Service Processes for the SBB Implemented as Service Functions. ETAS INTECRIO

ETAS Bypass Concept

So, if a preemptive task of higher priority interrupts the tasks containing the bypass service, it will see the ECU value instead of the bypass value. The probability of this inconsistency depends on the distance between the two writes.

Interrupting task

Bypass

Fn*

ECU

Fn

8.6.1

time

Fig. 8-5 Possible data inconsistency (the small arrows ( waiting time for bypass results)

) indicate a

A countermeasure to this problem is disabling the ECU function, so that only the bypass is writing to the bypassed ECU values (see below). Be aware that disabling the ECU function implies other safety constraints in case of bypass failures as discussed below.

Service Processes for the SBB Implemented as Service

Functions

For SBB, the way of ECU implementation is to replace the ECU process to be bypassed by a container process that contains service function calls before and after it calls the original ECU process. This allows to call the ECU process under certain conditions only, e.g. to deactivate it in case of possible data consistency problems. To simulate the timing behavior of the disabled ECU process, a delay time can be configured.

Therefore, the suggested ECU implementation looks like this:

Fn*

Bypass

Fn

ECU

time

Fig. 8-6 Suggested SBB implementation

INTECRIO V4.7 - User’s Guide 151