RLE LD5200 V.2.3 - Manual (Page 89)

rletech.com LD5200 User Guide 89
5 Modbus Communication
5.4.2 Function 04: Read Input Registers
To read the LD5200 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).
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 5.4 Read Input Registers Packet Structure