AMC-DTM-Sensor Transmitter
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Appendix A - Modbus Accessible Data
The Modbus functions that are supported are:
1 – Read coil
3 – Read Holding Registers
6 – Write Single Register
16 – Write Multiple Registers
Modbus Accessible features
Data
Modbus
Register #
or Coil #
Modbus
function
Read/Write
Access
Alarm 1 status (LSB bit 0,1&2: 0-off, 1-on, 2-
Activation Delay timer active, 3-Silence timer
active, 4-Run Timer active)
1 3 R
Alarm 2 status (LSB bit 0,1&2: 0-off, 1-on, 2-
Activation Delay timer active, 3-Silence timer
active, 4-Run Timer active)
2 3 R
Alarm 3 status (LSB bit 0,1&2: 0-off, 1-on, 2-
Activation Delay timer active, 3-Silence timer
active, 4-Run Timer active)
3 3 R
Fail Alarm status (LSB bit 0-off, 1-on)
4
3
R
Alarm 1 type (LSB bits 0&1: 0-disabled, 1-
increasing, 2-decreasing)
5 3/16/6
RW
Alarm 2 type (LSB bits 0&1: 0-disabled, 1-
increasing, 2-decreasing)
6 3/16/6
RW
Alarm 3 type (LSB bits 0&1: 0-disabled, 1-
increasing, 2-decreasing)
7 3/16/6
RW
Alarm 1 threshold *
8
3/16/6
RW
Alarm 2 threshold *
9
3/16/6
RW
Alarm 3 threshold *
10
3/16/6
RW
Alarm 1 silence timer value (0-99 minutes)
11
3/16/6
RW
Alarm 2 silence timer value (0-99 minutes)
12
3/16/6
RW
Alarm 3 silence timer value (0-99 minutes)
13
3/16/6
RW
Engineering units (ppm:0, ppb:1, %LEL:2,
%VOL:3)
14 3
R
Current gas concentration * **
15
3
R
Range *
16
3/16/6
RW
Zero Buffer (in % * 10 (9.9% written as 99)
17
3/16/6
RW
Test (when LSB bit is 1 test is running. When
it is 0, test is not running)
18 3/16/6
W
Reserved 19
3
R
Gas label (Each register contains 2
characters. Register 20 contains MSByte,
register 15 LSByte)
20-25 3
R
Alarm 1 status Coil (0-alarm is off or alarm is
in Activation Delay state. 1-alarm is on,
Silence timer is active or Run Timer is active)
Coil 1
1
R
