Bulletin No. 3020IM9503R6/98 Power Meter
December 1998 Chapter 6—Communications
1998 Square D All Rights Reserved 39
MODBUS RTU PROTOCOL
Alternately, power meters can communicate using the Modbus RTU protocol.
Using 4-wire Modbus, you can daisychain up to 32 power meters to a single
communications port. When using 2-wire Modbus communications, a
maximum of 16 power meters can be daisychained to a single communication
port.
Note: See Appendix H for 2-wire Modbus wiring and distance limits.
A power meter Modbus communications link can be connected to a commu-
nications port on any of the following:
• personal computer
• Modicon programmable controller
• other host devices with a Modbus-compatible port
JBUS PROTOCOL
Jbus is the third protocol by which power meters can communicate. When
using 4-wire Jbus, up to 32 power meters can be daisychained from a single
communications port. For 2-wire Jbus, a maximum of 16 power meters can be
daisychained.
Note: See Appendix H for 2-wire Jbus wiring and distance limits.
You can connect a power meter Jbus communications link to any host device
with a Jbus-compatible port.
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