RLE LD1500 V.3.1 - Manual (Page 40)

40 LD1500 User Guide 800.518.1519
5 Modbus Communication
5.2.2 Function 04: Read Input Registers
To read the LD1500 input values, the master must send a Read Input Registers request packet.
The Read Input Registers request packet specifies a start register and the number of registers
to read. The start register is numbered from zero (30001 = zero, 30002 = one, etc).
Table 5.4 Read Input Registers Packet Structure
Read Registers Request Packet Read Registers Response Packet
Slave Address (1 byte) Slave Address (1 byte)
04 (Function code) (1 byte) 04 (Function code) (1 byte)
Start Register (2 bytes) Byte count (1 byte)
# of registers to read (2 bytes) First register (2 bytes)
CRC Checksum (2 bytes) Second register (2 bytes)
…
CRC Checksum (2 bytes)
Table 5.5 Input Registers
Register Name Description Units Range
30001 Status Bit Level Status None 0-65535
30002 Leak Distance Location of Leak Ft/Meters 0-65535
30003 Units Unit of Measure 1=Ft 0=Meters 0-65535
30004 Leak Current Leakage current on cable μ Amps 0-65535
30005 Cable Length Installed Cable Length Ft/Meters 0-65535
30006 Loop1 Res Resistance of cable Ohms 0-65535
30007 Loop2 Res Resistance of cable Ohms 0-65535
30008 Res/Ft Resistance of cable Ohms x1000 0-65535
30009 Version Firmware version xx.xx X 100 0-65535
Table 5.6 Status Flags (Register 30001)
Bit Description
00 1 = Leak is Detected
01 1 = Cable Break Alarm
02 1 = Contamination is detected
03 1 = Summary Alarm
04-15 Spare