Allen-Bradley Powermonitor 3000 User Manual page 82

4-22 Communications
Publication 1404-UM001D-EN-E - October 2004
Indexed Reads of Large Data Structures
Large data structures that require indexed reads are most often read
into a computer-based application that performs further processing of
the data. The Powermonitor 3000 parses logs, oscillograms, harmonic
analysis results, setpoint status results, and other large data structures
into individual records to be read by the client and reassembled into
the original data structure.
You may select one of two modes for indexed table reads.
• Auto Increment - the Powermonitor 3000 automatically points to
the next record following each read of the specified results table
• Manual Increment - the client specifies a record to be read
during the next read of the results table by performing a write to
the applicable read-back select table.
Ethernet and DeviceNet communications options
IMPORTANT
support only manual increment mode.
The client selects the read-back mode by writing to the Read-back
Mode element in the appropriate read-back select table.
For native RS-485, optional RS-232 or optional Remote I/O, the
auto-increment mode provides the highest data throughput.
In manual increment mode, the client must alternate writes of the
read-back select table with reads of the read-back table. Figure 4.3
shows the flow of alternating writes and reads required for the manual
increment mode.
1. The client writes to the appropriate read-back select table to
identify the desired data block, record or channel. For selecting
a read-back record, the client may write either a valid password
or a value of -1 to the password element in the read-back select
table
2. After a short time delay, the client reads the results table, verifies
that it is the desired record and adds it into the target data
structure.
3. The client repeats steps 1 and 2 until all the desired data is read.