System Console over JTAG fails to execute master_write_32 — can't do this while target is running?

Question

I had a simple controller written in Verilog that was configuring Altera's TSE MAC. Up to this point, it was fairly simple. However, what I wanted to do next is to set a lot of Marvel PHY's settings as well as keep monitoring both PHY and MAC for statistics and errors, etc. Doing that in HW seems like an overkill, so I have decided to incorporate a Nios CPU. But before going ahead and implementing the component in software, I wanted to quickly prototype the idea using System Console. Anyhow, here is my QSys base system:

The MAC instance is called tse_mac and the idea is to configure it by reading/writing to control_port through CPU's data_master.

After getting the system up and running, I've connected to it using System Console. I assume it generally works because it is able to get master service path:

% get_service_paths master
{/devices/EP2AGX260@1#7-1/(link)/JTAG/(70:34 v3 #0)/nios2_0}

It also opens fine. However, it fails right away when trying to write 32-bit value:

% get_service_paths master
{/devices/EP2AGX260@1#7-1/(link)/JTAG/(70:34 v3 #0)/nios2_0}
% open_service master "/devices/EP2AGX260@1#7-1/(link)/JTAG/(70:34 v3 #0)/nios2_0"

% master_write_32 "/devices/EP2AGX260@1#7-1/(link)/JTAG/(70:34 v3 #0)/nios2_0" 0x400 0x00000000;
error: com.altera.systemconsole.internal.plugin.jtag.oci.Nios2DebugException: Can't do this while target is running
    while executing
"master_write_32 {/devices/EP2AGX260@1#7-1/(link)/JTAG/(70:34 v3 #0)/nios2_0} {0x400} {0x00000000}"
    while executing
"master_write_32 "/devices/EP2AGX260@1#7-1/(link)/JTAG/(70:34 v3 #0)/nios2_0" 0x400 0x00000000"
% 

Here is the exception:

Jul 22, 2012 12:17:39 PM com.altera.systemconsole.internal.core.SystemConsole logSevere
SEVERE: com.altera.systemconsole.internal.plugin.jtag.oci.Nios2DebugException: Can't do this while target is running
java.util.concurrent.ExecutionException: com.altera.systemconsole.internal.plugin.jtag.oci.Nios2DebugException: Can't do this while target is running
    at com.altera.systemconsole.internal.core.SimpleFuture$Sync.innerGet(SimpleFuture.java:169)
    at com.altera.systemconsole.internal.core.SimpleFuture.get(SimpleFuture.java:66)
    at com.altera.systemconsole.scripting.StandardCommandSet.waitForFutureResponse(StandardCommandSet.java:233)
    at com.altera.systemconsole.scripting.StandardCommandSet.peekMemoryService(StandardCommandSet.java:161)
    at com.altera.systemconsole.scripting.StandardCommandSet.readByte(StandardCommandSet.java:120)
    at com.altera.systemconsole.scripting.ScriptEngine$16.execute(ScriptEngine.java:1117)
    at com.altera.systemconsole.scripting.ScriptEngine$LegacyCommandAdapter.execute2(ScriptEngine.java:199)
    at com.altera.systemconsole.scripting.SystemConsoleThreadTCLInterpreter$2$1.run(SystemConsoleThreadTCLInterpreter.java:181)
    at com.altera.systemconsole.internal.core.SystemExecutor$4.run(SystemExecutor.java:516)
    at com.altera.systemconsole.internal.core.SystemExecutor$ComparableTask.run(SystemExecutor.java:148)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Caused by: com.altera.systemconsole.internal.plugin.jtag.oci.Nios2DebugException: Can't do this while target is running
    at com.altera.systemconsole.internal.plugin.jtag.oci.Nios2Debug.readMemoryIndirect(Native Method)
    at com.altera.systemconsole.internal.plugin.jtag.oci.Nios2Debug.readMemory(Nios2Debug.java:186)
    at com.altera.systemconsole.internal.plugin.jtag.oci.OciMemoryService.peek(OciMemoryService.java:158)
    at com.altera.systemconsole.internal.core.legacymaster.LegacyMasterChannel$1.run(LegacyMasterChannel.java:88)
    at com.altera.systemconsole.internal.core.SystemExecutor.addTaskIfNecessary(SystemExecutor.java:536)
    at com.altera.systemconsole.internal.core.legacymaster.LegacyMasterChannel.doReadMemory(LegacyMasterChannel.java:77)
    at com.altera.systemconsole.internal.core.legacymaster.LegacyMasterChannel.readMemory(LegacyMasterChannel.java:69)
    at com.altera.systemconsole.scripting.StandardCommandSet.peekMemoryService(StandardCommandSet.java:157)
    ... 9 more

I have never used System Console before and could not find anything related on the Internet or in the manual. So the question is — what wrongdoing am I committing? Any help solving the problem is appreciated.

Answer 1

The exception means that you have to pause/stop CPU to execute master_write_32. To keep the CPU running, JTAG to Avalon Master Bridge must be used. It will get exported as another service (i.e. with index 1) and can be used to communicate with Avalon MM component. The credit for an answer goes to guys at Altera's forum.