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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
    <title>Target Communication Framework Services - Registers</title>
</head>

<body lang='EN-US'>
  
<h1>Target Communication Framework Services - Registers</h1>
 
<ul>
    <li><a href='#Cmds'>Commands</a>
    <ul>
        <li><a href='#CmdGetContext'>Get Context</a>
        <li><a href='#CmdGetChildren'>Get Children</a>
        <li><a href='#CmdSetRegister'>Set Register</a>
        <li><a href='#CmdGetRegister'>Get Register</a>
    </ul>
    <li><a href='#Events'>Events</a>
    <li><a href='#API'>API</a>
</ul>

<h1>Registers Service</h1>

<p>The service provides basic operations to read/write CPU and hardware registers. Command
and event parameters are encoded as zero terminated <a href='TCF Specification.html#JSON'>JSON</a> strings.</p>

<p>The service uses standard format for error reports,
see <a href='TCF Services.html#ErrorFormat'>Error Report Format</a>.</p>
 
<h2><a name='Cmds'>Commands</a></h2>

<h3><a name='CmdGetContext'>Get Context</a></h3>
 
<pre><b><font face="Courier New" size=2 color=#333399>
C  <i>&lt;token&gt;</i>  Registers  getContext  <i>&lt;string: context ID&gt;</i> 
</font></b></pre>

<p>The command retrieves context info for given context ID. A context corresponds to an
register, register group, register bit field, etc. Exact meaning of a context depends on the target.
Target agent should define contexts hierarchy that is:</p>
 
<ul type='disc'>
    <li>Adequately reflects target hardware registers layout;
    <li>Consistent with the lingo/terminology of the processor manuals;
    <li>Intuitive to a user.
</ul>
 
<p>Reply:</p>

<pre><b><font face="Courier New" size=2 color=#333399>
R  <i>&lt;token&gt;</i>  <i>&lt;error report&gt;</i>  <i>&lt;context data&gt;</i> 

<i>&lt;context data&gt;</i>
    <font face=Wingdings></font> null
    <font face=Wingdings></font> <i>&lt;object&gt;</i>
</font></b></pre>

<p>Context data object should, at least, contain member
<b><font face="Courier New" size=2 color=#333399>"ID" : <i>&lt;string&gt;.</i></font></b>
Context data is expected to be cached by clients.
Service sends contextChanged event to notify changes in context data.</p>

<p>Predefined register context properties are:</p>
<ul>
    <li><code><b><font face="Courier New" size=2 color=#333399>"ID" : <i>&lt;string&gt;</i></font></b></code>
    - ID of the context, same as getContext command argument.

    <li><code><b><font face="Courier New" size=2 color=#333399>"ParentID" : <i>&lt;string&gt;</i></font></b></code>
    - ID of a parent context.

    <li><code><b><font face="Courier New" size=2 color=#333399>"ProcessID" : <i>&lt;string&gt;</i></font></b></code>
    - process ID.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Name" : <i>&lt;string&gt;</i></font></b></code>
    - context name.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Description" : <i>&lt;string&gt;</i></font></b></code>
    - context description.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Formats" : <i>&lt;array of string&gt;</i></font></b></code>
    - value formats available for register get/set commands.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Readable" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if context value can be read.

    <li><code><b><font face="Courier New" size=2 color=#333399>"ReadOnce" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if reading the context (register) destroys its current value - it can be read only once.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Writeable" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if context value can be written.

    <li><code><b><font face="Courier New" size=2 color=#333399>"WriteOnce" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if register value can not be overwritten - every write counts.

    <li><code><b><font face="Courier New" size=2 color=#333399>"SideEffects" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if writing the context can change values of other registers.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Volatile" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if the register value can change even when target is stopped.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Float" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if the register value is a floating-point value.

    <li><code><b><font face="Courier New" size=2 color=#333399>"BigEndian" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if big endian, which means decreasing numeric significance with increasing bit number.

