Image Processing Reference
In-Depth Information
same ECU from each other in the value (memory protection) and in the temporal (execution time
monitoring) domain.
Input/Output
(
I/O
)
library and drivers
: he HIS I/O library provides a standardized interface to access
the respective low-level drivers.
Flash driver
: he specification of the standardized HIS flash driver describes a standard interface of
services required for flash programming.
Controller area network
(
CAN
)
driver
: he HIS CAN driver provides data-link layer services for the
transmission and the reception of frames on CAN [,] networks.
In the following, each of the listed HIS components is briefly described.
18.4.1 Protected OSEK
HIS defines extensions to the OSEK OS specification to protect separate application tasks running
on the same ECU []. [].These extensions:
•
Provide means to prevent different application tasks within the same ECU to corrupt each
other's data.
•
Monitor and restrict the execution time of each single application task.
•
Exclusively assign operating system resources to a single application task and prevent all
other application tasks from accessing these resources.
To fulfill these services, the protected OSEK OS, however, requires hardware support, namely, a
memory protection unit and the existence of multiple processor modes (e.g., a privileged mode for
the OS and a nonprivileged mode for the application tasks). For the monitoring and the restriction
of the execution time of each task, an OS timer is assigned to each task to trace the task's execution
time and abort the task in case the task exceeds its statically assigned execution time budget.
18.4.2 I/O Library and Drivers
he HIS I/O library [] is intended to provide a standard interface to low-level drivers (e.g., for dig-
ital I/O). he I/O library supports both synchronous (i.e., the caller of the library function is blocked
till the function completes) and asynchronous (i.e., the caller of the library function just triggers the
function, and is asynchronously informed once the I/O operation has completed) operation. In case
of asynchronous operation, the I/O library itself takes care of the required buffer handling to decou-
ple the calling function from the called driver. he I/O library and the corresponding drivers provide
the following API functions:
Init
: This API function is used for the initialization of the controlled device. The function must be
called prior to any other service.
Deinit
: his API function is used to de-initialize the controlled device. he function has to be called
upon releasing of the device (e.g., prior to termination of the application).
Read
:hisAPIfunctionisusedtoreaddatafromthecontrolleddevice.hesemanticsofthisfunction
is similar to the UNIX
read(2)
system call.
Write
:hisfunctionsisusedtowritedatatothecontrolleddevice.hesemanticsofthisfunctionis
similar to the UNIX
write(2)
system call.
Ioctl
: This function can be used to access other services provided by the respective driver, which
cannot be mapped to the semantics of any of the previously described API functions. he semantics
of this function is similar to the UNIX
ioctl(2)
system call.
