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Chapter 3: Operation within the System 15

1. Configure all I/O modules for a given controller using RSLogix 5000

and download that information to the controller.

2. If the I/O configuration data references a module in a remote chassis,

run RSNetWorx.

Important: RSNetWorx must be run whenever a new module is added

to a networked chassis. When a module is permanently removed from a

remote chassis, we recommend that RSNetWorx be run to optimize the

allocation of network bandwidth.

DirectDirect

Direct

ConnectionsConnections

Connections

A direct connection is a real-time data transfer link between the

controller and the device that occupies the slot that the configuration data

references. When module configuration data is downloaded to an owner-

controller, the controller attempts to establish a direct connection to each

of the modules referenced by the data.

If a controller has configuration data referencing a slot in the control

system, the controller periodically checks for the presence of a device

there. When a device’s presence is detected, the controller automatically

sends the configuration data. If the data is appropriate to the module

found in the slot, a connection is made and operation begins. If the

configuration data is not appropriate, the data is rejected and an error

message displays in the software. In this case, the configuration data can

be inappropriate for any of a number of reasons.

The controller maintains and monitors its connection with a module. Any

break in the connection, such as removal of the module from the chassis

while under power, causes the controller to set fault status bits in the data

area associated with the module. The RSLogix 5000 software may

monitor this data area to announce the modules’ failures.

Module OperationModule Operation

Module Operation

In traditional I/O systems, controllers poll input modules to obtain their

input status. Analog input modules in the ControlLogix system are not

polled by a controller once a connection is established. The modules

multicast their data periodically. Multicast frequency depends on the

options chosen during configuration and where in the control system that

input module physically resides. An input 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.

Modules in a Local

Chassis

When a module resides in the same chassis as the owner controller, the

following two configuration parameters will affect how and when the

input module multicasts data:

· Real Time Sample (RTS) configured via Real Time Sample tag.

· Requested Packet Interval (RPI) configured via I/O module properties.