128    HC900 Process & Safety Controller User and Installation Manual  Revision 6 
    21 April 2017 
Set IP addresses and 
subnet masks. 
C30/C50: 192.168.1.254 and Subnet Mask of 255.255.255.0. 
C70/C75: E1: 192.168.1.254, E2: 192.168.2.254. Must be on 
different subnets. 
Links to controller communication ports 
Refer to Table 17 and the figure in Step 2 above. Port availability depends on Controller model. 
 
Table 17 – Links to Controller Communication Ports 
Controller 
Port 
/Connector Type 
Legacy controller 
only RS-232 
3-plug connector 
RS-232 Null Modem 
cable, up to 50’ 
Or 
RS-232 PC modem 
cable, up to 50’ 
Serial port of PC (w/ Null 
Modem cable)  
or  
Modem.  Refer to RS-
232 Remote Connection 
to PC Configuration Tool 
on page 135. 
For Wiring details of 
Null Modem cable see 
Table 19. 
Legacy controller 
only RS-232 
3-plug connector 
Modbus master 
(controller is single 
slave) 
RS-232 Null Modem 
cable, up to 50’ 
Or 
RS-232 PC modem 
cable, up to 50’ 
RS-232 to RS-485 
converter 
Refer to device’s port 
instructions 
Legacy controller 
only RS-232 
3-plug connector 
Modbus master 
(controller is one of 
multiple slaves) 
RS-232 to RS-485 
converter 
Refer to device’s port 
instructions 
Legacy controller 
only RS-232 
3-plug connector 
Modbus slave 
network (controller 
is master) 
RS-232 to RS-485 
converter 
Refer to device’s port 
instructions 
Belden #9271 (or 
equivalent) 
Terminal connector of 
operator interface. (Refer 
to Table 18.) 
Connect from each CPU 
(A and B) to the OI.  
SIL applications require 
shield drain wire to be 
connected to grounding 
bar. 
Modbus master 
(controller is slave) 
Belden #9271 (or 
equivalent) 
Refer to device’s port 
instructions 
SIL applications require 
shield drain wire to be 
connected to grounding 
bar. 
Modbus slave 
network (controller 
is master) 
Belden #9271 (or 
equivalent) 
Refer to device’s port 
instructions 
SIL applications require 
shield drain wire to be 
connected to grounding 
bar.