    <li><code><b><font face="Courier New" size=2 color=#333399>"LeftToRight" : <i>&lt;boolean&gt;</i></font></b></code>
    - true if the lowest numbered bit (i.e. bit #0 or bit #1, depending on "FirstBit" value) should be shown to user as the left-most bit.

    <li><code><b><font face="Courier New" size=2 color=#333399>"FirstBit" : <i>&lt;int&gt;</i></font></b></code>
    - 0 or 1. If the context has bit field children, bit positions of the fields can be zero-based or 1-based.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Bits" : <i>&lt;array of int&gt;</i></font></b></code>
    - if context is a bit field, contains the field bit numbers in the parent context.

    <li><code><b><font face="Courier New" size=2 color=#333399>"Values" : <i>&lt;array of named values&gt;</i></font></b></code>
    - predefined names (mnemonics) for some of context values.

</ul>

<h3><a name='CmdGetChildren'>Get Children</a></h3>
 
<pre><b><font face="Courier New" size=2 color=#333399>
C  <i>&lt;token&gt;</i>  Registers  getChildren  <i>&lt;string: parent context ID&gt;</i> 
</font></b></pre>

<p>The command requests a list of contexts available for registers access commands.</p>
 
<p>Parent context ID is usually a thread ID retrieved through Run Control Service or one
of context IDs retrieved by previous getChildren commands.
Contexts hierarchy can be simple plain list of registers, or it can form a tree of register groups, registers and bit fields.
It is up to target agent developers to choose layout that is most descriptive for a given target.</p>
 
<p>Reply:</p>
 
<pre><b><font face="Courier New" size=2 color=#333399>
R  <i>&lt;token&gt;</i>  <i>&lt;error report&gt;</i>  <i>&lt;array of context IDs&gt;</i> <i></i>

<i>&lt;array of context IDs&gt;</i>
    <font face=Wingdings></font> null
    <font face=Wingdings></font> [ ]
    <font face=Wingdings></font> [ <i>&lt;context ID list&gt;</i> ]
  
<i>&lt;context ID list&gt;</i>
    <font face=Wingdings></font> <i>&lt;string: context ID&gt;</i>
    <font face=Wingdings></font> <i>&lt;context ID list&gt;</i> , <i>&lt;string: context ID&gt;</i>

</font></b></pre>

<h3><a name='CmdSetRegister'>Set Register</a></h3>
 
<pre><b><font face="Courier New" size=2 color=#333399>
C  &lt;token&gt;  Registers  set  <i>&lt;string: context ID&gt;</i>  <i>&lt;string: value format&gt;</i>  <i>&lt;string: value&gt;</i> 
</font></b></pre>

<p>Writes value into given register context. Context ID must be one returned by getContexts.
Value format must be one that is supported by the register context.
Client can get list of supported formats from context attributes.</p>
  
<p>Result message:</p>
 
<pre><b><font face="Courier New" size=2 color=#333399>
R  <i>&lt;token&gt;</i>  <i>&lt;error report&gt;</i> 
</font></b></pre>

<p>Error report provides integer error code and a short, human readable explanation
of error.</p>

<h3><a name='CmdGetRegister'>Get Register</a></h3>
 
<pre><b><font face="Courier New" size=2 color=#333399>
C  &lt;token&gt;  Registers  get  <i>&lt;string: context ID&gt;</i>  <i>&lt;string: value format&gt;</i> 
</font></b></pre>

<p>Reads register value from given register context. Context ID must be one returned by getContexts.
Value format must be one that is supported by the register context.
Client can get list of supported formats from context attributes.</p>
 
<p>Result message:</p>
 
<pre><b><font face="Courier New" size=2 color=#333399>
R  <i>&lt;token&gt;</i>  <i>&lt;error report&gt;</i>  <i>&lt;string: value&gt;</i> 
</font></b></pre>

<p>Error report provides integer error code and a short, human readable explanation
of error. Value is formatted according to requested format.</p>

<h2><a name='Events'>Events</a></h2>
 
<p>Registers service broadcasts notification events when registers contexts are changed, and when
a register content is altered by "set" commands.</p>
 
