Rockwell Automation 1756-CFM ControlLogix Configurable Flowmeter Module - Manual (Page 18)

18 Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
18 Configurable Flowmeter Operation in the ControlLogix System
1756-CFM modules follow these basic operational steps, as shown in Figure 2 .
1. The Logix controller establishes a connection to the CFM module and
downloads configuration via ladder logic and message instructions.
2. Flowmeters transmit input signals to the CFM module.
3. The 1756-CFM module calculates volume from accumulated pulse
counts as engineering units.
4. Rather than being scanned by an owner-controller, the 1756-CFM
module periodically multicasts its status to the controller. (see Requested
Packet Interval (RPI) on page 23 .) The 1756-CFM module also
multicasts its status to controllers connected by a listen-only connection
(
page 22 ).
5. The Logix owner-controller processes the data it received from the
1756-CFM module and returns the appropriate data.
Figure 2 - 1756-CFM Basic Operational Steps
IMPORTANT
A 1756-CFM module’s communication, or multicasting,
behavior varies depending upon whether it operates in the
local chassis or in a remote chassis. The following sections
detail the differences in data transfers between these
set-ups.
42732
Input
device
1
2
4
5 3
1756-CFM Logix controller