Rockwell Automation 1756-HSC ControlLogix High Speed Counter Module - Manual (Page 58)

Rockwell Automation Publication 1756-UM007C-EN-P - November 2011
58 Configure the 1756-HSC Module
The timing of this ‘reserved’ spot may not coincide with the exact value of the
RPI, but the control system guarantees that the owner-controller receives data
at least as often as the specified RPI. As shown in the illustration, data from
the remote chassis is sent to the ControlNet bridge module at a rate no slower
than the configured RPI.
Data from Remote Chassis Sent to ControlNet Bridge Module
You must run RSNetWorx software to enable 1756-HSC modules in a remote
ControlNet (networked) chassis. Running RSNetWorx software transfers
configuration data to networked modules and establishes a network update
time (NUT) for the ControlNet network that is compliant with the desired
communication options specified for each module during configuration.
If you are not using 1756-HSC modules in a networked ControlNet chassis,
running RSNetWorx software is not necessary. However, anytime a controller
references a 1756-HSC module in a networked chassis, RSNetWorx software
must be run to configure the ControlNet network.
In an Ethernet network with a multicast connection, a module sends new data
when prior data has not been transferred for one-quarter of the RPI. For
example, if data is being sent every 10 ms and the RPI is set at 100 ms, the data
transfer rate is every 30 ms.
ControlNet Network
Data sent at the RPI rates
HSC module
Local Chassis Remote Chassis
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