Introduction 
14    HC900 Process & Safety Controller User and Installation Manual  Revision 6 
    21 April 2017 
 
  Ethernet 10/100 Base-T connection:  
 Port(s) configured to Auto Negotiate - default to half duplex 
  C30/C30S controller up to 5 PC hosts via Modbus/TCP protocol. C50/C50S, C70/C70S and 
C70R Legacy and C75/C75S (new model) support up to 10 PC hosts via Modbus/TCP protocol.  
 Peer-to Peer (UDP) communication with up to 32 other HC900 Controllers. 
 C70/C70S and C70R Legacy and C75/C75S (new model) have 2 Ethernet ports for connection to 
up to 10 PC hosts. They also support Modbus/TCP Initiator function over both ports and 
automatically switch between ports to maintain Peer to Peer communications with other 
C70/C70S or C70R/C75/C75S redundant CPUs. 
  Private Ethernet 100 base T connection to I/O expansion racks: (except C30 and C30S CPU) 
 Direct connection to each C70R Legacy and C75/C75S (new model) CPU. 
For more information 
For complete feature summary and specifications see Specifications on page 206.