905U-G Wireless Gateway
User Manual
Page 127
©September 2004
Finally, it must be taken into consideration that the 905G Modbus Plus module dynamically
adjusts the 4X register range available to the network depending on the fieldbus mappings
configured. The 905G will terminate the available 4X register range at the last mapped 4X
register for both the read and write area. In the example above this means that the only 4X
registers that are available to the Modbus Plus network are 40001 – 40048 and 41025 –
41072.
NOTE – considering this constraint, it is still strongly advised to use fieldbus interface
registers always starting at the lowest addressed locations, thus limiting unnecessary
processing overhead on the 905G.