Improve description of cmderr "busy"

debug_module.adoc

@@ -84,7 +84,7 @@ While the reset is on-going, harts are either in the running state,
 indicating it's possible to perform some abstract commands during this
 time, or in the unavailable state, indicating it's not possible to
 perform any abstract commands during this time. Once a hart's reset is
-complete, `havereset` becomes set. When a hart comes out of reset and {dmcontrol-haltreq} or `resethaltreq` 
+complete, `havereset` becomes set. When a hart comes out of reset and {dmcontrol-haltreq} or `resethaltreq`
 are set, the hart will immediately enter Debug Mode (halted state).
 Otherwise, if the hart was initially running it will execute normally
 (running state) and if the hart was initially halted it should now be
@@ -328,13 +328,17 @@ that case, the command will return "not supported".
 ====
 
 Debuggers execute abstract commands by writing them to {dm-command}. They can
-determine whether an abstract command is complete by reading {abstractcs-busy} in {dm-abstractcs}. If the debugger starts a new command while {abstractcs-busy} is set, {abstractcs-cmderr} becomes 1 (busy), the
-currently executing command still gets to run to completion, but any
-error generated by the currently executing command is lost. After
+determine whether an abstract command is complete by reading {abstractcs-busy} in {dm-abstractcs}. After
 completion, {abstractcs-cmderr} indicates whether the command was successful or not.
 Commands may fail because a hart is not halted, not running,
 unavailable, or because they encounter an error during execution.
 
+If the debugger attempts to start a new command while {abstractcs-busy} is set,
+the new command will not get started and the currently executing command still
+gets to run to completion. After the command finishes, {abstractcs-cmderr}
+will contain 1 (busy), and any error generated by the completed command will
+be lost.
+
 If the command takes arguments, the debugger must write them to the
 `data` registers before writing to {dm-command}. If a command returns results, the
 Debug Module must ensure they are placed in the `data` registers before {abstractcs-busy}
@@ -393,7 +397,7 @@ determines the kind of command. <<tab:cmdtype>> lists all commands.
 .Meaning of {command-cmdtype}
 [%autowidth,float="center",align="center",cols=">,<",options="header"]
 |===
-| {command-cmdtype} | Command 
+| {command-cmdtype} | Command
 | 0 | <<ac-accessregister, Access Register Command>>
 | 1 | <<ac-quickaccess, Quick Access>>
 | 2 | <<ac-accessmemory, Access Memory Command>>
@@ -555,7 +559,7 @@ effects, use the following procedure:
 .. Read {dm-dmcontrol} until {dmcontrol-dmactive} is high.
 . Read {dm-dmstatus}, which contains {dmstatus-version}.
 
-If it was necessary to clear {dmcontrol-ndmreset}, this might have the following  
+If it was necessary to clear {dmcontrol-ndmreset}, this might have the following
 side effects:
 
 . {dmcontrol-haltreq} is cleared, potentially preventing a halt request made by a previous debugger from taking effect.

xml/dm_registers.xml

@@ -470,8 +470,7 @@ same project unless stated otherwise.
 
     <register name="Abstract Control and Status" short="abstractcs" address="0x16">
         Writing this register while an abstract command is executing causes
-        {abstractcs-cmderr} to become 1 (busy) once the command completes
-        ({abstractcs-busy} becomes 0).
+        {abstractcs-cmderr} to contain 1 (busy) once the command completes.
 
         [NOTE]
         ====
@@ -527,7 +526,6 @@ same project unless stated otherwise.
             An abstract command was executing while {dm-command},
             {dm-abstractcs}, or {dm-abstractauto} was written, or when one
             of the `data` or `progbuf` registers was read or written.
-            This status is only written if {abstractcs-cmderr} contains 0.
             </value>
 
             <value v="2" name="not supported">
@@ -572,8 +570,7 @@ same project unless stated otherwise.
         executed.
 
         Writing this register while an abstract command is executing causes
-        {abstractcs-cmderr} to become 1 (busy) once the command completes
-        (busy becomes 0).
+        {abstractcs-cmderr} to contain 1 (busy) once the command completes.
 
         If {abstractcs-cmderr} is non-zero, writes to this register are ignored.
 
@@ -608,8 +605,7 @@ same project unless stated otherwise.
 
         If this register is written while an abstract command is executing
         then the write is ignored and
-        {abstractcs-cmderr} becomes 1 (busy) once the command completes
-        (busy becomes 0).
+        {abstractcs-cmderr} will contain 1 (busy) once the command completes.
 
         <field name="autoexecprogbuf" bits="31:16" access="WARL" reset="0">
             When a bit in this field is 1, read or write accesses to the
@@ -677,7 +673,7 @@ same project unless stated otherwise.
         registers.
 
         Accessing these registers while an abstract command is executing causes
-        {abstractcs-cmderr} to be set to 1 (busy) if it is 0.
+        {abstractcs-cmderr} to contain 1 (busy) once the command completes.
 
         Attempts to write them while {abstractcs-busy} is set does not change their value.
 
@@ -712,7 +708,7 @@ same project unless stated otherwise.
         implemented starting at {dm-progbuf0}, counting up.
 
         Accessing these registers while an abstract command is executing causes
-        {abstractcs-cmderr} to be set to 1 (busy) if it is 0.
+        {abstractcs-cmderr} to contain 1 (busy) once the command completes.
 
         Attempts to write them while {abstractcs-busy} is set does not change their value.