Rockwell Automation PLC-5 Fieldbus Solutions for Integrated Architecture User Manual - Manual (Page 60)

Publication 1757-UM006A-EN-P - May 2002
2-16 Integrating Fieldbus into Rockwell Automation Logix System
Fieldbus Discrete Output data manipulation
When the DO[n] from the Device Control (DEVCTL) function block is
wired to the CAS_IN_D input for a fieldbus Discrete Output function
block, the Control Builder automatically creates a CEE output agent to
handle the discrete output to the fieldbus block. The block-like output
agent maps the ProcessLogix DO[n] with status parameter to the
fieldbus data structure (DS-66) of the CAS_IN_D parameter. It
interprets the value portion in ProcessLogix terms and converts it to
fieldbus representation.
The CEE output agent also accepts a single BKCAL_OUT_D parameter
with the fieldbus data structure (DS-66) and maps it to the
BACKCALIN parameter of the DEVCTL block in ProcessLogix terms.
It sends the outgoing “control signal” either to a subscribed parameter
or a client/server written parameter through the CAS_IN_D or
RCAS_OUT_D connection. It can optionally receive the
backcalculation signal from either the corresponding published
parameter or client/server read parameter.
The ProcessLogix data quality is converted to fieldbus data quality.
The ProcessLogix Good indication is represented as fieldbus
Good(Cascade).
The ProcessLogix control initialization indicators map only to the
limited number of substatus conditions that have corresponding
indications in fieldbus Good(Cascade).
Interface Connections Summary
Since the downstream action with the upstream feedback is the same
for all fieldbus blocks, there are essentially the following six types of
interface connections through the FIM.
• Analog process value into the FIM.
• Discrete process value into the FIM.
• Analog process output from the FIM.
• Discrete process output from the FIM.
• Analog process output from the FIM with backcalculation
feedback.