Rockwell Automation PLC-5 Fieldbus Solutions for Integrated Architecture User Manual - Manual (Page 174)

Publication 1757-UM006A-EN-P - May 2002
7-14 Using the 1788-CN2FF, ControlNet-to-FOUNDATION Fieldbus H1 Linking Device
Alarm Handling by the
HMI The linking device makes the process alarms from AI and DI function
blocks visible as attributes of the created ControlNet objects, as
discussed in the previous sections. Fieldbus devices generate other
types of alarms; for example, they send out an alarm whenever their
static configuration changes. Other function block types also generate
alarms. In general all alarms, except the AI and DI process alarms,
must be handled by a Fieldbus HMI. You must configure the linking
device to receive such alarms and forward them to a PC-based HMI
on ControlNet. You set up the linking device as shown in Figure 7.9.
Figure 7.9 Setting Up an Alarm
If you connect the AI and DI alarms to the linking device, the linking
device forwards all alarms from these to the HMI. The process alarms
are also visible to your PLC processor through the ControlNet objects.
You must ensure, through your application design, that either the HMI
or the PLC processor acknowledges the process alarms.
Assembly Objects For each channel that you connect on the MAI, MAO, MDI, and MDO
blocks, the linking device creates an instance of a ControlNet object
corresponding to the type of channel. These individual instances are
useful for unscheduled querying and setting object information. For
scheduled communications on ControlNet, the linking device takes
specific attributes from the corresponding object instances and
combines them into input and output assembly objects.
The linking device uses input assembly objects to produce data on
ControlNet and output assembly objects to consume data from
ControlNet. The definition of assembly objects is determined after you
configure the MAI, MAO, MDI and MDO blocks on the linking device.
Assembly offsets are 0 based and increment by the size of data placed
into them.