Chapter 3 - Device Overview
76 3BHS335648 E82 UNITROL 1020 User Manual
configured between 1 and 247; the latter being the default value. A restriction applies
when the number is configured between 1 and 63 (except 32) and matches with the AVR
ID number for main channels or AVR ID number +32 for the redundant channel.
In these situations, the AVR will change the Remote Access Slave ID to 247 upon restart.
The Modbus Slave-ID for Remote Access can be configured between 64 and 247 without
restrictions. This is the range which is recommended for most applications.
The Modbus slave ID used for CMT1000 access is a number between 1 and 63, which
depends on the AVR-ID and the Channel Identification (Main or Redundant), even if the
Double Channel feature is not being used. When the parameterization is done using the
CMT1000, the Modbus ID used for CMT1000 is shown in the MODBUS Supervision
window. This number should not be used as Modbus Slave ID for Remote Access. For
further information refer to Chapter 6.4.7 Communication Menu.
3.4.7 Access Levels
Generally, digital inputs have the highest priority when controlling the AVR. Remote
access for control signals, e.g. Excitation ON, is only possible if the digital input is not
assigned.
The UN1020 device can be accessed from three different operators: Front Panel,
CMT1000 or Remote Access. While all operators can read data simultaneously, only one
of them can have control access and is allowed to write or change parameters in the
AVR. This concurrence is managed in the AVR main controller by assigning, to each
operator, a determined Access Level or privilege:
Local control mode (default)
The UN1020 device is by default in local control.
Front panel control (highest priority)
The customer can take over control to change parameters, the UN1020 device will
automatically switch back to local control mode
Customers who are taking control by the panel will block out other operators
CMT1000 control (medium priority)
CMT1000 can be connected to the target, where three different access levels are
defined: Offline, Monitor and Control.
If front panel control is granted, then CMT1000 cannot be set to control mode in
order to change parameters.
CMT1000 will block out other CMT1000 applications or remote access of plant
control system if CMT1000 control mode is used.
In case CMT1000 is disconnected from the target the UN1020 device will go back
to local control mode.
Remote access (lowest priority)
Remote access is granted only if the UN1020 device is in local control mode.
The Access Level status of each operator is stored in the AVR main controller and is
used to grant and deny access requests. An operator can request the change of its
Access level to the AVR main controller, i.e. from Monitor to Control. Access changes to
Monitor are normally granted without restrictions since all sources can read
simultaneously from the AVR.
An Access Level changing request can be denied when more than one CMT1000 and/or
more than one Remote Access device are trying to establish a connection to the same
AVR. The UN1020 supports a simultaneous connection of one CMT1000 and up to ten
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