<pre><b><font face="Courier New" size=2 color=#333399>
E  Registers  contextChanged 
E  Registers  registerChanged  <i>&lt;string: context ID&gt;</i> 
</font></b></pre>

<h2><a name='API'>API</a></h2>
 
<pre>
<font color=#3F5FBF>/**
 * IRegisters service provides access to target CPU register values and properties.
 */</font>
<font color=#7F0055>public interface</font> IRegisters <font color=#7F0055>extends</font> IService {

    <font color=#7F0055>static final</font> String NAME = "Registers";

    <font color=#3F5FBF>/**
     * Context property names.
     */</font>
    <font color=#7F0055>static final</font> String
        PROP_ID = "ID",
        PROP_PARENT_ID = "ParentID",
        PROP_PROCESS_ID = "ProcessID",
        PROP_NAME = "Name",
        PROP_DESCRIPTION = "Description",
        PROP_FORMATS = "Formats",
        PROP_READBLE = "Readable",
        PROP_READ_ONCE = "ReadOnce",
        PROP_WRITEABLE = "Writeable",
        PROP_WRITE_ONCE = "WriteOnce",
        PROP_SIDE_EFFECTS = "SideEffects",
        PROP_VOLATILE = "Volatile",
        PROP_FLOAT = "Float",
        PROP_BIG_ENDIAN = "BigEndian",
        PROP_LEFT_TO_RIGHT = "LeftToRight",
        PROP_FIST_BIT = "FirstBit",
        PROP_BITS = "Bits",
        PROP_VALUES = "Values";
        
    <font color=#3F5FBF>/**
     * Standard known formats for register data.
     */</font>
    <font color=#7F0055>static final</font> String
        FORMAT_BINARY   = "Binary",
        FORMAT_OCTAL    = "Octal",
        FORMAT_DECIMAL  = "Decimal",
        FORMAT_HEX      = "Hex",
        FORMAT_NATURAL  = "Natural";
    
    <font color=#3F5FBF>/**
     * Retrieve context info for given context ID.
     *   
     * <font color=#7F9FBF>@param</font> id  context ID. 
     * <font color=#7F9FBF>@param</font> done - call back interface called when operation is completed.
     */</font>
    IToken getContext(String id, DoneGetContext done);

    <font color=#3F5FBF>/**
     * Client call back interface for getContext().
     */</font>
    <font color=#7F0055>interface</font> DoneGetContext {
        <font color=#3F5FBF>/**
         * Called when contexts data retrieval is done.
         * <font color=#7F9FBF>@param</font> error  error description if operation failed, null if succeeded.
         * <font color=#7F9FBF>@param</font> context  context data.
         */</font>
        <font color=#7F0055>void</font> doneGetContext(IToken token, Exception error, RegistersContext context);
    }

    <font color=#3F5FBF>/**
     * Retrieve contexts available for registers commands.
     * A context corresponds to an execution thread, stack frame, registers group, etc.
     * A context can belong to a parent context. Contexts hierarchy can be simple
     * plain list or it can form a tree. It is up to target agent developers to choose
     * layout that is most descriptive for a given target. Context IDs are valid across
     * all services. In other words, all services access same hierarchy of contexts,
     * with same IDs, however, each service accesses its own subset of context's
     * attributes and functionality, which is relevant to that service.
     *  
     * <font color=#7F9FBF>@param</font> parent_context_id  parent context ID. Can be null 
     * to retrieve top level of the hierarchy, or one of context IDs retrieved
     * by previous getChildren commands.
     * <font color=#7F9FBF>@param</font> done - call back interface called when operation is completed.
     */</font>
    IToken getChildren(String parent_context_id, DoneGetChildren done);

    <font color=#3F5FBF>/**
     * Client call back interface for getChildren().
     */</font>
    <font color=#7F0055>interface</font> DoneGetChildren {
        <font color=#3F5FBF>/**
         * Called when contexts data retrieval is done.
         * <font color=#7F9FBF>@param</font> error  error description if operation failed, null if succeeded.
         * <font color=#7F9FBF>@param</font> context_ids  array of available context IDs.
         */</font>
        <font color=#7F0055>void</font> doneGetChildren(IToken token, Exception error, String[] context_ids);
    }
    
