The NS (Nintendo User Interface Shell) system module is the first module launched from a CTR-NAND title after the FIRM processes are loaded (also see Bootloader). This module is launched by the pm process, with the titleID loaded from NS state(hard-coded TID initialized during applet TID-array initialization). NS first launches ErrDisp, then the menu. On retail the menu TID is loaded from NS state, while on dev/debug the menu TID is loaded from config. On dev-units if the menu TID block doesn't exist in config, NS will attempt to launch the alternate menu instead. The TID of the launched menu is then written to ACTIVEMENUTID. NS uses pm:app to launch titles.

NS will not trigger the fatal-error screen when launching the regular/alternate menu fails.

Like home menu NS is constantly running while the system is in 3DS-mode. When attempting to return to home-menu when the home-menu process isn't running(like when the process terminated/crashed), NS will trigger a fatal error.

Alternate menu

When launching the regular menu fails, NS will then attempt to launch the alternate menu. This title could be used as a recovery process, however it's normally not used after the factory.

At the factory for all 3DS systems, Test Menu is installed with this TID. On retail this title is eventually deleted during Factory Setup.

Auto-boot

After loading FIRM params and prior to launching ErrDisp/Home Menu, NS handles auto-booting titles. The same code called by APT:Reboot is used for launching FIRM here. When the UPDATEFLAG is set, NS will launch SAFE_MODE_FIRM with the application titleID set to the System Updater titleID for this region. When the UPDATEFLAG is not set, NS can auto-boot the following titles as well if 0x1FF80016 bit0 is set.

When bit1 and bit2 are value zero in 0x1FF80016, NS will launch the title specified by the FIRM parameters if the title-info is set. This FIRM launch is done after launching ErrDisp and Home Menu. Otherwise when 0x1FF80016 is value 2 and the output u8 from PTMSYSM command 0x08140000 is value 0, NS will boot the title specified from the TWL TLNC block from FIRMparams+0x300. This is the same TLNC block which DSi titles wrote to RAM+0x300 for launching other titles via the launcher title. When handling the TLNC block, NS will boot the 3DS System Settings title when the TLNC titleID is the DSi System Settings titleID(the region field in the TLNC TID is not checked/used). When the TLNC titleID is not System Settings, NS will convert the input DSi titleID-high to the 3DS TWL titleID-high(tidhigh = (TLNCtidhigh & 0x7FFF) | 0x48000), then launch TWL_FIRM to run the title. NS does not support launching from gamecard via TLNC.

NS Workaround

A "ns_workaround" was added in NS to workaround the flaw added with 5.0.0-11. When NS is loading before launching any ARM11 processes and certain Configuration Memory fields are set, NS will launch AM then use command AM:InstallNATIVEFIRM. NS will then execute the code called by APT:StartNewestHomeMenu, the code related to APT:PrepareToStartNewestHomeMenu is not executed here.

NS will only execute this code-path when 0x1FF80016 is value zero, when KERNEL_VERSIONMAJOR is value 2, and when KERNEL_VERSIONMINOR is less than 35. Therefore, this code-path is only executed when the running NATIVE_FIRM version is prior to 5.0.0-11.

NS Service "ns:s"

