Memory Map and Boot Flow

Memory Map

The following image shows the memory map of Atom-based SoCs.

The column C shows the memory map template for all RISC-V Atom based SoCs. Column D and E show the memory map for AtomBones and HydrogenSoC respectively.

Boot Flow

Upon reset, the core jumps to the reset vector (default: 0x10000) which points to the start of BootROM. RISC-V Atom BootROM includes a stage-0 bootloader that is automatically built and included when building the AtomSim or running FPGA builds. The stage-0 bootloader uses RAM for stack. It initializes the platform, loads the user program in RAM and finally transfers control to the user program. The user program often includes a stage-1 bootloader which sets up the runtime environment and standard library before executing the application.

digraph G { rankdir=LR; reset_vec [label="Reset Vector", shape=rect, style=filled, fillcolor=white]; subgraph cluster_0 { style=filled; fillcolor=gray; label="BootROM"; stage0_bl [label="Stage-0\nBootloader", shape=rect, style=filled, fillcolor=yellow]; } subgraph cluster_1 { style=filled; fillcolor=gray; label="RAM"; stage1_bl [label="Stage-1\nBootloader", shape=rect, style=filled, fillcolor=orange]; prog [shape=rect, label="User Program", style=filled, fillcolor=cyan]; stage1_bl -> prog [label="launch"]; } reset_vec -> stage0_bl; stage0_bl -> stage1_bl; }

To know more about the stage-0 bootloader, see this page.