Emulator Overview

The BE-300 emulator is a GXemul 0.7.0-based system emulator for the Casio Cassiopeia BE-300. It runs the same VR4131 MIPS CPU model, ROM reset vector, NAND boot path, and companion-chip peripherals that the stock device depends on.

The active target is accurate Windows CE 3.0 cold boot from the real 16 KB masked boot ROM and a raw NAND restore image:

./be300 --nand ce/restore_images/All_nand_300.bin

That path runs:

ROM reset vector -> SPL/Kloader from NAND -> NK.exe decompression -> WinCE 3.0

Current Status

• WinCE 3.0 cold boot reaches the shell / first-boot UI path from the unmodified ROM and NAND image.
• Touch input is usable enough to complete calibration and reach applications.
• Native boots default to the cold-boot RTC presentation so WinCE can ask for date/time like real hardware after battery removal.
• --rtc-host-time initializes the guest RTC from host local time for interactive testing.
• CompactFlash, PCMCIA NE2000, Stowaway keyboard, PC Connect bridge, and the PPSH debug-shell probe are implemented as targeted accessory paths.
• Linux kernel boot support remains in the codebase for historical and regression work, but current CLI and regression focus are WinCE NAND boots.

Development rule

Guest binaries stay unmodified. The emulator should model missing hardware behavior instead of patching WinCE, pre-seeding RAM, or forcing handoff state.

Key Features

Feature	Details
CPU	NEC VR4131-class MIPS, GXemul CP0/TLB/MMU, MIPS32 and MIPS16
Boot ROM	16 KB masked ROM embedded from docs/hardware/be300_boot_rom.bin
RAM	16 MiB default SDRAM, configurable with --sdram
Display	240x320 guest framebuffer, optional SDL2 host window and BE-300 frame
NAND	Samsung K9F2808U0B-style NAND controller model with OOB/ECC synthesis
Input	VRC4173 PIU touchscreen, front buttons, optional Stowaway serial keyboard
Storage	ATA CompactFlash image support and NANDWRITER restore path
Networking	PCMCIA NE2000 model with native and WebAssembly bridge hooks
Serial	VRC4173 SIU UART, PPSH probe, PC Connect time-sync peer, PC Connect bridge
Frontends	Native CLI/SDL, WebAssembly worker/frontend, Android JNI app
Diagnostics	MMIO logging, first-hit MMIO coverage, trace mode, stall detection

Screenshots

WinCE 3.0 NAND Boot

Linux PicoGUI Desktop