Command Header Available since system version Description
0x000100C0 1.0.0-0 - 2.0.0-2 LaunchFIRM
0x000200C0 1.0.0-0 - 2.0.0-2 LaunchTitle
0x00030000 1.0.0-0 - 2.0.0-2 TerminateApplication
0x00040040 1.0.0-0 - 2.0.0-2 TerminateProcess
0x000500C0 1.0.0-0 - 2.0.0-2 LaunchApplicationFIRM
0x00060042 1.0.0-0 - 2.0.0-2 SetFIRMParams4A0
0x00070042 1.0.0-0 - 2.0.0-2 CardUpdateInitialize
0x00080000 1.0.0-0 - 2.0.0-2 CardUpdateShutdown
0x00090000 1.0.0-0 - 2.0.0-2 Gamecard system update related.
0x000A0000 1.0.0-0 - 2.0.0-2 Gamecard system update related.
0x000B0000 1.0.0-0 - 2.0.0-2 Gamecard system update related.
0x000C0000 1.0.0-0 - 2.0.0-2 Gamecard system update related.
0x000D0140 1.0.0-0 - 2.0.0-2 SetTWLBannerHMAC
0x000E0000 1.0.0-0 - 2.0.0-2 ShutdownAsync
0x000F0000 1.0.0-0 - 2.0.0-2 This calls APT:AppletUtility with fixed input params.
0x00100180 1.0.0-0 - 2.0.0-2 RebootSystem
0x00110100 1.0.0-0 - 2.0.0-2 TerminateTitle
0x001200C0 ? SetApplicationCpuTimeLimit
0x00130000 ? ?
0x00140042 ? ?
0x00150140 ? LaunchApplication
0x00160000 8.0.0-18 RebootSystemClean

The maximum sessions that can be used with this service is two, therefore only two processes can use this service at the same time.

NS Service "ns:p"

Command Header Description
0x00010040 ?
0x00020000 ShutdownAsync

This was added with 3.0.0-5. The PTM sysmodule connects to this service, and syncs whenever ptm:s GetShellState() changes.

NS Service "ns:c"

This was added with 5.0.0-11, it's unknown what this is used for.

APT Services

Command Header Available since system version Accessible with APT:U Description
0x00010040 Yes GetLockHandle
0x00020080 See here. Initialize
0x00030040 Yes Enable
0x00040040 Yes Finalize
0x00050040 Yes GetAppletManInfo
0x00060040 Yes GetAppletInfo
0x00070000 Yes GetLastSignaledAppletId
0x00080000 Yes CountRegisteredApplet
0x00090040 Yes IsRegistered
0x000A0040 Yes GetAttribute
0x000B0040 Yes InquireNotification
0x000C0104 Yes SendParameter
0x000D0080 Yes ReceiveParameter
0x000E0080 Yes GlanceParameter
0x000F0100 Yes CancelParameter
0x001000C2 Yes DebugFunc
0x001100C0 Yes MapProgramIdForDebug
0x00120040 Yes SetHomeMenuAppletIdForDebug
0x00130000 Yes GetPreparationState
0x00140040 Yes SetPreparationState
0x00150140 No PrepareToStartApplication
0x00160040 Yes PreloadLibraryApplet
0x00170040 Yes FinishPreloadingLibraryApplet
0x00180040 Yes PrepareToStartLibraryApplet
0x00190040 Yes PrepareToStartSystemApplet
0x001A0000 Yes PrepareToStartNewestHomeMenu
0x001B00C4 Yes StartApplication
0x001C0000 Yes WakeupApplication
0x001D0000 Yes CancelApplication
0x001E0084 Yes StartLibraryApplet
0x001F0084 Yes StartSystemApplet
0x00200044 Yes StartNewestHomeMenu
0x00210000 No OrderToCloseApplication
0x00220040 Yes PrepareToCloseApplication
0x00230040 Yes PrepareToJumpToApplication
0x00240044 Yes JumpToApplication
0x002500C0 Yes PrepareToCloseLibraryApplet
0x00260000 Yes PrepareToCloseSystemApplet
0x00270044 Yes CloseApplication
0x00280044 Yes CloseLibraryApplet
0x00290044 Yes CloseSystemApplet
0x002A0000 Yes OrderToCloseSystemApplet
0x002B0000 Yes PrepareToJumpToHomeMenu
0x002C0044 Yes JumpToHomeMenu
0x002D0000 Yes PrepareToLeaveHomeMenu
0x002E0044 Yes LeaveHomeMenu
0x002F0040 Yes PrepareToLeaveResidentApplet
0x00300044 Yes LeaveResidentApplet
0x00310100 Yes PrepareToDoApplicationJump
0x00320084 Yes DoApplicationJump
0x00330000 Yes GetProgramIdOnApplicationJump
0x00340084 Yes SendDeliverArg
0x00350080 Yes ReceiveDeliverArg
0x00360040 Yes LoadSysMenuArg
0x00370042 Yes StoreSysMenuArg
0x00380040 Yes PreloadResidentApplet
0x00390040 Yes PrepareToStartResidentApplet
0x003A0044 Yes StartResidentApplet
0x003B0040 Yes CancelLibraryApplet
0x003C0042 Yes SendDspSleep
0x003D0042 Yes SendDspWakeUp
0x003E0080 Yes ReplySleepQuery
0x003F0040 Yes ReplySleepNotificationComplete
0x00400042 Yes SendCaptureBufferInfo
0x00410040 Yes ReceiveCaptureBufferInfo
0x00420080 Yes SleepSystem
0x00430040 Yes NotifyToWait
0x00440000 Yes GetSharedFont
0x00450040 Yes GetWirelessRebootInfo
0x00460104 Yes Wrap
0x00470104 Yes Unwrap
0x00480100 No GetProgramInfo
0x00490180 No Reboot
0x004A0040 Yes GetCaptureInfo
0x004B00C2 Yes AppletUtility
0x004C0000 Yes SetFatalErrDispMode
0x004D0080 Yes GetAppletProgramInfo
0x004E0000 Yes HardwareResetAsync
0x004F0080 2.2.0-X Yes SetApplicationCpuTimeLimit
0x00500040 2.2.0-X Yes GetApplicationCpuTimeLimit
0x00510080 3.0.0-5 Yes GetStartupArgument
0x00520104 4.0.0-7 Yes Wrap1
0x00530104 4.0.0-7 Yes Unwrap1
0x00540040 5.0.0-11 ? ?
0x00550040 7.0.0-13 Yes This writes the input u8 to a NS state field.
0x00560000 7.0.0-13 Yes This returns an u8 NS state field(which can be set by cmd 0x00550040), at cmdreply+8.
0x00570044 7.0.0-13 ? WakeupApplication2?
0x00580002 7.0.0-13 Yes GetProgramID
0x01010000 8.0.0-18 Yes CheckNew3DSApp
0x01020000 8.0.0-18 Yes CheckNew3DS
0x01030000 8.0.0-18 Yes ?
0x01040000 8.0.0-18 ? IsStandardMemoryLayout
0x01050100 10.4.0-29 ? IsTitleAllowed

