# PlasmaNew — reverse-engineering the real cockpit plasma display

Working notes and reference material for the cockpit plasma display.

**End goal: a hardware replica.** The original Babcock plasma panels are
starting to fail and are effectively irreplaceable. The plan is to drive a
modern **128 × 32 LED array** with a **modern microcontroller** that reads
the same RS-232 serial bus and speaks the same command protocol as the
original PD01D221 — a drop-in replacement, functionally identical from the
host's side, with none of the plasma physics or high voltage.

[vPLASMA](../src/VPlasma.App/) (the C# app in this repo) is the software
counterpart and serves the replica directly: it is an **executable
specification** of the display's behavior and a **test oracle**. Every
command semantic pinned down in `VPlasmaDevice` ports straight to the
replica's firmware, and the same differential-test rig (real panel vs.
vPLASMA) validates the replica. vPLASMA today is built from *observed
traffic* (the game's driver + a factory test tool); grounding it in the
*actual hardware* — protocol, fonts, and timing — feeds both the emulator
and the replacement firmware.

## What the display is

A **commercial off-the-shelf Babcock Display Products Division PD01D221** —
"128 × 32 dot-matrix, gas-plasma display with controller and DC-DC
converter," with an RS-232C serial interface and a dedicated microprocessor
for refresh and the user interface. Built by **Cherry** (PCB assembly
**4317-C**, Made in Taiwan, © 1994). See [`PD01D221.pdf`](PD01D221.pdf)
(Babcock doc 9200-0109 Rev A).

Product family (the suffix letter = how much is on the board):

| Model | Contents |
|-------|----------|
| PD01**B**22B | 128×32 panel + driver electronics only (host refreshes it) |
| PD01**F**221 | + on-board DC-DC converter |
| PD01**D**221 | **+ controller: RS-232C, dedicated microprocessor** ← this unit |

**VWE used it stock — no custom fonts or bitmaps were installed.** So the
display's behavior is entirely the standard Babcock PD-series firmware, and
the `ESC P` "graphics" the game drew were rendered at runtime by the game,
not preloaded. Nothing on the display is VWE-specific.

## Board inventory

Chip IDs read from the photos below.

| Ref | Part | Role |
|-----|------|------|
| U1 | **Motorola MC68HC11D0** (44-pin QFP, mask 1C17F, wk 28/94) | ROMless HC11 MCU — the controller. Runs from external bus in expanded mode. |
| U3 | **TI TMS27PC512** (PLCC-32, −150 ns, Singapore) | **64 KB OTP EPROM = the firmware** (stock Babcock code + fonts). Standard 27C512. |
| U2 | QFP ~100-pin, label **"35GWP004 REV A 3994"** | Custom Cherry display/scan **ASIC** (wk 39/94). Drives the HV stage. *Not* the firmware. |
| U4 | **Mosel MS62256L-10** | 32 KB SRAM — frame buffer / scratch. |
| U7 | **Supertex HV7708** | 32-channel high-voltage plasma driver (more HV off-frame). |
| U5 | **Maxim MAX202CWE** | RS-232 transceiver — the serial interface. |
| — | **MAX707** | Reset / watchdog supervisor. |
| Y1 | **7.3728 MHz** crystal | E-clock = 1.8432 MHz; gives exact standard baud rates. |

Memory picture: ROMless HC11 + external 64 KB EPROM (code + fonts) + 32 KB
SRAM + custom scan ASIC + HV drivers. A 64 KB program EPROM for a 128×32
panel implies far more feature set than the game ever used.

