
Main Menu
Serial Port S1/S2
Communications
Revision 9
900 Control Station User Guide
25
May 2014
Table 8 Serial Port S1/S2 Settings (right side of display)
Setting
Description
Protocol
ELN: The default protocol, used to communicate with the HC Designer
configuration software.
MODBUS MASTER: The controller acts as a Modbus Master device on the
communication link.
MB MASTER ADVANCED: The controller acts as a Modbus Master device on the
communication link. This protocol provides enhanced data throughput for
applications where the HC900 is being used with a “Modbus-to-fieldbus” gateway
device.
MODBUS SLAVE MULTI: The controller acts as a Modbus Slave device. This
protocol allows more than one slave device to be present on the communications
link (multi-drop).
MODBUS SLAVE PTP: The controller acts as a Modbus Slave device. This
protocol can be used if the controller is the only slave device on the link (Point-to-
point).
MODBUS SLAVE MODEM: The controller acts as a Modbus Slave device. This
protocol provides the extended delays that are needed to access the controller via
a modem.
Baud Rate (Bps)
Select 9600, 19200, 38400, 57600 or 115200 bits per second.
Modbus Parity
Select None, Odd, or Even parity.
Modbus Stop Bits
Select 1 or 2 Stop Bits.
Slave Address (1-247 or
255)
This is the address of the controller on the Modbus link when one of the three
Modbus Slave protocols is selected. All devices on the link must have a unique
Modbus address. The address may be set to a value of 1 to 247, or it may be set
to 255. A value of 255 disables the port for this controller.
Slave Port Enable
This item allows you to enable or disable the port:
ENABLE: The port will respond to communication requests.
DISABLE: The port will ignore communication requests.
Double Register Format
Under the Modbus protocol, each IEEE 32-bit floating-point number requires two
consecutive Modbus registers, for a total of four bytes. The stuffing order of the
bytes within these registers differs among Modbus devices. To provide
compatibility with the various hosts, the double-register format is configurable. The
selections are:
FP B Big Endian format Byte order: 4, 3, 2, 1
FP L Little Endian format Byte order: 1, 2, 3, 4
FP BB Big Endian with byte-swap Byte order: 3, 4, 1, 2
FP LB Little Endian with byte-swap Byte order: 2, 1, 4, 3