Anybus X-gateway Module Description
1-2
© 2012 HMS Industrial Networks AB
Doc.Id. HMSI-168-25
Theory of Operation
The JMI provides centralized data storage, the “PassageWay
TM
”, for data that is
shared between the J1939 and Modbus networks. Data is placed into the Passage-
Way by one network interface, allowing the data to be read through the other net-
work interface.
The JMI appears as a single device on either network using standard protocol
mechanisms. No special, or extended, protocol features are required of the devices
on either network to read and write the data flowing through the PassageWay; all
cross-network activity is transparent to the devices on either network.
Figure 1-1 JMI PassageWay Operation
M
od
bus R
T
U Network
J1
93
9 Network
PassageWay
Input
Table
Output
Table
Receive PGNs
Send PGNs
Read Inputs
Write Outputs