User Manual Owner manual

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