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10.2. Data and Control Flows in ETCS Modes
The transition matrix holds all transitions that are defined in the ETCS SRS for the subset
of modes and can be therefore easily compared with the transition table [88, p. 40] in the
specification document. It must be noted that only those conditions are part of the modelled
transition matrix that are applicable in ETCS Application Levels 0 and 1 because the selected
subset for the case study in Section 7.1 precludes Application Levels 2 and 3.
10.2. Data and Control Flows in ETCS Modes
In contrast to the gEVCStateMachine root graph, a gMainFunctionBlock is modelled for each
ETCS Application Level in each Mode. Thus, this section is divided in subsections for each
ETCS Mode and, where required, in sub-subsections for different Application Levels.
10.2.1. No Power Mode
Although the No Power Mode is not directly related to a certain Application Level, it is
relevant for the model that No Power is modelled for all possible Application Levels. Application
Level 0 is defined as default for No Power because it is the initial mode for a newly
started EVC binary. Anyway, it is possible that No Power is entered during the runtime
from another Mode in Application Level 1. For example, this is the case for the transition
Full Supervision c29−p2
−→ No Power.
Application Level 0
The main functionality in No Power is, according to [88, p. 10], the enforcing of the train stop
via the emergency brake system. Furthermore, the driver should be able to power up the
EVC (via the DMI), which should activate the transition “c4-p2” to the Stand By Mode. The
corresponding modelled data flow is sketched in Figure 10.2 as gMainFunctionBlock graph. Of
course, in a “real world” implementation of ETCS, powering the system refers to physically
powering, but since this case study is realised as pure software, this functionality bases on a
simple DMI input object.
The DMI is modelled by a separated oSubFunction object “DMI No Power” to be reusable in
other Application Levels. The corresponding model is shown in Figure 10.3. The DMI displays
the current ETCS Mode and Application Level to the driver. Additionally, the driver is able to
power up the system via the “System On Power” oDMIInput object.
Application Level 1
The only difference between Application Level 0 and 1 in the No Power mode is the assignment
of the “Stored ETCS Level” oVariableStorage object, which is therefore omitted. The DMI
is modelled by the same oSubFunction object as for Application Level 0 and was already
presented in Figure 10.3.
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