GASSONIC Observer-i - 6.0 Modbus Digital Interface; 6.1. Baud Rate; 6.2. Data Format; 6.3. Modbus Read Status Protocol (Query;Response)

GASSONIC OBSERVER-i
52
6.0 Modbus Digital Interface
The Gassonic Observer-i is available in a Dual Modbus configuration and in a Single Modbus + HART
configuration. For the Dual Modbus configuration, two independent Modbus communication channels
are provided and referred to as Comm 1 and Comm 2. For the Single Modbus + HART configuration,
the Modbus channel is referred to as Comm 1.
NOTE: The Dual Modbus configuration disables HART communication.
6.1. Baud Rate
The Baud Rate is a selectable setting via the Modbus communications interface. The selectable baud
rates are 57600, 38400, 19200, 9600, 4800, or 2400 bps.
6.2. Data Format
The Data Format is a selectable setting via the Modbus communications interface. The selectable data
formats are as follows:
Data Bits Parity Stop Bit Format
8 None 1 8-N-1
8 Even 1 8-E-1
8 Odd 1 8-O-1
8 None 2 8-N-2
Table 5: Data Format
6.3. Modbus Read Status Protocol (Query/Response)
6.3.1. Modbus Read Query Message
Byte Modbus Range
Referenced to Gassonic Observer-i
1
st
Slave
Address
1-247 * Gassonic Observer-i ID (Address)
(X = 0 or 1 Model Type)
2
nd
Function
Code
03 Read Holding Registers
3
rd
Starting
Address Hi**
00 Not Used by Gassonic Observer-i
4
th
Starting
Address Lo**
00-FF (Hex) Gassonic Observer-i Commands
5
th
No. of
Registers Hi
00 Not Used by Gassonic Observer-i
6
th
No. of
Registers Lo
01 No. of 16 Bit Registers
7
th
CRC Lo 00-FF (Hex) CRC Lo Byte
8
th
CRC Hi 00-FF (Hex) CRC Hi Byte
Table 6: Modbus Query Messages
NOTE*: Address 0 is reserved for broadcast mode and is not be supported at this time.
NOTE**: Start Address can be a maximum of 247 Address Locations (0000-0x00F7).