Rockwell Automation 1404-M4_M5_M6_M8 Powermonitor 3000 User Manual, PRIOR to Firmware rev. 3.0 - Manual (Page 87)

Publication 1404-UM001D-EN-E - October 2004
Communications 4-27
• 08 Diagnostics
– 00 Echo Command Data
– 02 Return Diagnostic Counters
– 10 Clear Diagnostic Counters
• 06 Write Single Holding Register
Function 06, 16 and the sub function 10 of function 08 support
Broadcast packets.
Refer to Appendix A for Modbus addresses of the Powermonitor 3000
data tables. The Powermonitor 3000 supports zero-based addressing.
The address ranges are arranged as follows (note that not all
addresses in the range are used):
• 30001 – 40000 Modbus Input Register (Analog Input) Address
Space
• 40001 – 50000 Modbus Holding Register (Analog Output)
Address Space
The Modbus protocol supports four types of data: Discrete Input, Coil,
Input Register and Holding Register. The Powermonitor 3000 supports
Input Registers (read-only) and Holding Registers (read-write or write
only).
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.
The Powermonitor 3000 return the Modbus error codes shown in the
table below when appropriate. In the event of an exception reply, not
only will the exception code be sent to the master device, but also the
Powermonitor 3000 slave’s diagnostic counter will record the error
code to further explain the error reason.
The data table number of error request and element offset of error
request in Table A.32 Write Error Status is updated with the first
Modbus address of the table and element offset that the incoming
request packet attempts to write to.