    <font color=#3F5FBF>/**
     * RegistersContext objects represent register groups, registers and bit fields. 
     */</font>
    <font color=#7F0055>interface</font> RegistersContext {
        <font color=#3F5FBF>/**
         * Get Context ID.
         * <font color=#7F9FBF>@return</font> context ID.
         */</font>
        String getID();
        
        <font color=#3F5FBF>/**
         * Get parent context ID.
         * <font color=#7F9FBF>@return</font> parent context ID.
         */</font>
        String getParentID();
        
        <font color=#3F5FBF>/**
         * Get context (register, register group, bit field) name.
         * <font color=#7F9FBF>@return</font> context name.
         */</font>
        String getName();
        
        <font color=#3F5FBF>/**
         * Get context description.
         * <font color=#7F9FBF>@return</font> context description.
         */</font>
        String getDescription();
        
        <font color=#3F5FBF>/**
         * Get value formats available for register get/set commands.
         * See FORMAT_* for knows format IDs definition.
         * <font color=#7F9FBF>@return</font> array of supported format IDs.
         */</font>
        String[] getAvailableFormats();
        
        <font color=#3F5FBF>/**
         * Check if context value can be read.
         * <font color=#7F9FBF>@return</font> true if can read value of the context.
         */</font>
        <font color=#7F0055>boolean</font> isReadable();
        
        <font color=#3F5FBF>/**
         * Check if reading the context (register) destroys its current value -
         * it can be read only once.
         * <font color=#7F9FBF>@return</font> true if read-once register.
         */</font>
        <font color=#7F0055>boolean</font> isReadOnce();
        
        <font color=#3F5FBF>/**
         * Check if context value can be written.
         * <font color=#7F9FBF>@return</font> true if can write value of the context.
         */</font>
        <font color=#7F0055>boolean</font> isWriteable();
        
        <font color=#3F5FBF>/**
         * Check if register value can not be overwritten - every write counts.
         * <font color=#7F9FBF>@return</font> true if write-once register.
         */</font>
        <font color=#7F0055>boolean</font> isWriteOnce();
        
        <font color=#3F5FBF>/**
         * Check if writing the context can change values of other registers. 
         * <font color=#7F9FBF>@return</font> true if has side effects.
         */</font>
        <font color=#7F0055>boolean</font> hasSideEffects();
        
        <font color=#3F5FBF>/**
         * Check if the register value can change even when target is stopped.
         * <font color=#7F9FBF>@return</font> true if the register value can change at any time.
         */</font>
        <font color=#7F0055>boolean</font> isVolatile();
        
        <font color=#3F5FBF>/**
         * Check if the register value is a floating-point value.
         * <font color=#7F9FBF>@return</font> true if a floating-point register.
         */</font>
        <font color=#7F0055>boolean</font> isFloat();
        
        <font color=#3F5FBF>/**
         * Check endianess of the context.
         * Big endian means decreasing numeric significance with increasing bit number. 
         * <font color=#7F9FBF>@return</font> true if big endian.
         */</font>
        <font color=#7F0055>boolean</font> isBigEndian();
        
        <font color=#3F5FBF>/**
         * Check if the lowest numbered bit (i.e. bit #0 or bit #1 depending on
         * getFirstBitNumber() value) should be shown to user as the left-most bit or
         * the right-most bit.
         * <font color=#7F9FBF>@return</font> true if the first bit is left-most bit.
         */</font>
        <font color=#7F0055>boolean</font> isLeftToRight();
        
        <font color=#3F5FBF>/**
         * If the context has bit field children, bit positions of the fields
         * can be zero-based or 1-based.
         * <font color=#7F9FBF>@return</font> first bit position - 0 or 1.
         */</font>
        <font color=#7F0055>int</font> getFirstBitNumber();
        
