Softing Modbus mbGate PA User Manual page 34

Modbus Gateways - User Guide
Acyclic writing
The controller initiates acyclic PROFIBUS writing by writing a specific command to the control registers of
the command interface and writing the data to the data registers. The last data register to be written
depends on the length of the data and is calculated as base register + 5 + (data length / 2). It is important
that command and the data are written by consistent multiple register access.
Register
base register + 0
base register + 1
base register + 2
base register + 3
base register + 4
base register + 5
Basisregister + 6
Basisregister + 7
...
The first, third, fifth, ... byte must be in the high byte of the register while the second, fourth, sixth, ... byte
must be in the low byte of the register.
The gateway responds immediately to the writing access. Depending on whether the values in the control
registers are valid, writing access is granted or refused.
34
Value
3
station address of the PROFIBUS device
slot number within the device
parameter index within the slot
Number of bytes of data to be written. The maximum value is 246.
first and second byte of data to be written
third and fourth byte of data to be written
fifth and sixth byte of data to be written
Version EN-092019-1.21