Difference between revisions of "Unit BootRPi"

Revision as of 03:15, 19 June 2021

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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'];

procedure Vectors; assembler; nostackframe;

procedure StartupHandler; assembler; nostackframe;

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