Information gathered from iaudio X5 OF disassembly

Preloader

General Info

This part of firmware resides from 0x00000000 to 0x00010000 and never changes. It is a single-threaded program that handles the following tasks:

1. Device initialization.
2. USB HDD mode.
3. Adapter/USB charge mode.
4. Firmware upgrade.
5. Executing the actual firmware (i.e., jmp 0x10000).

General Code Flow

• Initialization steps 1 & 2
• If USB and/or AC adapter is connected, go to Initialization step 3; otherwise, go to Initialization step 4.

Initialization, step 1

• Internal ColdFire registers: sp, vbr, cacr, acr0, acr1, mbar, mbar2, rambar0, rambar1
• Various registers on MBAR and MBAR2 (interrupts, timers, DMA, IIS_CONFIGs, EBU_CONFIGs)
• GPIO out/enable/function registers

  	OUT	ENABLE	FUNCTION
  GPIO	0x40200018	0x60A0E018	0x6FA1E179
  GPIO1	0x4830	0x483C	0x483C

• DRAM controller
• PLL_CONFIG (to 0x11436059)
• Chip Select 0
• Copy rest of preloader to DRAM

Initialization, step 2

• UART0
• LCD
• I2C controller (interface 1 only)
• PCF50606
• CY7C68310

Initialization, step 3 (USB and/or AC adapter connected)

• Remote LCD detect & init
• Turn of backlight and display boot screen
• If USB is connected:
  • ATA init & reset
  • HDD identify & init
  • Partition table & FAT32 init
  • Set slow CPU freq (PLL_CONFIG = 0x10422035) and adjust UART divider (32)
  • Enter ATA bridge mode
• If AC adapter is connected:
  • ATA init & reset
  • HDD identify & init
  • Partition table & FAT32 init

Initialization, step 4 (neither USB nor AC adapter connected)

• ATA init & reset
• Jump to firmware (at 0x10000)

To be continued...

Firmware

General Info

This part of firmware resides from 0x00010000 to ~0x019D0000 and can be upgraded.

It has two parts:

• the first is composed of ~18 data and/or code segments, most of which are cached to IRAM/DRAM.
• the second contains read-only data (images, remote images, text strings, ...) and begins at 0x01700000. H3Mod changes things here.

To be continued...