Rockwell Automation 1788-CN2FF ControlNet-to-FOUNDATION Fieldbus H1 Linking Device User Manual - Manual (Page 30)

1788-6.5.1 - January 1999
4-4 Using the ControlNet-to-FOUNDATION Fieldbus H1 Linking Device
ControlNet Analog Input Objects
The linking device creates an instance of a ControlNet AI object for every
wired channel in the MAI block instances. Each instance of the ControlNet
AI object has the attributes and access rules shown in Table 4.A.
All attributes in Table 4.A are created if a standard Fieldbus AI function
block is connected to a channel of an MAI block. Otherwise, only Value,
CNStatus, TagDesc, and FFstatus are created.
Alarm Handling for Analog Inputs
You can configure Fieldbus AI function blocks to detect and report alarms.
Four process alarms (HI_HI_ALM, HI_ALM, LO_LO_ALM, and
LO_ALM) are exposed through the ControlNet AI object. When you
connect an AI function block to an MAI block, the NI-FBUS Configurator
configures the field device to send the four alarms 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 4.3.
Table 4.A ControlNet Analog Input Object Attributes
Attribute
Number Name Type Access Initial Value Remarks
3 Value Float Get 0
4 CNStatus Boolean Get Bad ControlNet status. 0-Good; 1-Bad.
107 LoFlag uint8 Get/Set 0 See Alarm Handling for Analog Inputs
108 HiFlag uint8 Get/Set 0 See Alarm Handling for Analog Inputs
109 LoLoFlag uint8 Get/Set 0 See Alarm Handling for Analog Inputs
110 HiHiFlag uint8 Get/Set 0 See Alarm Handling for Analog Inputs
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.