These "APT:U" and "APT:S" NS services can handle launching titles/"applets", these services handle signaling for home/power button as well. Only one session for either APT service can be open at a time, normally processes close the service handle immediately once finished using the service. The commands for APT:U and APT:S are exactly the same, however certain commands are only accessible with APT:S(NS module will call svcBreak when the command isn't accessible).

Applets returning to home-menu first use commands APT:PrepareToJumpToHomeMenu and APT:JumpToHomeMenu, followed by these commands to launch home-menu: APT:PrepareToStartSystemApplet and APT:StartSystemApplet. APT:PrepareToStartSystemApplet and APT:StartSystemApplet are also used for launching the Internet Browser, the camera applet, etc.

Processes launch applications via home-menu, not directly with APT:PrepareToStartApplication and APT:StartApplication. Regular applications can't directly launch applications since APT:StartApplication launches the process without terminating the currently running application.

APT:PrepareToDoApplicationJump and APT:DoApplicationJump are used by applications, for launching native/<non-NATIVE_FIRM> applications. These commands notify Home Menu that title launching needs done, Home Menu does the actual title launching via NS commands.

AppletAttr

Bits Description
0-2 AppletPos
3 Manually Acquire/Release GPU Rights
4 Manually Acquire/Release DSP Rights
5 ?

DisplayBufferMode

Value Description
0 FORMAT_R8G8B8A8
1 FORMAT_R8G8B8
2 FORMAT_R5G6B5
3 FORMAT_R5G5B5A1
4 FORAMT_R4G4B4A4
0xFFFFFFFF FORMAT_UNIMPORTABLE

This is the same mapping as used for the GPU framebuffer color formats.

