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Appendix A: Modbus Communications User Guide: LDRA6

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A-2.2 Read Input Registers

To read the LDRA6 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

Table 3: Read Input Registers Packet Structure

Read Registers Request Packet Read Registers Response Packet

Slave Address (1 byte) Slave Address (1 byte)

04 (Function code) (1Byte) 04 (Function code) (1 byte)

Start Register *2 bytes) Byte count (1 byte)

# of register to read (2 bytes) First register (2 bytes)

Crc Checksum (2 bytes) Second register (2 bytes)

…

Crc Checksum (2 bytes)

Table 4: Input Registers

30001 Status Bit Level Status (see Table 5) None 0-65535

30002 Leak Current Zone 1 Leakage current on cable uAmps 0-65535

30003 Leak Current Zone 2 Leakage current on cable uAmps 0-65535

30004 Leak Current Zone 3 Leakage current on cable uAmps 0-65535

30005 Leak Current Zone 4 Leakage current on cable uAmps 0-65535

30006 Leak Current Zone 5 Leakage current on cable uAmps 0-65535

30007 Leak Current Zone 6 Leakage current on cable uAmps 0-65535

30008 Input Selection Bit Level Status (see Table 6) None 0-65535

30009 Reserved

30010 Version Firmware version xx.xx X 100 0-65535

Table 5: Status Flags (Register 30001)

Bit Read Registers Response Packet

00 1 = Zone 1: Leak is Detected / Contact Closure Alarm

01 1 = Zone 2: Leak is Detected / Contact Closure Alarm

02 1 = Zone 3: Leak is Detected / Contact Closure Alarm

03 1 = Zone 4: Leak is Detected / Contact Closure Alarm

04 1 = Zone 5: Leak is Detected / Contact Closure Alarm

05 1 = Zone 6: Leak is Detected / Contact Closure Alarm

06 0

07 0

08 1 = Zone 1 Cable Break Alarm

09 1 = Zone 2 Cable Break Alarm

10 1 = Zone 3 Cable Break Alarm

11 1 = Zone 4 Cable Break Alarm

12 1 = Zone 5 Cable Break Alarm

13 1 = Zone 6 Cable Break Alarm

14 0

15 0