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  • 2 commits
  • 2 files changed
  • 2 contributors

Commits on Apr 24, 2021

  1. Addition of SWD documentation

    @mubes
    mubes committed Apr 24, 2021
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    6b90aeb View commit details

  2. Merge pull request #26 from mubes/swd_docs 

    Addition of SWD documentation
    @azonenberg
    azonenberg authored Apr 24, 2021
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    e0df671 View commit details
Showing with 80 additions and 2 deletions.
  1. BIN images/filters/swd.png
  2. +80 −2 section-decodes.tex
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82 changes: 80 additions & 2 deletions section-decodes.tex
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@@ -998,9 +998,87 @@ \subsection{Output Signal}
\pagebreak
\section{SWD}

The Serial Wire Debug protocol, commonly used for debugging of low-pin-count ARM microcontrollers.
The Serial Wire Debug protocol between a Debug Probe and an ARM Microcontroller, typically from the CORTEX-M family. This
decode recognises all SWD frame elements and validates type and parity of both incoming and outgoing messages. It also
identifies line resets and line protocol change messages.

The SWD Protocol defines that the target will read and write on the rising edge of SWCLK. It does not place any constraint
on when the probe reads and writes. For the purposes of graphical depiction each protocol element starts at a falling edge
and continues to be valid until the next falling edge, following the graphical convention established in the ARM documentation.

Reference: ARM Debug Interface v5 Architecture Specification, Chapter 4.

\begin{figure}[h]
\centering
\includegraphics[width=16cm]{images/filters/swd.png}
\caption{Example of SWD protocol decode}
\label{filter_can}
\end{figure}

\subsection{Inputs}

\begin{tabularx}{16cm}{llX}
\thickhline
\textbf{Signal name} & \textbf{Type} & \textbf{Description} \\
\thickhline
SWDIO & Digital & Serial Wire Data In/Out (To/From target)\\
SWCLK & Digital & Serial Wire Clock In (To Target from Debug Probe)\\
\thickhline
\end{tabularx}

\subsection{Parameters}

No parameters are required for configuration of SWD. The protocol is clocked by SWCLK.

\subsection{Output Signal}

The SWD bus decode outputs a time series of SWD message elements, each of which may be one or a number of bits long.
Each message element consist of a type and optional numeric content.

\begin{tabularx}{16cm}{lllX}
\thickhline
\textbf{Type} & \textbf{Description} & \textbf{Color} & \textbf{Format} \\
\thickhline
Line Control & Line Reset & \cellcolor{preamble}\textcolor{white}{Preamble} & LINE RESET \\
\thickhline
Line Mode & Line Mode Change to SWD & \cellcolor{control}\textcolor{white}{Control} & JTAG TO SWD \\
\thickhline
Line Mode & Line Mode Change to JTAG & \cellcolor{control}\textcolor{white}{Control} & SWD TO JTAG \\
\thickhline
Line Mode & Line Mode Change to Dormant & \cellcolor{control}\textcolor{white}{Control} & SWD TO DORMANT \\
\thickhline
Line Mode & Leave Dormant Mode & \cellcolor{control}\textcolor{white}{Control} & LEAVE DORMANT \\
\thickhline
Start & Start of frame & \cellcolor{preamble}\textcolor{white}{Preamble} & START \\
\thickhline
APnDP & Selection between AP and DP & \cellcolor{control}\textcolor{white}{Control} & AP|DP \\
\thickhline
RnW & Read or Write mode & \cellcolor{control}\textcolor{white}{Control} & R|W \\
\thickhline
ADDR & AP or DP Address & \cellcolor{address}\textcolor{black}{Address} & Reg \%02x \\
\thickhline
Parity & Good Header Parity & \cellcolor{green}\textcolor{black}{Control} & OK \\
\thickhline
Parity & Bad Header Parity & \cellcolor{red}\textcolor{white}{Control} & BAD \\
\thickhline
Stop & End of Header & \cellcolor{preamble}\textcolor{white}{Preamble} & STOP \\
\thickhline
Park & Line Release & \cellcolor{preamble}\textcolor{white}{Preamble} & PARK \\
\thickhline
Turnaround & Line Direction Change & \cellcolor{preamble}\textcolor{white}{Preamble} & TURN \\
\thickhline
Acknowledge & Good Response from target to request & \cellcolor{control}\textcolor{white}{Control} & ACK|WAIT \\
\thickhline
Acknowledge & Bad Response from target to request & \cellcolor{control}\textcolor{white}{Control} & FAULT|ERROR \\
\thickhline
Data & Payload to/From Target & \cellcolor{data}\textcolor{white}{Data} & \%08x \\
\thickhline

\thickhline
\end{tabularx}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Reference: ARM Debug Interface v5 Architecture Specification, chapter 5.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\pagebreak