Image Processing Reference
In-Depth Information
Suspended
Terminate
Activate
Resume
Preempt
Preempted
Running
FIGURE .
OSEKtime task states.
to the
Preempted
state and stays there until the interrupting task is inished. his kind of schedul-
ing is called “stack-based scheduling”; no priorities are assigned to the tasks—only the activation
times define the precedence between different tasks.
18.3.5 OSEKtime FTCom
OSEKtime FTCom [] is the fault-tolerant real-time communication layer that accompanies OSEK-
time OS. Similar to OSEK COM, OSEKtime FTCom can be used for both external and internal
communication. In contrast to OSEK COM, OSEKtime FTCom solely supports “time-driven sig-
nal transmission”. In case of external communication, the interaction sublayer of OSEKtime FTCom
takes care of the representational issues of signals like byte ordering and alignment. On the sender's
side, this layer converts signals from the byte order of the sending ECU into the network byte order.
Furthermore, the interaction layer packs multiple signals into a single communication frame to
reduce communication bandwidth consumption. Additionally in case of external communication,
the “fault tolerance sublayer” of OSEKtime FTCom manages all fault tolerance issues, namely signal
replication and signal reduction. On the sender's side, this layer replicates a single application signal
andthusproducesmultiplesignalinstances.hesesignalinstancesarehandedovertotheinteraction
sublayer for byte order conversion and packing. Afterwards, the signal instances are transmitted via
redundant communication paths. Hereby, temporal redundancy (multiple transmissions on a single
communication channel) and spatial redundancy (transmission on multiple communication chan-
nels) can be distinguished. On the receiver's side, multiple signal instances are collected from the
interaction sublayer and reduced to obtain a single application signal, which is handed on to the
application layer.
18.4 HIS
The HIS working group has been formed by their members to “bundle their activities for standard
software modules, process maturity levels, software test, software tools, and programming of control
units. he common goal is to achieve and use joint standards.” Different from the OSEK/VDX work-
ing group, HIS solely includes car manufacturers (OEMs) as members. he components standardized
by HIS are listed in the following:
Protected OSEK OS
: The protected OSEK OS specification defines additional mechanisms and ser-
vices (in addition to the conventional OSEK OS) to protect separate applications running on the
