Chapter 3 - Device Overview
UNITROL 1020 User Manual 3BHS335648 E82 77
independent Remote Access connections per device (maximum). If those limitations are
surpassed, one or all connected operators can lose their access and go Offline. This
practice is not recommended by ABB. The method to change Access Levels from Panel,
CMT1000 and Remote Access is explained in the following sections. For more details
about UN1020 user interfaces, refer to Chapter 6 - Operation.
3.4.7.1 Panel
The Panel is normally in Monitor mode. By clicking the LOC button, the access right is
given to the panel. All other operators are blocked out.
3.4.7.2 CMT1000
The CMT1000 manages the Access changing requests (Offline, Monitor and Control) by
using a graphic slide-bar displayed in the software main window. The slide-bar shows the
CMT1000 current access status from the AVR and allows the user to simply change it by
sliding up and down. For more information about the user interfaces see Chapter 6 -
Operation.
Changing to Control mode is not granted if the panel is in local mode. If the Plant control
system is in Control mode over remote access, the CMT1000 forces it into Monitor mode.
This means the plant control system has only read access.
Offline or disconnected (no access)
If the status of an operator is Offline, the AVR microcontroller considers the
operator as not connected to the UN1020 and, therefore, there is mainly no data
exchange with the AVR. Only when using the CMT1000 as operator and the
presence of a compatible AVR is detected, a small quantity of data is exchanged to
provide and display the AVR-ID information on the main window of the software.
Monitor (read access)
If an operator has Monitor Access, it is only possible to read data from the device
(i.e. measurements, parameters, etc.). Data cannot be changed or modified in the
AVR during this access mode. All the operators, i.e. Panel, CMT1000 and Remote
Access, can have Monitor access to the AVR at the same time; all of them can read
simultaneously from the same AVR.
Control (read and write, full access)
If an operator has Control Access, he has full control of the device (write and read
data). All operators can request Control Access, but the access will be granted to
only one operator at the same time, based on the operator's priority.
3.4.7.3 Remote Access
Changing of Access Levels from Remote Access is performed by requests via Modbus
protocol. Control access level is only granted if no other operator is in control mode. For
more information, refer to the UN1020 Modbus Reference document: Doc. No
3BHS358281 E80.
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