Agrowtek RD8i, Instruction Manual, Page: 13 / 14

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13
Data registers are 16 bits wide with addresses using the standard MODICON protocol. Floating point values
use the standard IEEE 32-bit format occupying two contiguous 16 bit registers. ASCII values are stored with
two characters (bytes) per register in hexadecimal format. Coil registers are single bit values which control
and indicate the status of a relay; 1 = on, 0 = off.
Register Types
Supported Commands
MODBUS Holding Registers
Parameter Description Range Type Access Address
Address Device Slave Address 1 - 247 8 bit R/W 40001
Serial# Device Serial Number ASCII 8 char R 40004
DOM Date of Manufacture ASCII 8 char R 40008
HW Version Hardware Version ASCII 8 char R 40012
FW Version Firmware Version ASCII 8 char R 40016
Timeout (seconds) Turn off relays if no communication 0 - 32767 16 bit, unsigned R/W 41001
Relay Closure Count
Relay 1
Unsigned Int 32 bit, unsigned R
49001
Relay 2 49003
Relay 3 49005
Relay 4 49007
Relay 5 49009
Relay 6 49011
Relay 7 49013
Relay 8 49015
MODBUS Coil Registers
Parameter Access Address
Relay 1 R/W 1
Relay 2 R/W 2
Relay 3 R/W 3
Relay 4 R/W 4
Relay 5 R/W 5
Relay 6 R/W 6
Relay 7 R/W 7
Relay 8 R/W 8
0x01 Read Coils
0x03 Read Multiple Registers
0x05 Write Single Coil
0x06 Write Single Register
0x15 Write Multiple Coils
A request to use a function that is not available will return an illegal function error (0x01).
A request to read or write a register that is not available will return an illegal address error (0x02).
A request to read or write coils that are not available will return an illegal address error (0x02.)