Detcon TP-700 - Program Features; Operational Features

Model TP-700
TP-700 Instruction Manual Rev. 4.1 Page 27 of 42
4. RS-485 Modbus™ Protocol
Model DM-700 sensors feature Modbus™ compatible communications protocol and are addressable via the
program mode. Other protocols are available. Contact the Detcon factory for specific protocol requirements.
Communication is two wire, half duplex 485, 9600 baud, 8 data bits, 1 stop bit, no parity, with the sensor set up
as a slave device. A master controller up to 4000 feet away can theoretically poll up to 256 different sensors.
This number may not be realistic in harsh environments where noise and/or wiring conditions would make it
impractical to place so many devices on the same pair of wires. If a multi-point system is being utilized, each
sensor should be set for a different address. Typical address settings are: 01, 02, 03, 04, 05, 06, 07, 08, 09, 0A,
0B, 0C, 0D, 0E, 0F, 10, 11…etc.
Sensor RS-485 ID numbers are factory default to 01. These can be changed in the field via the Operator Interface
described in Section 3.5.5 Set Serial ID.
The following section explains the details of the Modbus™ protocol that the DM-700 sensor supports.
Code 03 - Read Holding Registers is the only code supported by the transmitter. Each transmitter contains 6
holding registers which reflect its current status.
Table 3 Modbus™ Registers
FC
REG
Content Description
R/W
Content Definition
Value
Meaning
Range
03
40000
Device Type
R
8
700 Sensor
03
06
40001
40001
Read Detectable
Range
1,2
Write Detectable Range
R/W
100
10000
For 0-100
For 0-10000
2
DM – 0 to 10000
FP – Read only
TP – 20, 50, 100, 200
IR – 0 to 10000
PI – 0 to 10000
03
40002
Read Concentration
3,2
R
1000
Bound by range. If > range, this
value is in fault.
03
06
40003
40003
Read AutoSpan Level
4,2
Write AutoSpan Level
R/W
50
Span gas at 50
DM – 1% to 95% of Range (40001)
FP – 5% to 95% of Range (40001)
TP – 2% to 50% of Range (40001)
IR – 5% to 95% of Range (40001)
PI – 1% to 95% of Range (40001)
03
40004
Read Sensor Life
R
85
For 85% sensor life
03
40005
Read Fault Status Bits
5
R
0x0001
0x0002
0x0004
0x0008
0x0010
0x0020
0x0040
0x0080
0x0100
0x0200
0x0400
0x0800
0x1000
0x2000
0x4000
0x8000
Global Fault
Auto Span Fault
Temperature Fault
4-20mA Fault
Input Voltage Fault
Memory Fault
Processor Fault
Clearing Fault
Stability Fault
Range Fault
Sensor Fault
Zero Fault
Sensor Fault 2
<reserved>
In Calibration
Communication Error
03
40006
Read Model #
R
1, 2, 3, 4, 5
DM, FP, IR, TP, PID
respectively
03
40007
Read Days Since Cal
R
29
29days
03
40008
4-20 Current Output
mA x100
R
400
4.00mA
Range
03
40009
Read Input Voltage
V x100
R
2400
24.00V
03
40010
Read Temperature
R
28
28 °C
03/
06
40011
Special #1
R/W
Function dependent on value of
40006 (See Special Register
Table 4)