Hardware reference guide

Ethernet Modules
332
35013379 02 October 2007
Key Features of
Global Data
The main features for Global Data are:
z One Publisher and many Subscribers
z A device can publish one network variable of up to 512 registers
z A device can subscribe to several network variables of up to 2048 4x registers
z A device subscribes to the complete network variable
z One distribution group per network IP address
z Application defined publication rate
z Up to 64 Global Data network variables (numbered from 1 to 64) can be part of
the data distribution group
z An NOE has only one multicast address; consequently, it can only publish and
subscribe inside the group
z A device can participate in several distribution groups by using multiple NOEs in
the rack
Global Data has an advantage over Client/Server services when more than one
Subscriber is receiving the same data since only one transaction is necessary for all
Subscribers to receive the data.
This advantage offers two benefits:
z Reduce overall network traffic
z Ensure tighter synchronization of multiple subscribers
Bandwith
Monitoring
Bandwidth Monitoring allows you to monitor the NOE’s CPU allocation for each of
the following services: Global Data, I/O Scanning, and Messaging. The Bandwidth
Monitoring service retrieves workload data and returns one of two pieces of
information: whether the module has free resources or whether the module is
working at capacity. Knowing the resource allocation helps you:
z Decide about allocating your resources
z Determine the number of NOEs needed in a system
Available
Services
The services accessed and monitored are:
z Global Data
z I/O Scanner
z Modbus Messaging
If you use Bandwidth Monitoring, you do not need to develop a new set of access
functions. The actual NOE CPU load is computed each second.
Bandwidth
Monitoring Load
Rates
The Bandwidth Monitoring service checks once a second and computes four (4)
values in private data:
z Percentage of NOE’s CPU allocated to Global Data
z Percentage of NOE’s CPU allocated to the I/O Scanner
z Percentage of NOE’s CPU allocated to Messaging
z Percentage of NOE’s CPU allocated to other services and idle
This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com