Add remaining illegal opcodes and tests#127
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omarandlorraine merged 3 commits intomre:illegalfrom Jan 27, 2026
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January 26, 2026 08:02
The illegal opcodes implementation caused README doc tests to hang: 1. First example used 0xff as program terminator - Previously 0xff was unimplemented (returned None), stopping execution - Now 0xff is ISC (INC+SBC) AbsoluteX, causing infinite loop - Fix: Use 0x02 (JAM) which explicitly halts the CPU 2. Second example loads euclid.bin which uses BRK (0x00) to terminate - BRK jumps to IRQ vector at $FFFE/$FFFF - Uninitialized memory contains 0x00, jumping to address $0000 - This causes infinite loop executing whatever is in low memory - Fix: Mark as no_run since it depends on external file anyway
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I have one concern and that is that the README test seems to be disabled. Can you shed light on this? I remember you ran into trouble with it, but did you get it running and passing in the end? |
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Jan 27, 2026
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Thanks, this is perfect
- Replace BRK with JAM ($02) to halt CPU after illegal opcodes impl - Fix assembly label structure (algo/algo_ were dead infinite loops) - Simplify linker.cfg to output raw binary at $0010 (was 64KB image) - Enable README doc test (remove no_run marker) The old linker config produced a 64KB memory image with code at $0400, but README loaded at $0010 causing address mismatch. New config outputs only the code segment at the correct load address.
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So that's been merged into my branch |
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Completion of #126 by @omarandlorraine. Fixes #125. Note that this targets the
illegalbranch and should ultimately be merged into main if accepted.