Installation guide
192 Message Routing
890 USE 100 00
B .2 Modbus Address Conversion
Modbus devices use addresses of one byte in the range 1 ... 255.
Modbus Plus nodes are addressed in the range 1 ... 64, with five bytes
of routing imbedded in each Modbus Plus message.
Modbus messages received at the Modbus port of a programmable
controller in bridge mode must be converted to the fivebyte routing
path used on Modbus Plus. Modbus messages received at a Bridge
Multiplexer Modbus port must also be converted.
The Modbus address in the message determines the final routing over
Modbus Plus. Figure 74 compares the methods used by programmable
controllers in bridge mode and Bridge Multiplexers for converting
Modbus addresses.
Programmable controllers convert the address using the methods
shown in Figure 74. Bridge Multiplexers first compare the address to
an internal table of Modbus Plus paths, using routing from the table if
a match is found. If a match is not found in the table, the methods
shown in Figure 74 are used.