MSA Senscient ELDS 1000 series, Operating Manual

Page: 170 / 184

Appendix F – MODBUS Communications
170
Senscient ELDS™
Rev 15
GB
There are 5 single bit Coils (or bit input/output registers) as follows.
Coil Applies Content
1 Tx Implement Undisclosed Simu-Gas(with marker), Coil will return to zero
once Tx has completely finished the process. Note, following setting
the value subsequent reads will show the Coil value still at zero for
about 10 seconds. The value will be asserted once the SimuGas
process (timer driven in the Firmware) starts. The value then remains
asserted for about 1½ minutes whilst the Simu-Gas is operating
2 Tx Implement disclosed Simu-Gas (no marker), Coil will return to zero
once Tx has completely finished the process
3 Rx Assert Test values to 4-20mA outputs, must write zero back to this coil
to revert to gas monitoring.
NOTE : The controller must ensure that this value is written back to
zero as otherwise the ELDS Receiver will not be able to monitor gas.
The actual test current is specified by Holding register 7 (see below).
4 Rx L0 Zero Calibration, value will be reset to 0 once zero completed
5 Rx L1 Zero Calibration, value will be reset to 0 once zero completed
These are read/write bit data and can be read using the Modbus command 0x01 (Read Coils) and
can be written using commands 0x05 (Write Single Coil) or 0x0F (Write Multiple Coils).
Each of these registers are available on both ELDS Transmitter and Receiver units, however 1
and 2 only ‘apply’ to Transmitter units; whilst 3, 4 and 5 only ‘apply’ to Receiver units.
There are 41 Input Registers. These are all 16 bit (unsigned) quantities as follows:
Input Applies Content Comment
1 Rx L0 Gas Value, ppm
ppm.m
2 Rx L1 Gas Value, ppm
3 Tx & Rx L0 Full Scale Range
ppm.m
4 Tx & Rx L1 Full Scale Range
5 Tx & Rx Firmware Major Version
6 Tx & Rx Firmware Minor Version
7 Tx & Rx Firmware Build Version
8 Tx & Rx Unit Serial Number
Serial Numbers are Factory Set
9 Tx & Rx Paired Unit Serial Number
10 Rx L0, Last Simu-Gas Result
ppm.m
11 Rx L1, Last Simu-Gas Result
12 Rx L0 Signal ValueA
Signal = ValueA×ValueB/1000, units are
internal ELDS scale
13 Rx L0 Signal ValueB
14 Rx L1 Signal ValueA
15 Rx L1 Signal ValueB
16 Rx L0 Gas ValueA
Gas = ValueA×ValueB/1000, units are
ppm.m
17 Rx L0 Gas ValueB
18 Rx L1 Gas ValueA
19 Rx L1 Gas ValueB
20 Rx Last SG Year base 2000, so 2011 would be represented
by the year value 11