Lot 04 · Register · In design

256 names, three reads, one write — the monstrous GPR file.

Tomato’s register board implements a 3-read-1-write file expanded to 256 general-purpose registers, plus the instruction register sheet that holds the 32-bit word the rest of the machine decodes.

KiCad · 04_register · eight banks on the word

The 32-bit instruction word carries five register fields—rd, rA, rB, rC, and a 3-bit bank—so the physical file must serve three concurrent read ports and one write port without turning the PCB into a fire hazard. Digital already models the behaviour; the board work is fanout, tri-state discipline, and decode EEPROMs sitting next to the storage arrays.

Sheets

register.kicad_sch — GPR arrays and read/write port muxing. ir.kicad_sch — instruction register latch and hold timing relative to fetch. Decode stays local: universal 10-bit opcode into combinational EEPROM, same pattern as every other slice in the stack.

GPRs: 256 · 3R1W
Banks: 8 · via 3-bit bank field
Status: In design · schematic started
Project: hardware/kicad/boards/04_register/