Add a simple boot rom stub

so we can start the emulated console without need for special case in the code, and not adding any copyrighted material in the project.
Also automatically copy the stub rom in the build folder.

CMakeLists.txt

@@ -36,6 +36,13 @@ set_property(TARGET wonderswan PROPERTY CXX_STANDARD 98)
 target_compile_definitions(wonderswan PUBLIC VERSION="${VERSION}")
 target_include_directories(wonderswan PUBLIC source)
 
+add_custom_command(
+        TARGET wonderswan POST_BUILD
+        COMMAND ${CMAKE_COMMAND} -E copy
+        ${CMAKE_SOURCE_DIR}/irom_stub/*.bin
+        ${CMAKE_CURRENT_BINARY_DIR}/
+)
+
 add_subdirectory(source)
 
 target_link_libraries(wonderswan wswan glfw ${OPENGL_glu_LIBRARY} ${OPENGL_gl_LIBRARY})

irom_stub/Makefile

@@ -0,0 +1,20 @@
+.PHONY: all clean
+
+all: ws_irom.bin wsc_irom.bin wc_irom.bin
+	
+clean:
+	@echo " RM"
+	@rm -f *.bin	
+
+ws_irom.bin: irom_stub.asm
+	@echo " AS $@"
+	@nasm $^ -o $@ -DWONDERSWAN=1
+
+wsc_irom.bin: irom_stub.asm
+	@echo " AS $@"
+	@nasm $^ -o $@ -DWONDERSWANCOLOR=1
+	
+wc_irom.bin: irom_stub.asm
+	@echo " AS $@"
+	@nasm $^ -o $@ -DSWANCRYSTAL=1
+	

irom_stub/irom_stub.asm

@@ -0,0 +1,104 @@
+; WonderSwan Internal ROM Stub
+; --------------------------------------
+; Version 1.0
+
+; This is a replacement for the internal rom to prevent using/including any copyrighted material.
+; It does nothing, just lauching the cartridge.
+; It may later include a bootsplah.
+
+%ifdef WONDERSWAN
+%define ROM_SIZE 4096
+%define ROM_SEG 0FF00h
+%else
+%define ROM_SIZE 8192
+%define ROM_SEG 0FE00h
+%endif
+
+; Setup NASM for a 80186
+	bits 16
+	cpu  186
+
+	org 0000h
+    
+%define JUMPER_LOCATION 0000h:0400h
+; ---------------------------------------------------------------------------------------------
+; Boot ROM jumper
+; ---------------------------------------------------------------------------------------------
+; Lock the bootrom
+; Clear a bit of itself
+; Jump to FFFF:FFF0
+; 
+; Must be copied to 0000:0400 then jmp 0000:0400
+ram_jumper:
+    
+    ; Lock the boot rom away
+    IN al, 0A0h
+    OR al, 001h ; Bit 0 lock the boot rom
+    out 0A0h, al
+    
+    mov ax, cs
+    mov es, ax
+    mov di, 0400h
+    mov cx, (.rm_te_end - ram_jumper)
+    xor ax, ax
+    xor bx, bx
+.rm_te_end:
+    rep stosb
+    jmp 0FFFFh:00000h
+ram_jumper_end:
+
+_start:
+    cli
+    cld
+    push cs
+    pop ds
+    xor ax, ax
+    mov es, ax
+
+    ; Clear the IRAM
+    mov     di, 0
+    mov     cx, 16384
+    xor     al, al
+    rep stosb           ; STOSB -> ES:DI
+
+    ; Copy the jumper
+    mov     si, ram_jumper
+    mov     cx, (ram_jumper_end - ram_jumper)
+    mov     di, 0400h
+    xor     ax, ax
+    mov     es, ax
+    rep movsb         ; DS:SI -> ES:DI
+
+    ; Do some register cleanup
+    mov     al, 0FFh
+    out     0C0h, al
+    out     0C1h, al
+    out     0C2h, al
+    xor     ax, ax
+    xor     cx, cx
+    xor     dx, dx
+    mov     ds, ax
+    mov     es, ax
+
+    ; Jump to the jumper!
+    jmp JUMPER_LOCATION
+    
+%ifdef WONDERSWAN
+    db "WonderSwan"
+%elifdef WONDERSWANCOLOR
+    db "WonderSwan Color"
+%elifdef SWANCRYSTAL
+    db "WonderSwan Crystal"
+%else
+%endif
+    db " internal ROM Stub for NewOswan (c)2021 986-Studio"
+; Create at the end of the block, add padding if needed
+TIMES (ROM_SIZE - 16) - ($-$$) DB 0FFh
+
+    jmp ROM_SEG:_start              ; 0
+    db 00        ; ??               ; 5
+    db 0F0h      ; Dev ID           ; 6
+    db 00        ; Min Swan type    ; 7
+    db 00000100b ; flags            ; C
+    db 01        ; No RTC           ; D
+    dw 0FFFFh    ; CRC (need to update it after, but as not used by the rom, no need for now)