## Reference photos

| File | Shows |
|------|-------|
| [`mpul-2026-07-07-152834.jpeg`](mpul-2026-07-07-152834.jpeg) | Controller overview: MC68HC11D0 (U1), the "35GWP004" ASIC (U2), HV7708 (U7), MAX202, MAX707. |
| [`silkscreenl-2026-07-07-152841.jpeg`](silkscreenl-2026-07-07-152841.jpeg) | Cherry silkscreen: PCB **4317-C**, © 1994, "Made in Taiwan". |
| [`unknown-2026-07-07-153818.jpeg`](unknown-2026-07-07-153818.jpeg) | The **TMS27PC512 EPROM** (U3, initially unidentified), Mosel SRAM (U4), HC11. |
| [`jumpers-2026-07-07-163733.jpeg`](jumpers-2026-07-07-163733.jpeg) | The **JP1** config header next to the HC11. |

## Datasheet-confirmed facts (`PD01D221.pdf`, doc 9200-0109 Rev A)

- Serial format **8N1**, baud **jumper-selectable 4800 / 9600 / 19.2K /
  38.4K** (the game uses 9600).
- "Choice of standard fonts and styles" (= `ESC K` / `ESC H`); "program
  custom characters" (a custom-char download command — **exists but VWE
  didn't use it**); "graphic input commands / overlays" (= `ESC P`).
- Serial is **bidirectional**. Connector **J1**: pin 2 TxD (display→host),
  pin 3 RxD (host→display), pin 4 CTS, pin 8 DTR ("display ready"), pin 5
  GND. The game drove it write-only (flow control disabled, TxD ignored),
  so vPLASMA's listen-only model is faithful.
- Also carries an 8-bit **parallel** port (J2), unused by the game.
- **The datasheet does *not* contain the `ESC` command table.** That's a
  separate Babcock programming/user manual, which is **not available online**
  (checked general web, datasheetarchive, bitsavers, archive.org, resellers;
  only this datasheet was ever digitized). Sources for it: ask Babcock
  directly (La Mirada CA, (714) 994-6500, babcockinc.com), or reconstruct it
  from the dump + the sources we already have.

## Command protocol recovered so far

From the game driver (`TeslaRel410\CODE\RP\MUNGA_L4\L4PLASMA.CPP`) and the
factory test tool (`…\VWETEST\VGLTEST\PLASMA.EXE`). Full grammar lives in
[`../src/VPlasma.Core/Protocol/PlasmaProtocol.cs`](../src/VPlasma.Core/Protocol/PlasmaProtocol.cs).

| Bytes | Meaning |
|-------|---------|
| `ESC @` | Clear screen, reset text state |
| `ESC L` | Home cursor |
| `ESC G n` | Cursor mode (00/FF hidden, 01 steady, 03 flashing) |
| `ESC K n` | Font select (0–7; FF = default) |
| `ESC H n` | Text attributes (intensity / underline / reverse / flash) |
| `ESC P s y x w h  data…` | Graphics write: MSB = leftmost pixel |
| BS / HT / LF / VT / CR | Cursor motion |

The Babcock manual (or a firmware dump) would fill in exact operand
encodings, tab stops, the `ESC P` "screen" byte, and any commands the game
never used.

## JP1 configuration header

Traced pin-by-pin (see the jumper photo). **JP1 is firmware-read
configuration, not CPU mode select** — each shunt ties a GP port pin the
firmware polls at boot. Shunt to GND = logic 0.

| JP1 pos | HC11 pin | Function |
|---------|----------|----------|
| 1 | pin 24 / PA0 | Baud select bit 0 |
| 2 | pin 22 / PA2 | Baud select bit 1 |
| 3 | pin 21 / PA3 | Option (unknown) |
| 4 | pin 15 / PD5 | Option (unknown) |
| 5 | pin 14 / PD4 | Option (unknown) |
| 6 | pin 13 / PD3 | Option (unknown) |
| 7 | J2 SEL → +5 V | Parallel interface select |

Positions 1–2 = the datasheet's baud "JUMPER 1 / JUMPER 2." Positions 3–6
are four unknown firmware option bits — candidates for a hidden factory
self-test / diagnostic mode.

HC11 pin map cross-checked while tracing: PD0–PD5 = pins 10–15, PA0–PA7 =
pins 24–17 (descending).

