B&B Electronics MODSCAN32 - Manual - Manual (Page 20)

20
READ INPUT REGISTERS (FUNCTION CODE 04)
Function Code 04 obtains the contents of the controllers input registers. These locations receive their vales
from devices connected to the I/O structure and can only be referenced, not altered from within the
controller nor via MODBUS.
The example below requests the contents of register 30009 in slave number 17.
ADDR
FUNC DATA
START
PT HO DATA
START
PT LO DATA #
OF REGS
HO DATA #
OF REGS
LO ERROR
CHECK
FIELD
11 04 00 08 00 01 E2
In the response message, the contents of register 30009 is decimal value 0.
ADDR
FUNC BYTE
COUNT DATA
INPUT
REG HO
30009 DATA
INPUT
REG LO
30009 ERROR
CHECK
FIELD
11 04 02 00 00 E9