Short Description
Timebase has been introduced to cope with the need of modeling, various temporal referential used in an automotive distributed systems design (clocks from different ECUs, motor position, etc).
TADL2 timing expressions contain explicit TimeBase which represents a discrete and totally ordered set of instants. An instant can be seen as an event occurrence called a “tick�. It may represent any repetitive event in a system. Events may refer even to “classical� time dimension or to some evolution of a hardware part (rotation of crankshaft, distance …). Figure 1 presents the modeling elements and their relationships.

Figure 1. TADL2 metamodel for Timebase and dimension definition.
The type of a TimeBase is a Dimension (see Figure 10). The Dimension has a kind that represents the nature of the TimeBase. Of course, Time, Angle and Distance which are often used in the automotive domain are proposed. Additionally, Logical can be used to define a logical time reference. In particular, logical can be used to describe the units mentioned in the AUTOSAR metamodel. Finally, other can be used for very specific applications.

Figure 2. Part of the TADL2 Metamodel for TimeBase Relations.
The TimeBaseRelation (see Figure 2) is used to give equivalence between different Timebases. More precisely, it specifies equality between a left and a right TimingExpression.
Links to TADL2 concepts
See supporting material TADL constraints, below.
Abstraction level specific list of applicable events
See supporting material Abstraction level specific list of events, below.
Context Specific Example
A textual concrete syntax for TADL2 is provided for defining timebases.
Refering the BBW example, and timing constraints TC. 1 to TC. 8 there are up to three different timebases in the system, all based on a common Dimension (physicalTime).
Listing 1. Example of Dimension
Listing 1 shows the dimension declaration. A list of units and attributes for their conversion expression are given saying that there is a conversion for micros, millisecond (ms) and second in the physicalTime dimension (see lines 13 - 15).
Listing 2. Example of Dimension
The Dimension declaration is easily extendable to add new units but some of them (time, angle) are frequently used in a system. The objective would be to develop once and for all the Dimension definition including the different units. This can be done through dedicated libraries.
Based on this dimension type, the TimingSpecification declares three Timebases (see TimeBase chrono_time {
). The chrono_time timebase is declared with a type physicalTime (see lines 20-30). The second timebase is universal_time timebase which is the reference timebase for the whole system (see lines 32-36). The third timebase model the Ecus clocks.
For all timebases, a precisionFactor and a precisionUnit are given. For the universal_time timebase, the precision means that this timebase is able to specify value with a precision of 0.1 micro second. .
Time bases can be related to each other by either constant values or dynamic relations (example dependency between °CRK and engine round per minute speed). Expressing relationship between timebases is mandatory for building a global perception of time and ensuring a time safe cooperation over the platform.
Listing 4. Example of TimeBase Relation |