Midas
®
Gas Detector
A-3
Table A1 – User-Readable Modbus Holding Registers
Ref. Addr.
Reg. Name
Bits Function Value Enumeration
40001 STTS Status
nibble 0
0-3 Monitoring state integer
0: Warmup
1: Monitor mode with inhibit state “nonE”
2: Monitor mode but alarms inhibited, inhibit state “ALm”
3: Monitor mode but alarms and faults inhibited, inhibit state “AL-Ft”
4: Monitor mode but fully Inhibited, inhibit state “ALL”
5: Alarm / Fault Simulation
6: Bump test mode (largely same as state 2)
7: 4-20 mA loop Calibration mode
8: Calibration Mode other than state 7
9-15: for future expansion
nibble1
4-5 Fault status integer
0: No fault
1: Maintenance fault active
2: Instrument fault active
6 Alarm1 active
7 Alarm 2 active
nibble2
8 Relay 1 energized
9 Relay 2 energized
10 Relay 3 energized
11 Heartbeat Bit – toggles every two seconds to confirm communications
nibble3
12 Relays under remote Modbus/TCP control
13-15 for future expansion
40002 GASS Gas Selection
0-7 Gas ID
8-15 Sensor CartridgeID
40003 FCN1 Gas Concentration in floating point format word 1 of 2