Eaton Power Xpert PXM 4000, User And Installation Manual

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IM02601004E
Page 185
A MODBUS Communication
A MODBUS COMMUNICATION
A.1. Modbus Register Mapping
The Power Xpert Meter platform supports many standard buffers; however, it has extend-
ed functionality such that complete new sets of registers are required.
A.2. Register 2001 (Invalid Object Access Configuration)
Register number 2001 is used to configure the product to respond to a group of data ob -
jects, of which some objects are invalid within that group.
When set to zero (default), the product will respond to a group of objects with data
contained in the valid objects of the group along with 0000
16
data contained in the in-
valid objects (or an invalid number, if available: for example floating point value NaN =
7FF20000
16
). This allows access to a block of registers using a single read command, of
which some are not implemented in that block, rather than multiple read commands, which
contain only implemented registers. The application is thus responsible for selecting the
implemented registers. The starting register number must be a valid object. If the starting
register number accesses an invalid object, the illegal data object exception code 02 will
be issued, regardless of this configuration setting.
When set to non zero, any attempt to access a group of data objects, which contain an
invalid object will result in an illegal data object exception code 02.
A.3. Register 2002 (Floating-Point Data Register Configuration)
Register number 2002 is used to configure the 32 bit IEEE floating point word order.
When set to zero (default), the floating point high-order 16 bit word is placed first in the
Modbus register (x) followed by the low order 16 bit word in the next Modbus register
space (x+1). The resulting transmission order is 3
rd
byte, 2
nd
byte, 1
st
byte and lastly 0
th
byte, with bit 24 transmitted first.
When non zero, the floating-point low order 16 bit word is first in the Modbus register
space.
A.4. Register 2003 (Fixed-Point Data Multi-Register Configuration)
Register number 2003 is used to configure the 32 bit and 64 bit fixed point word order
(including the 64 bit extended energy objects).
When set to zero (default), the fixed point multi-register high order 16 bit word is placed
first in the Modbus register (x) followed by the next lower order 16 bit word in the next
Modbus register space (x+1) and so forth. For 32 bit objects the resulting transmission
order is 3
rd
byte, 2
nd
byte, 1
st
byte and lastly 0
th
byte, with bit 24 transmitted first. For 64 bit
objects the resulting transmission order is 7
th
byte, 6
th
byte, 5
th
byte, 4
th
byte, 3
rd
byte, 2
nd
byte, 1
st
byte and lastly 0
th
byte, with bit 56 transmitted first.
When non zero, the fixed-point low order 16 bit word is first in the Modbus register space.