User Manual Owner's manual

Publication 1757-UM006A-EN-P - May 2002
7-4 Using the 1788-CN2FF, 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 7.A.
All attributes in Table 7.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
Table 7.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.