УМК-80 emulator

Emulator of the УМК-80 (Учебный микропроцессорный комплект, "training microprocessor kit"), a Soviet educational trainer built by the ВЭФ association in Riga, Latvian SSR — part number РР3.059.004 (briefcase) and РР3.059.004-01 (desktop). It is a teaching machine built around the КР580ВМ80А, the Soviet clone of the Intel 8080.

It emulates the CPU cycle-accurately, the six multiplexed seven-segment displays with their real persistence, the 24-key keyboard matrix, the three rows of panel LEDs, and single-step execution both by instruction and by machine cycle.

The monitor ROM is included, reconstructed from the assembler listing in the original factory documentation. See The ROM below.

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Building

You need a C11 compiler and nothing else. The core does not even use the standard library.

Windows (primary target)

mingw32-make

The graphical frontend uses plain Win32 (user32 + gdi32), which ships with Windows itself: the .exe runs on a clean machine with no DLLs to copy. Tested with gcc 16.2 from MSYS2 (C:\msys64\mingw64\bin).

Linux and macOS

make

The graphical frontend uses SDL2 (libsdl2-dev on Debian and derivatives). Everything else — core, tools, tests and headless mode — builds with no dependencies at all.

Verified on Ubuntu 22.04 (WSL2, gcc 11, SDL2 2.0.20): builds without a single warning, passes all four acceptance checks and the ROM cross-verification, and the SDL2 window opens and responds to the keyboard. 8080EXM takes 34 s there. macOS has not been tested.

With CMake

An equivalent CMakeLists.txt is included if you prefer it:

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release && cmake --build build

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Running

Graphical panel

mingw32-make run

or directly build/umk80 --rom rom/monitor.bin.

Drive it by clicking the drawn keys, or from the host keyboard:

Host	УМК-80
0–9, A–F	hexadecimal keys
F1 … F6	П РГ СТ КС ЗК ПМ
space	parameter separator
Enter	ВП (end of directive)
Esc	СБ (reset)
Backspace	ПР (interrupt)
F8	ШГ (step)
F9	РБ/ШГ — latches single-step mode
F10	КМ/ЦК — makes each step one machine cycle

There are also two windowless modes, handy for tests and screenshots:

build/umk80 --rom rom/monitor.bin --keys "p0800.3E.AA.C3.00.08.>" --shot panel.ppm

Debugger and headless mode

umkcli is both the headless mode and the debugger:

build/umkcli --rom rom/monitor.bin                  # interactive
build/umkcli --rom rom/monitor.bin -c "run 400000" -c display

Main commands (help lists them all):

Command	What it does
load <f> [addr], loadhex <f>	load raw binary or Intel HEX
save, savehex	dump memory
run [cycles], go <addr>	run to a cycle budget or to a breakpoint
step [n], cycle [n]	step by instruction / by machine cycle
bp <addr>, bp list, bp del, bp clear	breakpoints
regs, reg <r> <v>, mem, poke, dis	inspect and edit
key <name>, keys a,b,c	press panel keys
display, panel	seven-segment and LED state
state save|load <f>	save and restore the whole machine

Standalone tools

build/umkasm program.asm program.bin        # 8080 assembler
build/umkdis program.bin --org 0x800        # disassembler
build/umkrom rom/monitor.lst rom/monitor.bin --asm rom/monitor.asm

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Checking that it works

mingw32-make test

runs the four acceptance checks:

1. CPU validation — TST8080, 8080PRE and CPUTEST. The fourth, 8080EXM, takes minutes and runs separately with make test-exm. All four pass, and 8080EXM with all 26 CRCs correct.
2. The real monitor — types the full key sequence into the authentic monitor ROM and checks that РГ + A displays A - AA.
3. Multiplexing fidelity — a program that does not blank the displays before changing the segment mask must produce ghosting; the corrected one must show a clean HELLO.
4. Single-step — one press of ШГ advances exactly one instruction with РБ/ШГ latched, and exactly one machine cycle if КМ/ЦК is latched too.

Plus make verify-rom, explained next.

