Lot 05 · PC · In design
The counter that walks the ROM — interrupts, vectors, and the stack.
Program counter, stack pointer, multiple interrupt lines, keyboard vector tables, and scalable I/O channels—including printer support on the long tail.
Where the ALU is combinational glory, the PC board is sequencing discipline: fetch, branch, jump modes overlaid on the low bits of the 32-bit word, interrupt entry and return, and a stack pointer sheet that makes calls real. Tomato’s PC is equally robust on paper—vector tables for a keyboard, room for peripheral channels, the control fabric TomatoOS will assume at boot.
Sheets
05_program_counter.kicad_sch — PC increment, load, branch/jump muxing. stack_pointer.kicad_sch — push/pop addressing and stack discipline. Local EEPROM decode maps the universal opcode into enable lines for each path—no central microcode blob on a long ribbon cable.
- Interrupts
- Multiple · vector tables
- I/O
- Keyboard · printer · scalable channels
- Status
- In design · schematic started
- Project
hardware/kicad/boards/05_program_counter/