AppletPos

Value Description
-1 POS_NONE
0 POS_APP
1 POS_APPLIB
2 POS_SYS
3 POS_SYSLIB
4 POS_RESIDENT

QueryReply

Value Description
0 REPLY_REJECT
1 REPLY_ACCEPT
2 REPLY_LATER

Notification

Value Description
0 NOTIFICATION_NONE
1 NOTIFICATION_HOME_BUTTON_1
2 NOTIFICATION_HOME_BUTTON_2
3 NOTIFICATION_SLEEP_QUERY
4 NOTIFICATION_SLEEP_CANCELED_BY_OPEN
5 NOTIFICATION_SLEEP_ACCEPTED
6 NOTIFICATION_SLEEP_AWAKE
7 NOTIFICATION_SHUTDOWN
8 NOTIFICATION_POWER_BUTTON_CLICK
9 NOTIFICATION_POWER_BUTTON_CLEAR
10 NOTIFICATION_TRY_SLEEP
11 NOTIFICATION_ORDER_TO_CLOSE

Command

Value Description
0 COMMAND_NONE
1 COMMAND_WAKEUP
2 COMMAND_REQUEST
3 COMMAND_RESPONSE
4 COMMAND_EXIT
5 COMMAND_MESSAGE
6 COMMAND_HOME_BUTTON_SINGLE
7 COMMAND_HOME_BUTTON_DOUBLE
8 COMMAND_DSP_SLEEP
9 COMMAND_DSP_WAKEUP
10 COMMAND_WAKEUP_BY_EXIT
11 COMMAND_WAKEUP_BY_PAUSE
12 COMMAND_WAKEUP_BY_CANCEL
13 COMMAND_WAKEUP_BY_CANCELALL
14 COMMAND_WAKEUP_BY_POWER_BUTTON_CLICK
15 COMMAND_WAKEUP_TO_JUMP_HOME
16 COMMAND_REQUEST_FOR_SYS_APPLET
17 COMMAND_WAKEUP_TO_LAUNCH_APPLICATION

AppletPreparationState

Value Description
0 NO_PREPARATION
1 PREPARED_TO_LAUNCH_APP
2 PREPARED_TO_CLOSE_APP
3 PREPARED_TO_FORCE_TO_CLOSE_APP
4 PREPARED_TO_PRELOAD_APPLIB
5 PREPARED_TO_LAUNCH_APPLIB
6 PREPARED_TO_CLOSE_APPLIB
7 PREPARED_TO_LAUNCH_SYS
8 PREPARED_TO_CLOSE_SYS
9 PREPARED_TO_PRELOAD_SYSLIB
10 PREPARED_TO_LAUNCH_SYSLIB
11 PREPARED_TO_CLOSE_SYSLIB
12 PREPARED_TO_LAUNCH_RESIDENT
13 PREPARED_TO_LEAVE_RESIDENT
14 PREPARED_TO_DO_HOMEMENU
15 PREPARED_TO_LEAVE_HOMEMENU
16 PREPARED_TO_START_RESIDENT
17 PREPARED_TO_DO_APP_JUMP
18 PREPARED_TO_FORCE_TO_CLOSE_SYS
19 PREPARED_TO_LAUNCH_OTHER_SYS
20 PREPARED_TO_JUMP_TO_APP

StartupArgumentType

Value Description
0 STARTUP_ARGUMENT_TYPE_OTHER_APP
1 STARTUP_ARGUMENT_TYPE_RESTART
2 STARTUP_ARGUMENT_TYPE_OTHER_MEDIA

CaptureBufferInfo

Offset Size Description
0x0 0x4 u32, Size
0x4 0x1 u8, 3D (0 = not 3D, 1 = 3D)
0x5 0x3 Reserved
0x8 0x4 Main Screen Left Offset
0xC 0x4 Main Screen Right Offset
0x10 0x4 Main Screen DisplayBufferMode
0x14 0x4 Sub Screen Left Offset
0x18 0x4 Sub Screen Right Offset
0x1C 0x4 Sub Screen DisplayBufferMode

