Rockwell Automation 1408-EMxx PowerMonitor 1000 Unit - Manual (Page 50)

50 Rockwell Automation Publication 1408-UM001D-EN-P - September 2013
Chapter 3 PowerMonitor 1000 Memory Organization
Data Table Access Controllers and client applications may read or write single element, multiple
elements or complete tables as permitted by the addressing selected.
Each data table’s read/write access is listed in Appendix A .
The power monitor requires a valid password before it accepts a write. There are
two ways a password may be written.
• An entire table including a valid password may be written.
• A valid password may be written to the Single element password write
table which then enables single element writes until 30 minutes without a
single element write elapses.
Data Table Data Format The power monitor stores data in two basic formats.
• Integer, in which the 16-bit word may be represented by a signed integer
value or a bit field
• Floating-point, in the 32-bit IEEE 754 format
Modbus input registers and holding registers are 16 bits long. Floating point
values in the data tables are represented as big-Endian two-register arrays in
IEEE-754 floating point format. The Modbus client application must be able to
reassemble the two-word array into a valid floating-point value.
An example Modbus address for a floating-point value is 40101-2. Register
40101 holds the most significant bytes of the number and 40102 holds the lowest
significant bytes.