The Undocumented Pi
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Hardware
SoC
There is a nicely ordered table with all BCM2835_registers as found in the GPU code published by Broadcom. Unfortunately, the table does not quite match the SoC in the Raspberry Pi, but it's a good start. The sections below should serve as a companion to that table.
BCM2711
The BCM2711 does not have PLLH.
PMIC
The BCM2835 chip has an on-chip SMPS and an LDO for the LPDDR2 memory chip. RPi2 and RPi3 B use custom circuitry made of discrete components to do the power-up sequencing, including an NCP6343 chip (datasheet) at I²C address 0x1c. The RPi 3B+ and RPi 4B boards contain a MaxLinear MxL7704 (datasheet) at address 0x1d.
The PMIC is always on the system I²C bus (I2C8 on RPi4, I2C0 on all other devices).
See also this very informative blog post by James Adams.
Boot ROM
Firmware
Abbreviations
- CM
- Clock Manager
- HSM
- HDMI State Machine
- OTP
- One-Time Programmable (memory)
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