Honeywell HC900 User Manual page 11

The Transaction Identifiers and Protocol Identifiers in the header are normally all 0's (4 bytes total) while the Length
field identifies the number of bytes in the Modbus frame. The controller will transmit the correct number of bytes for
the remainder of the frame. However, the controller does not check this field for messages received.
The standard IEEE 32-bit floating point and 16-bit integer formats are used.
Parameter Addressing
The definition in Table 6-1 is the fixed map overview listing starting and ending addresses.
Greater detail for parameter addressing relating to a particular function class (e.g, loops, setpoint programmer, signal
tags) is in referenced sub-sections. Function Codes 1, 2, 3, 4, 5, 6, 8, 16 (10h), and 17 (11h) are supported (see
Table 4-1 Modbus/TCP and Modbus RTU Function Codes Definitions).
Examples for read or write access to parameters supported by the various function codes are provided in Sections 4.3
through 4.11.
Reference
The Open Modbus/TCP Specification can be obtained at the Modicon website:
http://www.modicon.com/openmbus/standards/openmbus.htm
HC900 Ethernet Communications Setup
See the HC900 Process Control (HC) Designer Users Guide, Doc. # 51-52-25-110 or respective HC Designer Help
Files for setting up the following network parameters:
IP Address, Subnet Mask (optional), Default Gateway IP Address (optional)
1. Be sure the PC, HMI panel, or other Host device has a Network Interface Card (NIC) with an IP
address (fixed or DHCP served) that allows access to controllers on the same or other subnet. Consult
your IT department or network administrator for allocating IP addresses to the controllers as required.
2. You will need to set each controller's IP address prior to network connection since every HC900
controller is shipped with the default IP address of 192.168.1.254. Placing multiple controllers on the
same network before they have been given unique IP addresses will cause problems.
3. On the PC, use the Utilities Worksheet in the HC Designer software to set up the serial RS-232
connection to the controller at the desired baud rate. This will require a null modem cable.
4. Select the Set Controller's Network Parameters button. Using the wizard (bottom radio button), select
the PC COM port to be used, then set the controller's new network parameters including IP address,
Subnet Mask (if other than default, 255.255.255.0), and Default Gateway IP address (if required,
otherwise leave at default 0.0.0.0). See your IT network administrator for proper entries. (Refer to the
on-line help provided with the HC Designer software, Utilities Worksheet, Set Controller's Network
Parameters, for further details on this step).
Note: This setup will require the controller to be placed temporarily in the Program mode. After the new
network parameters have been downloaded, the controller will conduct a Cold Start in its transition to RUN.
This will cause an initialization if there is a current configuration in the controller.
The fixed IP address of each controller shall be set independently prior to placing on the network. See your IT
systems administrator for allocating IP addresses, subnet masks, or default gateway IP address as necessary (network
address filtering and routing may be necessary if the controller network access will not to be confined locally within
the plant environment).
Revision 13
April 2017
HC900 Process Controller Communications User Guide
Introduction
Modbus/TCP Interface
3