Rockwell Automation 1788-CN2FF ControlNet-to-FOUNDATION Fieldbus H1 Linking Device User Manual - Manual (Page 27)

1788-6.5.1 - January 1999
Chapter
4
Using the ControlNet-to-FOUNDATION
Fieldbus H1 Linking Device
This chapter describes:
• the blocks in the linking device
• configuring the linking device to access the AI, AO, DI, DO function
blocks on the Fieldbus network from ControlNet
• attributes of the created ControlNet objects, assembly objects, alarm
handling
• ControlNet connection details
Blocks in the Linking Device The linking device is similar to an I/O subsystem. An I/O subsystem
typically contains several I/O modules. Each module has a number of
channels. The channels perform either analog input, analog output, discrete
input, or discrete output functions. The linking device models the I/O
modules in software. The linking device has four types of function blocks:
• Multiple Analog Input (MAI)
• Multiple Analog Output (MAO)
• Multiple Discrete Input (MDI)
• Multiple Discrete Output (MDO)
Each of these function blocks has eight channels. Each channel is a
combination of a value and Fieldbus status.
You can connect an analog input function block on the Fieldbus network to
a channel on the MAI block, just as you would wire a 4-20ma analog input
to an analog channel in your I/O subsystem. The main difference is that the
Fieldbus function blocks do considerable processing. The channel value
represents a scaled value in engineering units. Each value has an associated
status. The status is more than a boolean of good or bad. It has four major
status values of Good or Bad, with 16 sub-status values for each major
status, and four limits.