Rockwell Automation 1756-LSC8XIB8I ControlLogix Low-speed Counter Module - Manual (Page 43)

Rockwell Automation Publication 1756-UM536A-EN-P - April 2012 43
Configure the Module Chapter 4
Direct 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.
One of the following occurs:
• 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 appears in the software. In this case, the configuration data
can be inappropriate for any of a number of reasons. For example, a
module’s configuration data may be appropriate except for a mismatch in
electronic keying that prevents normal operation.
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 faults in the data area associated with the
module. The RSLogix 5000 software may monitor this data area to signal the
module’s failures.
The time frame in which a module produces its data depends on the options
chosen during configuration and where in the control system the module
physically resides, such as locally or remotely.
Local Chassis Operation
A local chassis contains the module and its owner-controller. If a module resides
in a local chassis, the requested packet interval (RPI) instructs the module to send
its channel and status data to the local chassis backplane at specific time intervals.
IMPORTANT The RPI value is set during the initial module configuration by using
RSLogix 5000 software as described in
Configure Connection Properties on
page 48 . The RPI value can be adjusted when the controller is in Program
mode.
In addition to producing data at the RPI, the module also produces data when a
change in status occurs for the following input tags:
• Counter[x].InWindow0 or Counter[x].InWindow1—Indicates whether the
accumulated count or frequency value of Counter[x] is within the defined
window parameters.
• Pt[x].Data—Indicates the current On/Off value of the corresponding
hardware input.