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Software Development Guide

This guide explains how to write, compile, and run different software on the Mach-V processor.

Software Directory Structure

The sw/ directory is organized by application. For example:

  • sw/coremark/ contains the CoreMark benchmark source code and build scripts.

Toolchain Setup

I used the RISC-V GNU Toolchain to compile C code into machine code (hex files) and then load them into the Mach-V processor's IROM (AA_IROM.mem) and DMEM (AA_DMEM.mem).

Install Toolchain

The toolchain that I used is pre-built and can be found on GitHub. I chose the rv32i-131023 version. The installation guide is also available on the repository.

Build Configuration

To compile C code into hex files for IROM and DMEM, I used three files: Makefile, ld.script and crt.s. For every C program that is newly written, these three files need to be added and modified accordingly.

Makefile

Makefile defines the rules for the make command to work. Make sure the GCC_DIR is correct and feel free to change the CFLAGS as you wish (like changing the Optimization flag from -O2 to -O3 etc).

Info

You can get a template from any one of the application, but I recommend the sw/calculator/Makefile.

ld.script

ld.script first specifies the size left for IROM and DMEM. In the Mach-V processor,

  • ROM stands for IROM, its ORIGIN is 0x00400000, its LENGTH depends on the size of the code.hex generated.
  • RAM stands for DMEM, its ORIGIN is 0x10010000, its LENGTH depends on the size of the data.hex generated.

Secondly, it specifies which section in the compiled program goes to which memory region. This determines which part of the program is stored in IROM and which part is stored in DMEM. For example,

  • the .rodata and .data sections are dumped into DMEM
  • the .text section is dumped into IROM.

crt.s

The crt.s file is the entry point of the software. It sets up the execution environment before handing control to the C main() function.

For each new application, the li sp, <address> instruction needs to be modified to set the stack pointer (sp) to the top of DMEM. The stack grows downwards from high memory to low memory. Thus you should set the stack pointer to the very end of your available DMEM.

\[ \text{Initial SP} = \text{DMEM_BASE} + \text{DMEM_SIZE} \]

For example, if your DMEM size is 7KB (the sw/coremark example), and the Mach-V processor's DMEM base address is 0x10010000, then the initial stack pointer should be set to:

li sp, 0x10011C00  # 0x10010000 + 7 * 1024

Compile and Load

After setting up the three files above, you can simply run the make command in the terminal while being in the application's directory. If everything is set up correctly, two hex files named code.hex and data.hex will be generated. Copy and paste the contents of code.hex into AA_IROM.mem and data.hex into AA_DMEM.mem in the Vivado project to load the program into the Mach-V processor.

To clean up the generated files, you can run make clean.

Success

Now you are ready to write, compile, and run your software on the Mach-V processor! Feel free to move on to explore the existing software applications in the sw/ directory.