Honeywell High VoltageTerminal Block (Euro style) Note 3 900TER-0101
Use of properly configured managed switch is recommended to mitigate potential cyber-security/DOS
problems. Safety applications must include a properly configured Firewall. See Ethernet Devices/
Considerations on page Error! Bookmark not defined. for suggested settings.
Redundant Networks
Honeywell Matrikon OPC Server supports redundant networks. Up to 10 connections may be distributed in
any combination across the controller’s 2 network ports (E1 and E2). PC hosts may include, for example,
HMI supervisory software and/or Designer Software configuration software. Redundant ports may be used
in a simplex mode (non-redundant).
Peer-to-Peer Communication
Peer-to-peer communication enables any given HC900 Controller to request a peer relationship with up to
32 other HC900 Controllers on the same subnet; other controllers can request a peer relationship with the
controller. The total number of peers that a controller can have a relationship with is 32. Peer-to-peer
communication uses the Ethernet Open Connectivity network and employs standard User Datagram
Protocol (UDP) for fast and efficient transfer of information. Peer-to-peer communication is based on failsafe
and data expiration mechanisms that provide for fault and loading considerations without requiring
reserved network bandwidth allocation. Peer-to-peer is designed to be easy to configure as part of a
device’s standard configuration and does not require the distribution of a global database.
With redundant controllers, peer-to-peer communication always stays with the Lead controller.
Implementing peer-to-peer communications involves:
Interconnecting controllers with Ethernet media and networking devices (cables, switches, etc)
Configuration (via Designer Software):
Controller configuration, which includes entry of an IP address and a Subnet Mask, and a Controller
Name for each controller. (The Controller Name is used only by the Honeywell proprietary
software for network access between controllers; it should not be confused with a Network Domain
Name or Workgroup Name.)
Peer Data Exchange (PDE) function blocks, which are included in the control strategy (configuration
file). PDE function blocks include PDE Control, PDE Write, and PDE Read. (Refer to the HC900
Process Controller Function Block User Guide for additional information.)
Safety Peer function blocks, which are included in control strategy (configuration file). Safety Peer
function blocks include Safety Peer Monitor, Safety Analog Import and Safety Digital Import.
Applicable for Safety controllers with version 6.300 and above
An illustration of HC900 Controller Peer-to-Peer on a Local Area Network (LAN) is given in Figure 19.
Typically, a Router is used for interconnection to another network (LAN, WAN, or other). However, Peer
controllers must all be on the same subnet.
For additional details, refer to the HC900 Process & Safety Controller Safety Manual.

Figure 19 – Modular Network Structure
Connection to PC Hosts
For legacy systems, connection to PC hosts (for example, PCs that include HMI supervisory software
and/or Designer Software configuration software) can be via Modbus/TCP as well as serial Modbus RTU
over either the RS-485 or RS-232 communications ports. Both ports support Modbus RTU and are
configurable as master or slave.
For new systems, connection to PC hosts can be via Modbus/TCP as well as serial Modbus RTU over the
galvanically isolated RS-485 communication ports.
The TCP hosts can be concurrent with Modbus hosts on one or both of the other ports. Any given
controller is capable of concurrent communication with up to 5 TCP hosts on C30/C30S controllers or up to
10 TCP hosts on C50/C50S, C70/C70S or C75/C75S controllers. (The meaning of the term “host” varies,
but for this definition, a PC host is any PC that is on the same LAN as the controller, or on any LAN or
WAN (Wide Area Network) that is network-connected to the controller.
Each HC900 Controller has 5 or 10 “sockets” (software and memory resources), each of which can service
data requests from any networked PC on a client (host)/server (controller) basis. The sockets are available
on a first-come, first-served basis. Typically, when the data service for any PC Host request is completed
or times out, it allows the socket to become available to any other PC Host in the hierarchy of networks.
Note: PDE communications, discussed previously, do not use the PC host connection sockets. PDE
communications are separate from (and are transmitted concurrent with) PC host-to-controller
communications
The PC host can include software that closely relates to and supports controller functioning and can also
include other software that is related remotely or not at all. Closely related software can include:
Either
Designer Software – for generating and managing configuration files, Or
HMI (Supervisory/Data Acquisition Software) or Operator Panel with Modbus/TCP driverOr
Both configuration and HMI software (and or panel)
All communications between a controller and a PC host use Open Modbus/TCP protocol, whose
widespread use is making it an industry standard. Modbus/TCP is basically an adaptation of the Modbus
messaging structure that uses TCP/IP for a message carrier. In general, Modbus messaging is available
in two versions: ASCII, in which each eight-bit byte is sent as 2 ASCII characters, and RTU, in which
each byte is sent as two four-bit hexadecimal characters. Each Modbus message frame is embedded into
a TCP/IP datagram as indicated in Figure 20.
Figure 20 – Modbus/TCP Framing
The HC900 Controller uses either Modbus/TCP or Modbus RTU, not ASCII. The “fixed” Modbus
mapping structure for the HC900 Controller is based on the mapping structure employed in Honeywell’s
UMC800 Controller, and the function codes and methods for parameter access are also virtually
identical. Modbus Maps
In your controller’s configuration certain parameters are each automatically assigned a Modbus address.
These include certain types of function blocks (such as loops and set point programmers), signals and
variables, among other items. Through their addresses these parameters can be accessed or displayed
remotely, such as by a third-party operator interface. Collectively, these Modbus addresses and
parameters are known as the Modbus map.
Two Modbus Mapping options exist: Fixed map and Custom map
Using HC Designer, you can use a pre-defined fixed map where common parameters are mapped out
automatically at fixed addresses, or you can configure a custom map for configurations rev. 4.0 or
higher.
Function blocks added to the controller in release 4.0 and higher are not automatically included in the
Fixed Modbus Map. To access the registers of these function blocks, the Custom Modbus Map must
be used and the block data manually inserted into the custom Modbus map.
HMI Supervisory/SCADA software is available from various suppliers, and functionality and setup
requirements vary with suppliers and with specific products. In all cases, the software selected must be
compatible with Open Modbus/TCP protocol.