Commit 91650223 authored by rene.zurbruegg undefined's avatar rene.zurbruegg undefined Committed by overleaf
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Update on Overleaf.

parent 2b485f8f
......@@ -135,5 +135,40 @@ It also decides which interrupt has priority and what interrupt service routine
\textbf{Interrupt VS Polling}
\item swa
\item Utilization \textbf{u}: average percentage the processor is busy
\item Computation \textbf{c}: processing time for the event
\item Overhead \textbf{h}: Time overhead due to interrupt
\item Period \textbf{P}: Polling period
\item Interval time \textbf{T}: Minimal time between two events
\item Deadline \textbf{D}: Maximal time between event arrival and finishing
Average Utilization: $\underline{u} = \frac{c}{P}$ \\
Limitation: $2c \leq c + P \leq D \leq T $ \\
Average Utilization: $\underline{u} = \frac{h + c}{T}$ \\
Limitation: $ h + c \leq D \leq T $\\
\textbf{Problem} \\
Often \verb|D| ,\verb|T|, \verb|c| and \verb|h| are given: \\
$D < min(c,h) \rightarrow \texttt{Impossible}$ \\
$2c \leq D < h + c \rightarrow \texttt{Polling with:} u = \frac{c}{D-c}$ \\
$ h + c \leq D < 2c \rightarrow \texttt{Interrupt with:} u = \frac{h + c}{T}$\\
$ c + max(c,h) \leq D \rightarrow \texttt{Both possible with:} u_p = \frac{c}{D-c}, u_i = \frac{h+c}{T}$
\ownsubsection{Clocks and Timers (3-60)}
\textbf{Watchdog Timer (*-65)} \\
A Watchdog timer is a timer that runs in the background and as soon as it rolls over, it resets the state of the CPU. \\
These timer are often used for safety purposes since it makes sure that even if a program crashed or entered a infinity loop, the processor will recover. \\
A watchdog timer must continously be reset by the application as prrof that it is still working as expected. \\
\textbf{Timers} \\
Timers are used for:
\item Capture the current time or time differences
\item Generate interrupts when certain limits are reached
\item Generate interrupts when overflow
\item Generate output signals (PWM)
\ No newline at end of file
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