7 modbus equivalent addresses, Chapter 2 – installation, Power leader™ ethernet gateway – GE GEH6505A User Manual

Page 11: 2–7 modbus equivalent addresses

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POWER LEADER™ Ethernet Gateway

Chapter 2 – Installation


manual) to record the devices attached to each

network and verify that each device on each

network has a unique address.

3. Modbus Concentrators may be used to add

POWER LEADER commnet devices to a

Modbus network. The Concentrator assigns a

Modbus-equivalent address to each commnet

device attached to it. See Section 2-7 for a

discussion of commnet and Modbus-equivalent


NOTE: While Modbus Concentrators are counted

as regular Modbus devices, the commnet devices

attached to Modbus Concentrators do NOT count

toward the 31 device/network limit, but ARE

considered in the 247 address/network limit.

4. No connections between Modbus networks are

permitted, either directly or through repeaters.

5. Modbus networks are constrained to a

maximum 4,000 feet of communication cable

without repeaters.

6. RS485 repeaters may be used to extend the

wiring length of a Modbus network or to

provide isolation between runs of cable in a

Modbus network. Refer to GEH-6502 for

appropriate wiring lengths with repeaters.

2–7 Modbus Equivalent Addresses

A maximum of 31 Modbus devices can be

supported on a single RS485 network of the

Ethernet Gateway. However, the Modbus RTU

protocol permits up to 247 individual addresses to

be recognized. These additional 216 addresses may

be utilized by commnet devices attached to a special

Modbus device, the Modbus Concentrator.
Commnet is a communications protocol utilized by

many of the devices from GE’s POWER LEADER

family of power management devices. The Modbus

Concentrator is a Modbus RTU device that permits

commnet devices to be assigned Modbus-equivalent

addresses. Each Modbus Concentrator keeps track

of up to 32 commnet devices and directs traffic

between the Modbus network and the commnet

devices. To the Modbus network, the commnet

devices appear as valid Modbus addresses.
To provide seamless integration of commnet-

compatible devices into the Modbus RTU network,

the Concentrator directly maps commnet addresses

to equivalent Modbus addresses. The valid range of

commnet addresses recognized by the concentrator

is 300–514. These addresses are one-to-one mapped

to the equivalent Modbus address range of 33–247.
For a more detailed discussion of commnet devices

and the function of the Modbus Concentrator, see

GEH-6491, the Modbus Concentrator Users Guide.
Table 4 lists commnet devices supported by the

Modbus Concentrator (and the Ethernet Gateway).




Full-function, three-phase electronic
meter with optional pulse initiation;
simple retrofit to existing
electromechanical installations. See
GEH–6302 for a full description.

POWER LEADER Meter Full-function three-phase meter with

optional protective relaying and
waveform capture. See GEH–5892.

Overcurrent Relay

Three-phase and ground protection
against overloads and rapid
detection of short circuits.
See GEK–100682.

Spectra ECM™

Advanced motor protection in full-
voltage-nonreversing (FVNR) and
full-voltage-reversing (FVR)
combination starter applications.
See GEH–6435.

MicroVersaTrip PM™ trip
unit in Spectra RMS™
molded-case circuit

Overcurrent protection and optional
full-function metering and protective
relaying. See GEH–5934.

MicroVersaTrip PM™ trip
unit in AKR, Power
Break® and Power
Break® II insulated-case
circuit breakers.

Overcurrent protection and optional
full-function metering and protective
relaying. See GEH–6273.

Table 4. POWER LEADER commnet devices supported by the

Modbus Concentrator.