Clarify the difference between when-equations and clocked when-equati…

…ons.

Closes modelica#3001

chapters/equations.tex

@@ -200,6 +200,7 @@ \subsection{When-Equations}\label{when-equations}
 \end{lstlisting}
 
 The \lstinline!expression! of a \lstinline!when!-equation shall be a discrete-time \lstinline!Boolean! scalar or vector expression.
+If \lstinline!expression! is a clocked expression it is handled differently, see \cref{clocked-when-clause}.
 The equations within a \lstinline!when!-equation are activated only at the instant when the scalar expression or any of the elements of the vector expression becomes true.
 
 \begin{example}

chapters/synchronous.tex

@@ -840,7 +840,7 @@ \subsection{Sub-Clock Conversion Operators}\label{sub-clock-conversion-operators
 
 \section{Clocked When-Clause}\label{clocked-when-clause}
 
-In addition to the previously discussed conditional \lstinline!when!-clause, a \emph{clocked} \lstinline!when!-clause\index{clocked!when-clause@\robustinline{when}-clause}\index{when-clause@\robustinline{when}-clause!clocked} is introduced:
+In addition to the previously discussed conditional \lstinline!when!-clause (see \cref{when-equations}), a \emph{clocked} \lstinline!when!-clause\index{clocked!when-clause@\robustinline{when}-clause}\index{when-clause@\robustinline{when}-clause!clocked} is introduced:
 % TODO: Can't have angle brackets and \emph in the same mathescape due to LaTeXML issue:
 % - https://github.com/brucemiller/LaTeXML/issues/1477
 % Once we cut the MathJax dependency, change to single mathescape for better character spacing.