DCP200 Profile Controller & Recorder -Product Manual
Page 78 Serial Communications 51-52-25-150, Issue 1 –April 2009
12 Serial Communications

Supported Protocols

Communication with a Modbus RTU or Modbus TCP master device is possible if the
appropriate communications module is fitted into Option Slot A. An RS485 Module is
required for Modbus RTU. An Ethernet Module is required for Modbus TCP.
The instrument can also act as Setpoint Master over RS485 in multi-zone applications. In this
mode the unit continuously sends its setpoint value using Modbus broadcast messages.
For a complete description of the Modbus protocol refer to the description provided at
http://www.modbus.org/
All models also have a configuration socket for use with the PC configuration software. An
RS232 to TTL lead (available from your supplier) is required in order to use this socket.
A front mounted USB port is available on some models; this can also be used to configure
the instrument or to transfer recorder or profile files via a USB memory stick.

RS485 Configuration

The RS485 address, bit rate and character format are configured via the front panel from the
Comms Configuration menu or by using the PC Configurator software.
Physical layer configuration settings possible are:
Data rate: 4800, 9600, 19200, 38400, 57600 or 115200 bps
Parity: None (default), Even, Odd
Character format: Always 8 bits per character.
Device Address: See below.

RS485 Device Addressing

The instrument must be assigned a unique device address in the range 1 to 255. This
address is used to recognise Modbus Queries intended for this instrument. With the
exception of globally addressed broadcast messages, the instrument ignores Modbus
Queries that do not match the address that has been assigned to it.
The instrument will accept broadcast messages (global queries) using device address 0 no
matter what device address is assigned. No response messages are returned for globally
addressed Queries.

Ethernet Configuration

For Modbus TCP communications (Modbus over Ethernet), the IP address can either be
assigned by a Dynamic Host Configuration Protocol (DHCP), BootP or AutoIP server on the
network, or manually assigned using the IP address allocation software tool.
Refer to the PC Software section of this manual for more information setting IP addresses.
The supported data rates 10/100BASE-T (10 or 100 Mbps) are automatically detected.