Hardware/eFuse

eFuse
Latte Registers
Access
Espresso	None
Starbuck	Full
Registers
Base	0x0d8001ec
Length	0x8
Access size	32 bits
Byte order	Big Endian

General

The One Time Programmable memory is programmed sometime during the factory process and can never be changed afterwards. The Wii U's OTP is much larger than the Wii's (1KB split across 8 banks of 128 bytes each) and contains an assortment of read-only data, including the console's encryption/decryption keys.

Register List

Latte GPIOs
Address	Bits	Name	Description
0x0d8001ec	32	HW_OTP_COMMAND	OTP command
0x0d8001f0	32	HW_OTP_DATA	OTP data

General Registers

HW_OTP_COMMAND (0x0d8001ec)
	31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16
Access	R/W	U
Field	RD
	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Access	U					R/W
Field						ADDR

Field	Description
RD	Set to one to execute a read command. If clear, then the data in HW_OTP_DATA is unchanged.
ADDR	Word address to read. 0x00 to 0x1F (32 4byte words) ORed with the bank's number (0x000 to 0x700).

This register contains the command sent to the OTP. It is unknown whether is register is also used during the factory process to program the OTP.

---

HW_OTP_DATA (0x0d8001f0)
	310
Access	R

This register contains the output data for the last issued OTP read command. The execution of a read operation via the HW_OTP_COMMAND register immediately changes this register without any delay.

IOSU

The Wii U's IOSU interacts with the OTP by setting it's respective Latte registers. In addition to this, the IOS-CRYPTO process is also able to access the OTP indirectly through syscall 0x22, which takes the OTP word index, a buffer to store the result and the requested size as parameters. The IOS-KERNEL then converts the word index:

int read_otp_internal(int index, void* out_buf, u32 size)
{
  generate_control_bits();
  
  if (size != 0)
  {
    int step = 0;
    
    while (step < size)
    {
      int word_addr = index + (step >> 2);
      int word_offset = word_addr & 0x1F;      // Each OTP bank has 0x20 * 4 = 0x80 bytes. Valid word indexes go from 0x00 to 0x1F.
      word_addr = word_addr << 3;
      word_offset = word_offset | 0x80000000;  // Set OTP read flag.
      word_addr = word_addr & 0x700;           // OTP bank goes from 0x000 to 0x700.
      word_addr = word_addr | word_offset;
      
      *(u32*)0x0D8001EC = word_addr;                     // HW_OTPCMD
       
       // Keep checking the read flag.
       if (!((*(u32*)0x0D8001EC) & 0x80000000))
         break;
      
      *(u32*)(out_buf + step) = *(u32*)0x0D8001F0;       // HW_OTPDATA
      
      step += 4;	
    }
  }
  
  generate_control_bits();
  return 0;
}

syscall_0x22(index, out_buf, size)
{
  // Do some permission checks.
  ...
  
  // Internal IOS-KERNEL function.
  read_otp_internal(index, out_buf, size);
}

OTP Contents

The following things are stored inside the OTP and requested by the IOSU kernel at some point:

Bank	Address	Size	Description
0 (vWii bank)	0x005 to 0x009	0x10 bytes	Possibly old Wii key.
0 (vWii bank)	0x011 to 0x016	0x14 bytes	Possibly old Wii hash.
0 (vWii bank)	0x016 to 0x01A	0x10 bytes	Possibly old Wii key.
1 (unknown)	0x100 to 0x101	0x04 bytes	Unknown. Syscall 0x20 checks this value.
1 (unknown)	0x104 to 0x108	0x10 bytes	Unknown.
1 (unknown)	0x108 to 0x10C	0x10 bytes	Unknown.
1 (unknown)	0x114 to 0x118	0x10 bytes	Unknown.
1 (unknown)	0x118 to 0x11C	0x10 bytes	Unknown.
2 (unknown)	0x208 to 0x20C	0x10 bytes	Unknown.
2 (unknown)	0x20C to 0x210	0x10 bytes	Unknown.
2 (unknown)	0x210 to 0x214	0x10 bytes	Unknown.
2 (unknown)	0x214 to 0x218	0x10 bytes	Unknown.
2 (unknown)	0x218 to 0x21C	0x10 bytes	Unknown.
2 (unknown)	0x21C to 0x300	0x10 bytes	Unknown.
3 (unknown)	0x300 to 0x304	0x04 bytes	Unknown.
3 (unknown)	0x304 to 0x308	0x10 bytes	Unknown.
3 (unknown)	0x308 to 0x30C	0x10 bytes	Unknown.
3 (unknown)	0x318 to 0x31D	0x14 bytes	Unknown.
4 (unknown)	0x407 to 0x408	0x04 bytes	Unknown.
4 (unknown)	0x408 to 0x410	0x20 bytes	Unknown.
4 (unknown)	0x410 to 0x418	0x20 bytes	Unknown.
4 (unknown)	0x418 to 0x41C	0x10 bytes	Unknown.
5 (unknown)	0x500 to 0x501	0x04 bytes	Unknown.
5 (unknown)	0x501 to 0x502	0x04 bytes	Unknown.
5 (unknown)	0x502 to 0x503	0x04 bytes	Unknown.
5 (unknown)	0x503 to 0x513	0x40 bytes	Unknown.
6 (SEEPROM bank)	0x600 to 0x618	0x60 bytes	Possibly the old SEEPROM certificate data.
6 (SEEPROM bank)	0x618 to 0x700	0x20 bytes	Unknown.
7 (unknown)	0x700 to 0x800	0x80 bytes	Unknown. Doesn't seem to be used.