USSI Microlok II Functional description
UM-6800A Rev1.3 July 2005 Page 21 of 27
8.1. SYSTEM OPERATING MODES
The Microlok II controller is a complex combination of hardware and
software. when the system can not function in the Normal Operating Mode.
Other system modes must be supported to allow access to those system
functions that are still operational even though the entire system is not
functional at that time.
Critical Errors in the Microlok II system may be caused by persistent or
transient faults. After a Critical Error has occurred, the Microlok II will be
reset and will perform complete system diagnostics.
The most common persistent Critical Errors are related to vital physical
output processing. In order to attempt to provide some system functions in
the presence of persistent Critical Errors, the unit will discontinue the vital
physical output functions and, if there are no other Critical Errors
encountered, continue to run in a downgraded mode. If Critical Errors
continue to occur, all system application processing will be discontinued.
The Microlok II system will be capable of operating in seven different modes.
8.1.1. NORMAL MODE
In this mode, all outputs and application processing are active. All other
system functions are available at user request. This will be the default mode
for systems operations in the absence persistent of Critical Errors.
8.1.2. SELECTIVE SHUTDOWN MODE
This mode will be entered when persistent Critical Errors prohibit complete
system operations. In this error mode, all of the Vital Physical Outputs will
be disabled. In this mode, other application processing, such as logic
processing, Serial Links, Vital Physical Inputs and Non-Vital I/O continues.
8.1.3. USER SELECTIVE SHUTDOWN MODE
In this mode all Vital Physical Outputs are disabled. This mode will be
entered when identified as the operational mode by the Application Logic and
the unit would otherwise operate in the Normal Mode as identified above. In
this mode, other application processing, such as logic processing, Serial
Links, Vital Physical Inputs and Non-Vital I/O continues.
8.1.4. COMPLETE SHUTDOWN MODE
In this mode, no system I/O or logic processing will be performed and all vital
outputs will be in the most restrictive state. This mode will be entered when
persistent Critical Errors prohibit system operations. When possible,
Diagnostic Interfaces will function.
