Configuration & Memory Map Basics

This tutorial covers the essential CPU configuration settings needed to get started with the test framework. You’ll learn the basic structure of configuration files and the minimum required settings.

Basic Configuration

CPU configurations are defined in JSON files with three essential components:

{
    "reset_pc": "0x8000_0000",
    "mmap": {
        "dram": {
            "main_ram": {"address": "0x8000_0000", "size": "0x40_0000_0000"}
        },
        "io": {
            "uart": {"address": "0x1000_0000", "size": "0x1000"},
            "timer": {"address": "0x1001_0000", "size": "0x1000"}
        }
    }
}

Required Settings

reset_pc

The program counter value when the processor starts. Typically set to 0x8000_0000 for RISC-V systems.

mmap.dram

Memory map defining at least one DRAM region where programs and data are stored. Each region needs:

address: Starting memory address
size: Size of the memory region

Memory Map Structure

The memory map has two main sections:

DRAM (Required): Main system memory. Must include at least one region:

"dram": {
    "main_ram": {"address": "0x8000_0000", "size": "0x40_0000_0000"}
}

IO (Optional): Memory-mapped peripherals:

"io": {
    "uart": {"address": "0x1000_0000", "size": "0x1000"},
    "timer": {"address": "0x1001_0000", "size": "0x1000"}

}

Address Format

Addresses can be written as:

Hex strings with underscores: "0x8000_0000"
Plain hex strings: "0x80000000"
Integers: 2147483648

Using Configuration in Tests

Load your configuration file on the command-line with the --cpuconfig flag:

--cpuconfig my_config.json

Configuration Templates

Minimal Configuration

{
    "reset_pc": "0x8000_0000",
    "mmap": {
        "dram": {
            "ram": {"address": "0x8000_0000", "size": "0x8000_0000"}
        }
    }
}

Validation and Debugging

Common errors to avoid:

Missing dram section in memory map
Invalid address formats (must include 0x prefix for hex)
Empty configuration sections

If your configuration fails to load, check that all required fields are present and addresses are properly formatted.

Advanced Configuration

For more complex configurations including secure memory, test generation parameters, and extensive RISC-V feature sets, see the Configuration Schema Reference.