Rockwell Automation 1788-CN2FF ControlNet-to-FOUNDATION Fieldbus H1 Linking Device User Manual - Manual (Page 36)

1788-6.5.1 - January 1999
4-10 Using the 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 4.C.
All attributes in Table 4.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.
Each attribute corresponding to a process alarm has the three alarm-related
bits as shown in Figure 4.8.
Table 4.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