firmware

u6502 - Firmware

This directory contains the various programs, libraries, and utilities used by the u6502 SBC.

Build Process

Currently, all programs for the u6502 are assembled using the ca65 macro assembler which is a part of the cc65 C Compiler project. ROMs are built in the following two step process:

1. Assembly - ca65 -vvv --cpu 6502 -l {listingFilePath} -o {outputObjectFilePath} {sourceFilePath}
2. Linking - ld65 -o {outputBinaryPath} -C {linkerConfigFilePath} "{objectFilePath}"
3. Flashing - The output from the linker is a binary that can be burned to the EEPROM (U3). This binary should work with any number of EEPROM programers, but I have only tested it with Xgpro.

A simple PowerShell script build.ps1 is used to automate the build process in a Windows build environment. Usage of this script requires that the cc65 binaries be in the PATH environment variable. When using this script all output will go into the build directory.

Linker Configuration

The cc65 linker (ld65) uses a configuration file to properly layout all of the assembled sources into a single output binary. I don't fully understand the syntax and capabilities of this configuration tool, but the documentation is fairly good. In the case of the u6502, roms/common/memmap.cfg is the linker configuration. Of most importance here are the MEMORY and SEGMENTS sections which define the system's memory map and correlate any segments used in the assembly files with the correct memory locations.