Serial Ports; Figure 25 - Controller Serial Ports - Honeywell HC900 User And Installation Manual

Serial Ports

(RS-232 and RS-485 for legacy systems and two galvanically isolated RS-485 ports for new
systems)
Overview

For Legacy systems, the S1 default setting is RS-232; S2 default setting is RS-485. Each port can be set
to RS-232 or RS-485 (see page 43). For RS-232 cable connections see page 134. For RS-485
connections see page 152.

For new systems, either of two ports S1 and S2 can be configured as RS-485. For SIL applications
communication cable shield connection must be made to IO grounding bar instead of the connector
shield connector.

Ports configurable as ELN (default) or Modbus RTU.

Controller can act as Modbus master or slave through either port.

Controller can be slave to masters such as

On Legacy systems- Operator Interface (1040, 559). Must be on galvanically isolated RS-485 port S2.

Honeywell HC Designer PC software

Third party PC HMI software

Third party Operator Interface

Controller can be master to slaves such as

Any Honeywell Modbus device (e.g., recorders, controllers, flame safety)

Any non-Honeywell Modbus device.
Only one master port at a time; can't have both serial ports as master ports.


Modbus master ports default to slave ports, ELN protocol when CPUs are in Program mode.

Baud rates to 115,200
42
Figure 22 – Controller Serial Ports
HC900 Process & Safety Controller User and Installation Manual Revision 6
21 April 2017