We have with us UPS system which supports J-bus protocol. Earlier intigrator was on Modbus protocol. Is it necessary that the address of the parameter should be same? Is J-bus and Modbus communication possible?

Please help me as early as possible...

 

My understanding is that J-Bus and Modbus has the same set of function codes and frame formats, hence it is interoperable. There is one register shift in J-Bus addressing which needs to be take care while communicating with modbus.

Jose Thomas,
Kalki Communication Technologies Limited
E-mail: [email protected]
Web: http://www.kalkitech.com
Phone : (+91) (80) 2572 1263 / 1264 / 5501 / 5498
: (+91) (80) 4110 8310 / 8362
Fax : 91-80-2572 5473

 

Modbus and J-Bus are the same except for the register/coil address. In "true" Modbus, the address of the "first" register or coil is specified as "1" and in the actual message sent on the wire it is decremented by one so to read the "first" register or coil the actual message on the wire has a register/coil number of 0.

In J-Bus communication, the number of the "first" register/coil is also specified as "1" but this number is not decremented in the message on the wire so it will appear as number 1.

Many devices offer configuration selections that will compensate for this addressing problem.

Jerry Miille