MOD68

Modular 16bit retro computers using cheap 4-layer 100x100mm PCBs

photondreams

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100x100mm 4 layer PCBs can be made cheaply with special offers from PCB houses.

Let's take advantage of that to experiment with a variety of interesting components for larger 68k projects.

So that we can also experiment with programmable logic, let's make the expansion connector compatible with the old Altera UP1/UP2 development kits, allowing us to interface with 5V FPGAs and CPLDs from the late 90s.

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Ready to begin OS development
photondreams • 11 hours ago • 0 comments

MOD68 is alive and kicking and ready to start development on what will eventually morph into Amagaki OS once I figure out how all the new chips work and assemble the larger board.

For now, on MOD68 we have :
- A bootloader with interrupt-driven UART that accepts programs using XMODEM-1K (with CRC)
- A loadable firmware updater that also accepts a new firmware image using XMODEM-1K and writes to flash
- A GDB remote serial protocol handler active on UART channel B, with source-correlation, tracing and breakpoint support
- Full integration of debugging in vscode
- MOD68-LA, a logic analyzer interposer board that provides 64 signals to the logic analyzer while replicating the expansion connector. This lets me capture and view all bus activity in real time.
- A 10ms system tick timer using the UART's timer
- A 100 page draft of the OS design document

Time to get coding!