Unit BootRPi

Return to Unit Reference

Description

---

Ultibo Initialization code for Raspberry Pi unit

Raspberry Pi

SoC: Broadcom BCM2835

CPU: ARM1176 (ARMv6) (1 @ 700MHz)

Cache: L1 16KB / L2 128KB (Shared with GPU)

FPU: VFPV2

GPU: Broadcom VideoCore IV (VC4)

RAM: 512MB (256MB on Model A/A+)

USB: Synopsys DesignWare Hi-Speed USB 2.0 On-The-Go Controller (DWCOTG)

LAN: SMSC LAN9512 (SMSC LAN9514 on Model B+ / No LAN on Model A/A+/Zero) (SMSC95XX)

SD/MMC: Arasan (BCM2708)

WiFi: (None)

Bluetooth: (None)

Other: GPIO / SPI / I2C / I2S / PL011 (UART) / PWM / SMI / Watchdog (PM) / Random (RNG) / Timer ???

Boot RPi

The boot loader on the Raspberry Pi will load this code at address 0x00008000 onwards and set the following registers before jumping to this code.

R0 - Zero

R1 - Machine Type (Raspberry Pi or BCM2708 = 0x0c42)

R2 - Address of the ARM Tags structure (Normally 0x0100)

On entry to this code the processor will be in the following state:

World - Secure

Mode - Supervisor (ARM_MODE_SVC)

MMU - Disabled

FPU - Disabled

L1 Data Cache - Disabled

L1 Instruction Cache - Disabled

Branch Predication - Disabled

Unaligned Data Access - Disabled

Ultibo switches the processor to System mode for all operations and remains in the Secure world.

The initialization process enables the MMU, FPU, L1 Cache and other performance optimizations.

Constants

---

None defined

Type definitions

---

None defined

Public variables

---

None defined

Function declarations

---

Boot functions

procedure Startup; assembler; nostackframe; [public, alias: '_START'];

Description: Entry point of Ultibo on Raspberry Pi, this will be the very first byte executed and will be loaded by the GPU at address 0x00008000

Note	None documented

procedure Vectors; assembler; nostackframe;

Description: ARM exception vector table which is copied to address 0 by the StartupHandler

Note	See A2.6 "Exceptions" of the ARM Architecture Reference Manual

procedure StartupHandler; assembler; nostackframe;

Description: Startup handler routine executed to start the Ultibo kernel

Note	None documented

Return to Unit Reference