Rockwell Automation 1756-LSC8XIB8I ControlLogix Low-speed Counter Module - Manual (Page 42)

42 Rockwell Automation Publication 1756-UM536A-EN-P - April 2012
Chapter 4 Configure the Module
Figure 14 - Module Communication with Owner-controller
A module’s communication, or multicasting, behavior varies depending upon
whether it operates in the local chassis or in a remote chassis.
Path No. Description
1 Controller transfers configuration data and commands to the module.
2 External devices generate input signals that are transmitted to the module.
3 Module converts signals, counts incoming pulses, calculates frequency and pulse width values, and then
stores the values.
4 Counter module transfers data, including accumulated count and frequency values, to the controller. The
controller stores the data in descriptive tags.
If configured, a 1756-OB16IEF peer module also consumes the data via a Listen-only connection to the
counter module. The peer output module evaluates the input data and applies the data to its outputs by
using program logic from the controller.
5 Program logic can store and move data before new input data is broadcast over the backplane and
overwrites the current input data in the controller’s tags. Program logic also updates values in output tags
that are sent to the counter module, such as preset and rollover values.
IMPORTANT: In RSLogix 5000 software, versions 18.02.00 and later, output tag information is sent to the
counter module only at the RPI rate defined during configuration. For optimal performance, use an
Immediate Output (IOT) instruction.
For example, the rung shown below contains an IOT instruction for a counter module in slot 3. Add a
similar rung to your last routine within the Main Task to mimic normal output tag processing.
ST
O
K
COUNTER
CTR
PEER DEVICE
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
Logix Controller Counter Module
1
2
3
4
5
Tags
Program Logic