Rockwell Automation 1756-XXXX ControlLogix Analog I/O Modules - Manual (Page 31)

Publication 1756-UM009C-EN-P - December 2010 31
Analog I/O Operation in the ControlLogix System Chapter 2
Worst Case RPI Scenario
In the worst case scenario, the controller sends the data just after the ‘reserved’
network slot has passed. In this case, the module does not receive the data
until the next scheduled network slot.
Remote Output Modules Connected Via the EtherNet/IP Network
When remote analog output modules are connected to the owner-controller
via an EtherNet/IP network, the controller multicasts data in the
following ways:
• At the RPI, the owner-controller multicasts data within its own chassis.
• When the RPI timer expires or a programmed Immediate Output (IOT)
instruction is executed. An IOT sends data immediately and resets the
RPI timer.
IMPORTANT
These best and worst case scenarios indicate the time required
for output data to transfer from the controller to the module
once the controller has produced it.
The scenarios do not take into account when the module will
receive new data (updated by the user program) from the
controller. That is a function of the length of the user program
and its asynchronous relationship with the RPI.