JBus dan ModBus

I saw that you have a TOP Server Driver for the Modbus protocol, will this support JBus as well? If yes; Is there anything I should be aware of when configuring this in TOP Server?

The Modbus Protocol was initially developed by Modicon. April develeoped their own version of Modbus; later dubbed JBus. The two protocols are certainly compatible, and the TOP Server Modbus driver will be able to communicate with devices that speak either protocol.

There are a few considerations that need to be taken into account:

1. Modbus is natively a 0 based addressing protocol (Reg+1), whereas JBus is natively a 1 based addressing protocol (Reg+0). The register offset of 1 can easily be configured in the device properties "Use zero based addressing" found under the Settings tab
2. Modbus and JBus have different "limitations" when it comes to packet capacity

	JBus	Modbus
Number of Stations on bus	255	247
Max number of bits to be read in single request	2000	1920
Max number of words to be read in single request	125	120
Max number of bits to be writen in single request	1968	1920
Max number of words to be written in single request	123	120

This limitation must be taken into account when setting up the Block Settings of the TOP Server device - since Modbus is lower across the board there should not be any problems with JBus Devices.

If communicating with a JBus device and experiencing problems, please contact our technical support staff and we would be more than happy to assist