Chapter 3
Start-up and Operation
RS-485 Output
The Gasgard 8 Controller uses an RS-485 serial interface with
Modbus protocol. To communicate to the RS-485 output via a
computer interface, an isolated RS-485 converter should be used.
The baud rate is 1200 or 9600 baud with RTU format sent. Each
byte has eight bits with no parity and two stop bits.
Table 3-1. Channel Card Register Addresses
TITLE
REGISTER
ADDRESS
CHANNEL
NUMBER
FORMAT
Gas Concentration
40001
1
0 to 1000 (full-scale)
40002
2
40003
3
40004
4
40005
5
40006
6
40007
7
40008
8
Alarm State
40009
1
See TABLE 3-2
40010
2
40011
3
40012
4
40013
5
40014
6
40015
7
40016
8
Table 3-2. Alarm State Format
BIT 5 TO
BIT 15
BIT 4
BIT 3
BIT 2
BIT 1
BIT 1
Free
Fault
Alarm 4
Alarm 3
Alarm 2
Alarm 1
Chapter 3, Start-up and Operation
3-1