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The ROM

No public dump of the УМК-80 monitor ROM exists. This one is reconstructed from the assembler listing included in the scanned factory documentation (Р.Р.00004-01 12 01-1, «Системный монитор. Текст программы», 1986, литера О_I, printed by the ISIS-II 8080/8085 MACRO ASSEMBLER V4.0).

The transcription lives in rom/monitor.lst, with the object-code column and the source column side by side, and it is verified by two independent paths that must agree:

make verify-rom
  ->  VERIFICATION OK: reassembled == OBJ column, 2048 bytes identical

• umkrom rebuilds the image from the listing's OBJ column;
• umkasm reassembles the source column.

For a transcription error to survive, it would have to be duplicated exactly in both columns. On top of that, the resulting image boots and drives the machine, which is the third check.

If you get hold of a real 1 KB ROM dump, it takes priority: load it with --rom and the core will use it as is.

Image contents (2 KB, 0000h–07FFh):

0000-03FF   Монитор            (the monitor)
0400-044B   ПРОГРАММАТОР УМК   (EPROM programmer, also in the listing)

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Machine map

0000-03FF   ПЗУ (ROM), monitor
0400-07FF   ПЗУ (ROM), second half
0800-0FFF   ОЗУ (RAM), 2 KB in the documented revision
   0FCE-0FF9   monitor variables and register table
   0FEE        interrupt vector table in RAM
   0FFA-0FFF   display refresh buffer (6 bytes)

F8   КР580ВВ55А port A — digit select and keyboard column scan
F9   КР580ВВ55А port B — segment mask
FA   КР580ВВ55А port C — keyboard rows (mask 74h)
FB   КР580ВВ55А control
FC   single-step mode (bit 0)

Two board profiles are selectable. The default is the documented revision (2 KB of RAM); --rev1 selects the earlier one, with 1 KB mirrored. The reasoning is in UNKNOWNS.md §1 and PLAN.md §1.1-bis.

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Layout

core/        core: CPU, bus, ВВ55, displays, keyboard, panel, single-step
             — freestanding C11, no libc, no pointers in the state
frontend/    graphical panel: plain Win32 on Windows, SDL2 on POSIX
cli/         headless mode and debugger
tools/       assembler, disassembler, ROM reconstructor
rom/         listing transcription, source and image of the monitor
tests/       the four acceptance checks
docs/        provenance of the documentary sources

The core contains no monitor logic and no interface logic: the ROM is pluggable and the panel is drawn outside it. umk_machine_t holds no pointers, so saving and restoring the entire machine state is a struct copy.

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Documents

• PLAN.md — the work plan, with what is documented and where every fact comes from.
• UNKNOWNS.md — everything that could not be confirmed: what is known, why it is not enough, and how it was resolved or how it could be. Read it before trusting any fine detail.
• docs/SOURCES.md — where each document comes from, with its SHA256.

Where to look

There is no public dump of this machine's ROM. The one in this repository was reconstructed by transcribing the 39 pages of ISIS-II assembler listing that come with the scanned factory documentation, by hand. The listing prints the address, the object bytes and the source of every line, which gives two independent paths to the same result: read the bytes, and reassemble the source. They have to agree, and that is what makes the reconstruction checkable rather than a guess.

So if you want to verify this ROM, or to build one for a sibling machine, the place to look is that scanned documentation, not a ROM archive.

License and provenance

The emulator — core, frontend, debugger, tools and tests — is original work and is released under the GNU General Public License v3.0. Contributions require the agreement in CLA.md; see CONTRIBUTING.md.

The rom/ directory is outside that license. It holds the machine's monitor, transcribed from the 1986 factory listing: Soviet documentation whose corporate author no longer exists and over which the publisher of this repository holds no rights, and therefore cannot sublicense. It is included for preservation and interoperability — without the monitor the emulator does not boot, and no public ROM dump exists — kept separate from the core and replaceable by any other image via --rom. Details in rom/PROVENANCE.md.

The panel is drawn from scratch using the manufacturer's own drawing (Рис. 2 of the ПС). The photographs in docs/ref/, used for the palette and the proportions, belong to their authors and are not part of this repository nor of what it distributes.