A.8 Access control
Access control manages whether the Modbus master is allowed to modify device parameters.
Reading of parameters is always possible. The general access control rules are:
● The Modbus interface has an access level that can be changed by providing PIN information
via the Modbus register 8292 (User PIN) or 8293 (Expert PIN).
● The default fieldbus access level can be set using Modbus register 6348, with the following
possible values:
– 32: End User Privilege
– 16: Restricted User Privilege
● Each parameter has a protection level assigned that specifies the required access level to
modify the parameter via the Modbus interface.
● If the access level of the Modbus interface is lower than the protection level of the parameter
that is desired to be modified, then the attempt to modify the parameter is rejected by the
device.
If the device is defined as a custody transfer (CT) device and the CT write protection DIP switch
is ON (locked), the device will deny all writes to CT parameters independent of the access
control.
Table A-7 Access control
Access level Description
Read only The Modbus master is not able to modify the device configuration (setup parameters).
The Modbus master is only able to execute the command, to reset PINs.
This is the default level of the Modbus interface.
User The Modbus master has to provide the correct user PIN with Modbus register 8292 to reach this access
level.
The Modbus master is able to modify a subset of the device configuration.
Expert The Modbus master has to provide the correct expert PIN with Modbus register 8293 to reach this access
level. The Modbus master is able to modify the configuration of the device.
If an incorrect user PIN or an incorrect expert PIN is entered, or if the device does not receive
any request within 10 minutes, the device resets the access level to read only.
A.9 Modbus holding registers tables
In the following the Modbus RTU holding registers available for SITRANS FS430 are
described.
Note
All Write parameters require password access.
Modbus communication
A.9 Modbus holding registers tables
SITRANS FST030 (Modbus)
140 Operating Instructions, 08/2018, A5E37367739-AD
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