Modbus Communication Interface; Baud Rate; Data Format; Unit Address - MSA Ultima OPIR-5 Programming Manual

1. Modbus Communication Interface

Modbus is a standard RS-485-based protocol used for serial communication with the Ultima OPIR-
5 Detector. The Ultima OPIR-5 Detector has a two-channel Modbus (or single Modbus and single
HART) compatible interface for communication with the control room equipment such as
programmable logic controllers (PLCs).
By default from the factory, Ultima OPIR-5 Detector Modbus interface is set at the baud rate of
9600 bits per second, data format of 8-N-1, and with a unit address of 1 on the serial channel CH1
and 2 - on the serial channel CH2. These settings can be configured through the display user
interface by navigating to the relevant setup ("SE") menu items using an MSA magnet.
The communication defaults can also be restored at any time by connecting the RESET (brown)
wire to the power supply common, and, subsequently, turning on the power to the Ultima OPIR-5
Detector. Ten seconds after the power-up, the RESET wire should be disconnected from the power
supply to prevent a wire shortage fault.

1.1 Baud Rate

The baud rate is a selectable parameter on the Ultima OPIR-5 Detector Modbus communication
interface. The available baud rate settings of 2400, 4800, 9600, 19200 and 38400 bits per seconds
can be selected and configured via either Ultima OPIR-5 Detector display or Modbus interface.

1.2 Data Format

The data format is a selectable setting via the Ultima OPIR-5 Detector Modbus communication
interface. The selectable data formats are as follows:

1.3 Unit Address

Every Ultima OPIR-5 Detector unit with a Modbus capability has a unit address assigned to it for
communication. The available Modbus unit addresses for external communication can range
between 1 and 247.
Ultima OPIR-5 Modbus Programming Guide
Table 1: Data Format
Data Bits Parity
8 None
8 Even
8 Odd
8 None
5
Stop Bit Format
1 8-N-1
1 8-E-1
1 8-O-1
2 8-N-2