        <font color=#3F5FBF>/**
         * If context is a bit field, get the field bit numbers in parent context. 
         * <font color=#7F9FBF>@return</font> array of bit numbers.
         */</font>
        <font color=#7F0055>int</font>[] getBitNumbers();
        
        <font color=#3F5FBF>/**
         * A context can have predefined names (mnemonics) for some its values.
         * This method returns a list of such named values.
         * <font color=#7F9FBF>@return</font> array of named values or null.
         */</font>
        NamedValue[] getNamedValues();
        
        <font color=#3F5FBF>/**
         * Get complete map of context properties.
         * <font color=#7F9FBF>@return</font> map of context properties.
         */</font>
        Map&lt;String,Object&gt; getProperties();
        
        <font color=#3F5FBF>/**
         * Read value of the context.
         * <font color=#7F9FBF>@param</font> format - ID of a format to use for result value. 
         * <font color=#7F9FBF>@param</font> done - call back object.
         * <font color=#7F9FBF>@return</font> - pending command handle.
         */</font>
        IToken get(String format, DoneGet done);
        
        <font color=#3F5FBF>/**
         * Set value of the context.
         * <font color=#7F9FBF>@param</font> format - ID of a format used for value.
         * <font color=#7F9FBF>@param</font> value - value to write into the context.
         * <font color=#7F9FBF>@param</font> done - call back object.
         * <font color=#7F9FBF>@return</font> - pending command handle.
         */</font>
        IToken set(String format, String value, DoneSet done);
    }
    
    <font color=#3F5FBF>/**
     * A register context can have predefined names (mnemonics) for some its values.
     * NamedValue objects represent such values. 
     */</font>
    <font color=#7F0055>interface</font> NamedValue {
        <font color=#3F5FBF>/**
         * Get number associated with this named value.
         * <font color=#7F9FBF>@return</font> the value as a number.
         */</font>
        Number getValue();
        
        <font color=#3F5FBF>/**
         * Get name (mnemonic) of the value.
         * <font color=#7F9FBF>@return</font> value name.
         */</font>
        String getName();
        
        <font color=#3F5FBF>/**
         * Get human readable description of the value.
         * <font color=#7F9FBF>@return</font> value description.
         */</font>
        String getDescription();
    }
    
    <font color=#3F5FBF>/**
     * 'get' command call back interface.
     */</font>
    <font color=#7F0055>interface</font> DoneGet {
        <font color=#7F0055>void</font> doneGet(IToken token, Exception error, String value);
    }
    
    <font color=#3F5FBF>/**
     * 'set' command call back interface.
     */</font>
    <font color=#7F0055>interface</font> DoneSet {
        <font color=#7F0055>void</font> doneSet(IToken token, Exception error);
    }

    <font color=#3F5FBF>/**
     * Add registers service event listener.
     * <font color=#7F9FBF>@param</font> listener - event listener implementation.
     */</font>
    <font color=#7F0055>void</font> addListener(RegistersListener listener);

    <font color=#3F5FBF>/**
     * Remove registers service event listener.
     * <font color=#7F9FBF>@param</font> listener - event listener implementation.
     */</font>
    <font color=#7F0055>void</font> removeListener(RegistersListener listener);

    <font color=#3F5FBF>/**
     * Registers event listener is notified when registers context hierarchy
     * changes, and when a register is modified by the service commands. 
     */</font>
    <font color=#7F0055>interface</font> RegistersListener {

        <font color=#3F5FBF>/**
         * Called when register context properties changed.
         * Most targets have static set of registers and register properties.
         * Such targets never generate this event. However, some targets,
         * for example, JTAG probes, allow user to modify register definitions.
         * Clients should flush all cached register context data. 
         */</font>
        <font color=#7F0055>void</font> contextChanged();

        <font color=#3F5FBF>/**
         * Called when register content was changed and clients 
         * need to update themselves. Clients, at least, should invalidate
         * corresponding cached registers data.
         * Not every change is notified - it is not possible,
         * only those, which are not caused by normal execution of the debuggee.
         */</font>
        <font color=#7F0055>void</font> registerChanged(String context_id);
    }
}
</pre>

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