Allen-Bradley Powermonitor 3000 User Manual page 90

4-30 Communications
Publication 1404-UM001D-EN-E - October 2004
DeviceNet Communications Option
The Powermonitor 3000 with optional DeviceNet communications
operates as a slave device on a DeviceNet network. It will serve data
to a DeviceNet master station such as a PLC-5 or SLC 500 DeviceNet
scanner, a ControlLogix DeviceNet bridge module, a PanelView
operator terminal and RSLinx direct and pass-thru DeviceNet drivers.
It supports I/O (implicit) Messaging, Explicit Server Messaging and the
explicit Unconnected Message Manager (UCMM) as discussed below.
I/O Messaging
The Powermonitor 3000 supports polled, change-of-state and cyclic
I/O messaging using assembly instances 1 for input data and 2 for
output data. The default input messaging table size is 6 integer
elements and the output table size is 2 integer elements. This
corresponds to a DeviceNet scanner mapping of 12 Rx and 4 Tx bytes.
See Table A.2 on page A-4 for the contents of the default I/O
messaging tables.
You may reconfigure the input messaging table
TIP
(instance 1) by selecting up to 23 integer or 14
floating-point parameters through a table write to
assembly instance 35. Refer to User-configured I/O
on page 4-54. If you change the size of the input
table, you must also re-map the inputs into the
DeviceNet scanner using RSNetworx for DeviceNet.
Polled I/O messaging can automatically provide fresh data at update
rates as fast as 100 mS. The Powermonitor 3000 supports both Every
Scan and Background polled messaging. You select the poll type and
polling rate using RSNetworx for DeviceNet software.
• Every Scan: Polls the Powermonitor 3000 once per scan. Set the
Interscan Delay to at least 100 mS. An Interscan Delay of less
than 100 mS will slow the Powermonitor 3000's delivery of
metering information.
• Background: Polls the Powermonitor 3000 at intervals you
specify using the Foreground to Background Poll Ratio. So long
as the Powermonitor 3000 is polled no more frequently than
every 100 mS, it will operate and communicate at its optimal
rate. You may calculate the total scan time with this formula: