From The Apple Wiki

This should help people reversing iBoot and friends. It is a work in progress.


Base: 0x38000000

Register Description
0x00 Configuration
0x04 Setup
0x20 through 0x30 Output SHA1 hash
0x40 through 0x7C Data Input (64 Bytes)

See S5L8720 SHA1 for a more detailed description

DMA (PL080)[edit]

This appears to use an ARM PrimeCell PL080. You can read the technical reference manual here[dead link].

Base (dmac0): 0x38200000
Base (dmac1): 0x39900000

Register Description
0x0 Interrupt Status
0x4 TC Status (If HIGH, transaction complete)
0x8 TC Interrupt Clear
0xC Error Interrupt Status
0x10 Error Interrupt Clear
0x14 TC Interrupt Status Before Masking (Raw)
0x18 Error Interrupt Status Before Masking (Raw)
0x1C DMA Channels Enabled
0x30 Controller Configuration
0x34 Enable / Disable Synchronization
0x100 Channel 0 Source Address
0x104 Channel 0 Destination Address
0x108 Channel 0 Linked List Address
0x10C Channel 0 Control 1
0x110 Channel 0 Control 2
0x114 Channel 0 Configuration

VIC (PL192)[edit]

This appears to use an ARM PrimeCell PL192. You can read the technical reference manual here.

Base (vic0): 0x38E00000
Base (vic1): 0x38E01000

Register Description
0x0 IRQ Status
0x4 FIQ Status
0x8 Raw Interrupt Status
0xC Interrupt Select (0=IRQ, 1=FIQ)
0x10 Interrupt Enable (0=Disabled, 1=Enabled)
0x14 Interrupt Enable Clear (Write-Only; 0=No Effect, 1=Interrupt enabled with previous reg disabled)
0x18 Software Interrupt (0=Disabled, 1=Enabled)
0x1C Software Interrupt Clear (Write-Only; 0=No Effect, 1=Interrupt enabled with previous reg disabled)
0x20 Register Protection Mode. If bit 0 is set to 1, then Protection Mode is on and only privileged mode writes will work.
0x24 Software Interrupt Priority Mask (0=Masked, 1=Not Masked)
0x100 Vector Addresses
0x200 Vector Priority Levels
0xFE0 through 0xFEC Peripheral Identification Registers
  • Part Number: Bits 7 through 0 of register 0xFE0 is one portion of the part number (0x92), then bits 3 through 0 of register 0xFE4 is the other portion of it (0x1). If you do some annoying shifting, to put it together, you get 0x192 (0x92|0x11<<8&0xFFF==0x192). 0x192 indicates that it is an ARM PrimeCell PL192.
  • Designer: Bits 7 through 4 of register 0xFE4 is one portion of the designer tag (0x1), then bits 3 through 0 of register 0xFE8 is the other portion of it (0x4). Like above, we can do (0x11 | 0x4<<4) and we get 0x41, which is "A" in ASCII, meaning it was designed by ARM Limited.
  • Revision Number: Unlike the above two, this one is pretty easy. Bits 7 through 4 of register 0xFE8 is the revision number, which is "0" at least for the iPod touch 2G.
  • Configuration: The reference manual simply states that bits 7 through 2 should read back as 0, and nothing more about them. It also states that bits 1 through 0 indicate the number of interrupts supported, which appear to be 32 for the iPod touch 2G (0b00=32 Supported, 0b01=64 Supported, 0b10=128 Supported, 0b11=256 Supported).
0xFF0 through 0xFFC PrimeCell Identification Registers
  • Register 0xFF0: Should read as 0x0D
  • Register 0xFF4: Should read as 0xF0
  • Register 0xFF8: Should read as 0x05
  • Register 0xFFC: Should read as 0xB1


All information here was gathered by reversing iBoot and friends.

Base: 0x3D100000

Register Description
0x0 Unused & Unreferenced Register
0x4 Not yet documented
0x8 Chip Info
  • Chip ID: Bits 31 through 16 (0x8720, meaning it is an S5L8720)
  • Security Epoch: Bits 15 through 1 (0x01)

WDT (Watchdog Timer)[edit]

Base: 0x3C800000

Register Description
0x0 Control Register

NOTE: It seems that you can disable Watchdog Timer by rewriting this register to 0x00000000, and you can reboot the device by rewriting it to 0x100000

0x4 Watchdog Timeout Duration
0xC Interrupt Clear


See separate article S5L8720 Timers (Hardware)

ARM7 (Second CPU)[edit]

All information here was gathered by looking at the code for the ARM7 Go command, as well as noting that although 2.1.1 iBoots reference this as 0xB8600000, 0x80000000 through 0xFFFFFFFF is mapped to 0x0 through 0x7FFFFFFF when the MMU does it's stuff.

Base: 0x38600000

Register Description
0x100 Running Status

To halt the ARM7: Clear all bits then set bit to 2. To make it resume: Set bit 1

0x110 Code Address

To run code, halt the ARM7, write the load address of the code to this register, write 0x3FF0000 to register 0x114, then resume the ARM7

0x114 "Code Waiting"

I don't know exactly what this register does, but I named it like this because 0x3FF0000 is written to this register when there is a load address of code to be jumped to in register 0x110


Base (uart0 - Serial): 0x3CC00000
Base (uart1 - Bluetooth): 0x3DB00000
Base (uart2): 0x3DC00000
Base (uart3): 0x3DD00000

Register Description


Base (spi0 - NOR Flash): 0x3C300000
Base (spi1 - NOR Flash): 0x3CE00000
Base (spi2): 0x3D200000
Base (spi3): 0x3DA00000
Base (spi4 - Multi Touch): 0x3E100000

Register Description