Tom's blog

A blog about some custom developments and experiences...

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Processor

D65

As a rolling stone, my debugger is always moving forward… step by step… It now comes in two flavors: a terminal app with a terminal (ala GDB), and a mac os app (ala Xcode). And has a name: D65! As… Continue Reading →

WDC 65C02: Enhanced debugger

I had an issue that made me scratching my head for a few days… I was having some bytes of memory (supposed to be ‘data’) tagged as ‘instruction’… And it was giving bad results, false positives, etc. in the resulting… Continue Reading →

WDC 65C02: Testing the result

Once the opcodes are all implemented, we need to test that the resulting “virtual processor” emulates everything correctly. We already saw previously that we can assemble some source code, feed the emulator with the resulting binary and check the disassembled… Continue Reading →

The T-800 has a 6502

Here is a frame from The Terminator movie (James Cameron, 1984) where we can see its processor sounds similar to a 6502 (but there are still some incoherences with random or just incremented numbers xD)

WDC 65C02: Memory mapper

One good idea I had recently was to implement a memory mapper. I give it an address (typically when some binary is loaded into memory) and it recursively parses all the bytes from it. When it points to an instruction,… Continue Reading →

WDC 65C02: A bit further…

I did some progress on the debugger: – it now scans for potential labels (looking for jump and branch) – then adds them to the returned disassembled code – it has a better command line tool (history, autocompletion) – it… Continue Reading →

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