"APT:A" Service

This was added with 7.0.0-X. Official apps built with the CTRSDK for system-version >=7.0.0-X normally use the "APT:A" service instead of "APT:U". Those processes also have "APT:A" instead of "APT:U" in the service-access-control. It's unknown whether there's anything which is only accessible via "APT:A".

Applets

NS module does not verify that the input appID for the APT service cmds are correct for that type of command. For example, a process-launch of a SystemApplet via LibraryApplet commands works fine(minus the launched-process side of APT probably).

System Applets

On Old3DS there could only be one applet here(Home Menu, Internet Browser, Friend-List, etc) with programID-high 00040030 running at a time. On Old3DS when directly launching one of these 00040030 applets with Home Menu, the Home Menu process will terminate once the process is launched. On Old3DS when returning to Home Menu from that launched process, the Home Menu process is launched again.

On New3DS the Home Menu process is still running/in-memory, while another system-applet is running. On New3DS it appears that the Home Menu process is terminated+relaunched, when another system-applet terminated without exiting with APT properly.

Library Applets

Library applets can be launched by applications and regular applets. These library applets render to the screen(s) when running, etc. For example, this includes swkbd for text input. See the below appIDs in the 0x2XX range, the actual appID used is 0x4XX however.

Input data can be sent to the library applet via the NS parameter buffer, and/or with shared-memory with a shared-mem handle sent to the library applet. Output data from the library applet can be received by APT:ReceiveParameter, the library applet can also use the specified shared-mem for output too.

AppIDs

AppID Description
0x101 Home Menu (menu)
0x103 Alternate Menu
0x110 Camera applet (CtrApp)
0x112 Friends List applet (friend)
0x113 Game Notes applet (Cherry)
0x114 Internet Browser (spider/SKATER)
0x115 Instruction Manual applet
0x116 Notifications applet (newslist)
0x117 Miiverse applet (olv)
0x118 Miiverse posting applet (solv3)
0x119 Amiibo settings (cabinet)
0x201 Software Keyboard (swkbd) (?)
0x202 Mii Selector (appletEd) (?)
0x204 Photo Selector (PNOTE_AP) (?)
0x205 Sound Selector (SNOTE_AP) (?)
0x206 Error Display (error) (?)
0x207 eShop applet (mint) (?)
0x208 Circle Pad Pro Calibrator (extrapad) (?)
0x209 Notepad (memolib) (?)
0x300 Application
0x301 eShop (tiger)
0x401 Software Keyboard (swkbd)
0x402 Mii Selector (appletEd)
0x404 Photo Selector (PNOTE_AP)
0x405 Sound Selector (SNOTE_AP)
0x406 Error Display (error)
0x407 eShop applet (mint)
0x408 Circle Pad Pro Calibrator (extrapad)
0x409 Notepad (memolib)
0xF10 ProgramID: 0004003000008900.
0xF11 ProgramID: 000400000FFFFD00.
0xF12 ProgramID: 000400000FFFFC00.
0xF13 ProgramID: 000400000FFFFB00.
0xF14 ProgramID: 000400000FFFF900.
0xF15 ProgramID: 000400000FFFF800.
0xF16 ProgramID: 000400000FFFF700.
0xF17 ProgramID: 000400000FFFF600.
0xF18 ProgramID: 000400000FFFF500.

These AppIDs are all for NAND titles, except for 0x300. AppIDs in the 0x1XX range are applets(programID-high 00040030), and the AppIDs in the 0x2XX range are "system libraries"(programID-high 00040030). The 0xFXX AppID range is for development NAND applications, these are not available for retail.

Note that at some point the total AppID entry count was changed from 28 to 27.