Chapter 5 - Connection to a controller
Version EN-092019-1.21
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5
Connection to a controller
The following chapter describes how to establish a Modbus connection using the engineering systems
Schneider Unity Pro and Siemens TIA Portal.
5.1
Modbus Mapping
The Modbus Gateway maps the statuses of the PROFIBUS masters and the PROFIBUS slaves to a number
of Modbus registers. In addition, the gateway offers a register-based command interface for acyclic
reading and writing of PROFIBUS device parameters.
Select
MODBUS TCP Mapping
.
5.1.1
Master status
The operation mode of the PROFIBUS master can be read and changed in the low bytes of Modbus
registers 8500, 8628, 8756 and 8884.The following diagram shows the Modbus registers used for the
segments of different Modbus Gateway .
Register
mbGate PA – 4 CH
mbGate PA - 2 CH
mbGate PB
mbGate DP
8500
Status PA-0
Status PA-0
Status PA-0
Status DP-0
8628
Status PA-1
Status PA-1
Status PA-1
-
8756
Status PA-2
-
Status DP-0
-
8884
Status PA-3
-
-
-
When a PROFIBUS master is started it takes on the operation mode
Stop
. In this mode, PROFIBUS input
data is read but no output data is written to the PROFIBUS slaves. If you want the PROFIBUS master to
write output data to the PROFIBUS slaves, you must set the master to operation mode
Run
by writing
value 3 to the corresponding Modbus holding register.