**MODA/MODB are hardwired high (expanded mode) through a diode to +5 V — not
jumper-selectable.** So bootstrap mode cannot be entered by moving a jumper;
it needs a mode-pin override. (Exact diode circuit still to be characterized.)

## Firmware-dump plan

Goal: get the 64 KB EPROM image, disassemble the HC11 code to recover the
full command table + font bitmaps + timing, then differential-test vPLASMA
against the real panel on identical byte streams. The recovered spec feeds
**both** vPLASMA and the replacement firmware.

1. **Free, no-solder — hunt for a diagnostic mode.** Capture J1 TxD while
   power-cycling normally (may emit a banner/version), then step the four
   unknown config jumpers (PA3, PD5, PD4, PD3) through combinations watching
   TxD for a factory self-test or ROM dump.
2. **Serial bootstrap (conditional).** Bootstrap needs MODA = MODB = 0 at the
   reset edge; they're pulled to +5 V via a diode. If that circuit has a
   series resistor (or a diode-OR node), pull both low during a reset pulse
   and run the standard **Motorola AN1060** dump loader out J1 — no cutting.
   If hard-tied, a single trace cut/lift is needed. *Blocked on the diode
   details.*
3. **Reliable fallback — read the EPROM directly.** PLCC-32 test clip on U3
   with the HC11 held in reset, or hot-air U3 off and read it in a 27C512
   adapter. Guaranteed image.

Safety: the panel runs on a few hundred volts from the on-board DC-DC. Keep
all work in the logic corner (HC11 / EPROM / MAX202); never probe the HV
section or the panel connector while powered.

## Open items

- Characterize the MODA/MODB diode circuit → decide if serial bootstrap is a
  tack-a-wire job or needs a trace cut.
- Capture J1 TxD across config-jumper combinations (path 1).
- Obtain the Babcock PD01D programming manual, **or** dump the U3 EPROM.
- Once we have the command table + fonts: fold into `VPlasmaDevice`, replace
  the public-domain 5×7 stand-in with the real Babcock glyphs, and
  differential-test against the hardware.
- **Prototype the replica.** A modern MCU (RP2040 / ESP32 / Teensy) reads the
  command stream into the same command parser and drives a 128×32 LED matrix
  from the same frame buffer — the per-pixel lit / half-intensity / flash
  flags in `VPlasmaDevice` map directly onto PWM brightness + blink. An amber
  matrix best mimics the neon-orange plasma; for a true cockpit swap, match
  the original active area (~12.75" × 3.15", ~0.1" pitch = 128×32).

## Replica interface — USB, not RS-232

The cockpit PCs are now **Win x64**, so the replica likely needs **no real
serial port**: a native-USB MCU presenting as a **USB CDC virtual COM port**
is transparent — the host opens `COMx` and can't tell it isn't a UART. This
deletes the RS-232 transceiver and connector from the BOM. Consequences:

- **Baud is cosmetic** over USB CDC (the 9600/… setting is accepted as a
  no-op; the two baud-select jumpers need no hardware equivalent).
- **Timing becomes instant** rather than ~1 ms/byte — harmless for a display,
  and vPLASMA can still throttle to mimic the original for differential tests.
- **Pin the COM number** the host expects (original was COM2) in Device
  Manager so it drops in with no host-side config change.
- **DTR/RTS still cross** the CDC link if any host logic ever needs them (the
  game didn't use flow control).
- **Power gotcha:** USB alone can't drive the LED array at full brightness —
  use USB for data + a **separate DC feed** for the LEDs (or USB-C PD).

Transparency assumes the host reaches the display as a Windows `COMx`
endpoint — e.g. DOSBox-X `serial2=directserial realport:COMx`, which a USB
CDC port satisfies perfectly. Confirm the current drive path.

## Status

**Parked pending a firmware dump.** The software emulator (vPLASMA) is built
and released; this hardware/protocol thread is blocked on getting the U3
EPROM image (or the Babcock programming manual). Resume at the dump plan
above once a dump is in hand.
