Changes

== General ==

== General ==

Just like the Wii and the GameCube, the Wii U contains a dedicated chip for the Real-Time Clock (RTC).

Just like the Wii and the GameCube, the Wii U contains a dedicated chip for the Real-Time Clock (RTC).

The MX23L0002 is a custom chip that encompasses the RTC and a small SRAM bank. While the chip still sits on the EXI bus (channel 0, device 1) it no longer contains the GameCube font sets, as this data is now handled on the software side.

The MX23L0002 is a custom chip that encompasses the RTC and a small SRAM bank. While the chip still sits on the [[Hardware/Legacy#External_Interface|EXI bus]] (channel 0, device 1) it no longer contains the GameCube font sets, as this data is now handled on the software side.

 

On a regular retail Wii U, this is the only device registered on the EXI bus. An additional device called NESCAFE (part of the debug CORTADO package) was presumably used in the past for debugging purposes and used to sit on channel 0 as device 2.

== Communication ==

== Communication ==

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| RTC_SRAM || 0x20000100 || Battery backed memory

| RTC_SRAM || 0x20000100 || Battery backed memory

  The SRAM has a total size of 64 bytes, starting at offset 0x20000100

  The SRAM has a total size of 64 bytes, starting at offset 0x20000100 and ending at offset 0x20001000.

and ending at offset 0x20001000.

  Therefore, each word is located at (0x20000100 + 0x100 * i) with (i < 0x10).

  Each word is located at (0x20000100 + 0x100 * i) with (i < 0x10).

On Wii U mode (recent firmware versions only), this memory is used to store IOSU kernel panic strings.

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| RTC_SNAPSHOT || 0x20400000 || Contains a snapshot of RTC_COUNTER (taken upon power on?)

| RTC_SNAPSHOT || 0x20400000 || Contains a snapshot of RTC_COUNTER (taken upon power on?)

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|-

| ONTMR_SET || 0x21000000 || Contains the value set for the ON timer

| ONTMR_SET || 0x21000000 || Contains the value set for the ON timer

|-

|-

| OFFTMR_SET || 0x21000100 || Contains the value set for the OFF timer

| OFFTMR_SET || 0x21000100 || Contains the value set for the OFF timer

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| RTC_UNK0 || 0x21000400 || Always 0x03030303 after power on (PLL?)

| RTC_UNK0 || 0x21000400 || Always 0x03030303 after power on (PLL?)

|-

|-

| RTC_CONTROL0 || 0x21000C00 || RTC control register 0

| RTC_CONTROL0 || 0x21000C00 || RTC control register 0

  The last byte stored here is always RTC_REVISION (0x00 or 0x01).

  The last byte stored here (mask == 0x000000FF) is always RTC_REVISION (0x00 or 0x01).

  The following flags can be set here:

  The following flags can be set here:

  0x04000000 [POFFLG_FPOFF]: Set upon a forced power off.

  0x04000000 (POFFLG_FPOFF): Set upon a forced power off.

  0x02000000 [POFFLG_4S]: Set upon a 4 second power button press.

  0x02000000 (POFFLG_4S): Set upon a 4 second power button press.

  0x01000000 [POFFLG_TMR]: Set upon a OFF timer power off.

  0x01000000 (POFFLG_TMR): Set upon a OFF timer power off.

  0x00010000 [PONLG_TMR]: Set upon a ON timer power on.

  0x00010000 (PONLG_TMR): Set upon a ON timer power on.

  0x00020000 [PONFLG_SYS]: Set upon a system power event.

  0x00020000 (PONFLG_SYS): Set upon a system power event.

  0x00000800 [UNSTBL_PWR]: Unknown. boot0 checks this before launching a recovery boot1 image.

  0x00000800 (UNSTBL_PWR): Unknown. boot0 checks this before launching a recovery boot1 image.

  0x00000200 [LOW_BATT]: Set when the CMOS battery is worn off.

  0x00000200 (LOW_BATT): Set when the CMOS battery is worn off.

  0x00000100 [CANARY]: Unknown. Likely set on factory for testing.

  0x00000100 (CANARY): Unknown. Likely set on factory for testing.

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| RTC_CONTROL1 || 0x21000D00 || RTC control register 1

| RTC_CONTROL1 || 0x21000D00 || RTC control register 1

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