handling for Discrete Inputs