TELEDYNE OLDHAM SIMTRONICS iTRANS 2 - 6.2 Modbus Register List

iTRANS 2
FIXED POINT SINGLE OR DUAL GAS MONITOR
WITH DUAL ANALOG OUTPUTS
USER MANUAL
36
77036429-EN
Revision 7.0
IMPORTANT: When commissioning master and slave units on a ModBus network, it is critical to
ensure that every device on the ModBus network must have a unique address. Otherwise,
abnormal behavior of the entire serial bus can occur.
6.2 Sample Gas Reading via ModBus Network
To get a gas reading for Channel 1, you must read register 40102. This register holds the gas
reading in ppm.
• Example: Gas reading of 5 ppm = register value of $0005.
• Example: Gas reading of 20.9% = register value of $0209.
For Channel 2 you can access the gas reading by looking at register 40202.
For a full list of ModBus commands and registers that are accessible on the , refer to the
next section.
6.3 ModBus Register List
ModBus register addresses are provided in Table 6-1.
Addr
Inst
R/W
Host
R/W
Range
Description
40101 R/W R/W
MSB = $01 to
$FF
LSB = $01 to $F7
Sensor Type
Holds the sensor instrument type code and ModBus address. The most significant
byte (MSB) holds a value indicating the type of instrument (see below). The least
significant byte (LSB) holds a value which is the ModBus address of the sensor.
MSB = Instrument type code $01 to $FF
$03 = IR (infrared)
$04 = TOX (toxic)
$05 = OXY (oxygen)
$06 = AAW (toxic)
$07 = CAT (catalytic)
LSB = MODBUS sensor address $01 to $F7 (1 to 247)
40102 W R $0000 to $FFFF
Gas Reading
Holds the gas reading in ppm or percent depending upon the sensor in the
instrument. The range is from $0000 to $FFFF and represents a signed decimal value
range from -32768 to +32767.
Examples:
+5 ppm = register value of 00005
10
= $0005
-5 ppm = register value of 65531
10
= $FFFB
40103 R* R*
MSB = $01 to
$FF
LSB = $01 to $FF
Gas Type
Holds the decimal place holder and the gas type code. The most significant byte
(MSB) holds the number of decimal places to be used in calculations for this gas. This
decimal locator applies to all subsequent values of gas readings within other
registers. This can be read by the instrument. The least significant byte (LSB) holds a
code which identifies the gas type. This can be read by the host.
MSB = Decimal place holder $01 to $FF
LSB = Gas type code $01 to $FF
$01 CO Carbon Monoxide
$02 H
2
S Hydrogen Sulfide
$03 SO
2
Sulfur Dioxide
$04 NO
2
Nitrogen Dioxide
$05 Cl
2
Chlorine