cpu: ext_reg switch bug FIX by markus

[calu.git] / 2_isa / callingconv.tex

diff --git a/2_isa/callingconv.tex b/2_isa/callingconv.tex
index 794edf79665b1e63083486d1ff3aaeb1749d4ff6..951ef0beec7fc9a4288017aa7eb4e7057c36cbcc 100644 (file)
--- a/2_isa/callingconv.tex
+++ b/2_isa/callingconv.tex
@@ -1,9 +1,11 @@
-\section{calling convention}
+\section{Calling Convention}
+
+Programs and functions implementing this instruction set, should implement the following calling conventions. The register usage should be done as stated in table~\ref{tab:callcon}. If the callee should be given more than five parameters, other parameters should be passed over by the stack.
 
 \begin{table}[ht]
        \centering
        \begin{tabular}{|c|c|c|} \hline
-               Register & saved by & usage  \\ \hline
+               \textbf{register} & \textbf{saved by} & \textbf{usage} \\ \hline
                r0       & caller   & return \\ \hline
                r1       & caller   & first parameter \\ \hline
                r2       & caller   & second parameter \\ \hline
@@ -21,6 +23,64 @@
                r14      & callee   & \\ \hline
                r15      & callee   & \\ \hline
        \end{tabular}
-       \caption{Register save \ldots}
-%      \label{tab:<+label+>}
+       \caption{Calling Convention}
+       \label{tab:callcon}
+\end{table}
+
+\subsection{Assembler  Syntax}
+\begin{itemize}
+\item \textbf{Immediate s}: decimal \texttt{12345}, hex \texttt{0xabcde123},
+binary \texttt{0b10101110}\\
+If an immediate is to large for the given instruction the assembler terminates
+with an error
+
+\item \textbf{High and Low Half Word}: you can use the suffix \texttt{@hi} to
+access the upper 16 bit of an immediate, or \texttt{@lo} to access the lower 16
+bit.
+
+\item \textbf{Memory access}: to access data on an address which is located in a
+register, you have to write \texttt{0(rS)}. Alternatively you can specify
+a signed displacement.
+
+\item \textbf{Expressions}: Usual expressions like \texttt{+}, \texttt{-},
+\texttt{*} or \texttt{<<} will be evaluated by the assembler, e.g. \texttt{ldw
+r1, 0x20-8(r3)} is a valid instruction
+\end{itemize}
+
+\subsection{Directives}
+In order to gain extra comfort, several directives are interpreted by the
+assembler, a list is given in table~\ref{tab:asmdirs}.
+\begin{table}[ht]
+       \centering
+       \begin{tabular}{|l|p{10cm}|} \hline
+               \textbf{Name} & \textbf{Description} \\ \hline
+               \texttt{.data} & subsequent data is desired for the data memory\\ \hline
+               \texttt{.text} & subsequent code is desired for the instruction memory\\ \hline
+               \verb+.include "file.s"+ & include a further file \\ \hline
+               \texttt{.org \textit{addr}} & move \textit{forward} to a specific
+               address in data or instruction memory, depending on the current
+               section \\ \hline
+
+               \texttt{.fill \textit{repeat}, \textit{value}} & place a
+               32 bit value \texttt{\textit{repeat}}-times, while
+               \texttt{\textit{repeat}} is optional.
+
+               When one parameter is given, the value is placed at the current address.
+               Note that a given value will be rounded up to a full byte, e.g.
+               \texttt{0x123} occupy two bytes.
+
+               When two parameters are given, the first equals \texttt{\textit{repeat}}
+               and the second corresponds to \texttt{\textit{value}} \\ \hline
+
+               \texttt{.define \textit{name}, \textit{value}} & define a constant. Note
+               that a define isn't equal to a label\\ \hline
+
+               \texttt{label: <instr/data>} & label an instruction or data. The label
+               can be used as an alias for the address of this instruction in the
+               instruction memory or as a reference in the data memory, depending on
+               the current section\\ \hline
+       \end{tabular}
+       \caption{supported directives by the assembler}
+       \label{tab:asmdirs}
 \end{table}
+