InteliLite Global Guide
154
MODBUS
address
Meaning Access
MODICON object
type
MODBUS function
0000 .. 0999 Binary objects Read only Discrete Inputs Read: 01, 02
1000 .. 2999 Values Read only Input Registers Read: 03, 04
3000 .. 3999 Setpoints Read/Write Holding Registers
Read: 03, 04
Write: 06, 16
4200 .. 7167
Reserved
registers
Read/Write, depends on
each specific register
Input Registers
Holding Registers
Read: 03, 04
Write: 06, 16
Mapping data types to registers
As there are multiple data types in the controller but only one data type in MODBUS (the register, which is 2
byte long), a mapping table is necessary to compose and decompose the MODBUS messages correctly.
Data type Meaning
Number of
registers
Data maping
Integer8 1-byte signed integer 1
MSB = sign extension
LSB = value
Unsigned8 1-byte unsigned integer 1
MSB = 0
LSB = value
Integer16 2-byte signed integer 1
MSB = value, MSB
LSB = value, LSB
Unsigned16 2-byte unsigned integer 1
MSB = value, MSB
LSB = value, LSB
Integer32 4-byte signed integer 2
MSB1 = value, byte 3 (MSB)
LSB1 = value, byte 2
MSB2 = value, byte 1
LSB2 = value, byte 0 (LSB)
Unsigned32 4-byte unsigned integer 2
MSB1 = value, byte 3 (MSB)
LSB1 = value, byte 2
MSB2 = value, byte 1
LSB2 = value, byte 0 (LSB)
Binary8 8-bit binary value 1
MSB = 0
LSB = value, bits 0-7
Binary16 16-bit binary value 1
MSB = value, bits 8-15
LSB = value, bits 0-7
Binary32 32-bit binary value 2
MSB1 = value, bits 24-31
LSB1 = value, bits 16-23
MSB2 = value, bits 8-15
LSB2 = value, bits 0-7
Char 1-byte ASCII character 1 MSB = 0