Target

The choice of the target determines the final format of the game: ROM, disk, etc.

It is a parameter used by the Build Tool to adapt your code to the target during the construction of the final program and to assemble the data to be compatible with the target.

The choice of the format is made in the project configuration file (project_config.js).

Here is a description of the different target formats available in MSXgl.

Basic program

Binary program to be executed from the BASIC environment using bload function.

Target	Description
BIN	BASIC binary program (starting at 8000h)
BIN_USR	BASIC USR binary driver (starting at C000h)
BAS	Alias for BIN

Note: The maximum size of a BASIC program is about 24 KB (including variables).

The Build tool deployment step places your final program in two formats:

• .bin format in emul/bin/ folder
• .dsk format in emul/dsk/ folder (image of a disk containing your program)

MSX-DOS program

Binary program to be executed from the MSX-DOS environment.

Target	Description
DOS1	MSX-DOS 1 program (starting at 0100h)
DOS2	MSX-DOS 2 program (starting at 0100h)
DOS	Alias for DOS1
DOS0	Direct program boot from disk (starting at 0100h)
BOOT	Alias for DOS0

Note:

• The maximum size of a MSX-DOS program is about 53 KB (including variables).
• For "DOS0" target, maximum is 48 KB (excluding variables).

The Build tool deployment step places your final program in two formats:

• .com format in emul/dosX/ folder (dos1, dos2 ou dos0)
• .dsk format in emul/dsk/ folder (image of a disk containing your program)

Plain ROM program

Binary program to be written into a ROM from 8 to 64 KB and executed from a cartridge.

Target	Description
ROM_8K	8 KB ROM in page 1 (4000h ~ 5FFFh)
ROM_8K_P2	8 KB ROM in page 2 (8000h ~ 9FFFh)
ROM_16K	16 KB ROM in page 1 (4000h ~ 7FFFh)
ROM_16K_P2	16 KB ROM in page 2 (8000h ~ BFFFh)
ROM_32K	32 KB ROM in page 1&2 (4000h ~ BFFFh)
ROM_48K	48 KB ROM in page 0-2 (0000h ~ BFFFh)
ROM_48K_ISR	48 KB ROM in page 0-2 (0000h ~ BFFFh) with ISR replacement
ROM_64K	64 KB ROM in page 0-3 (0000h ~ FFFFh)
ROM_64K_ISR	64 KB ROM in page 0-3 (0000h ~ FFFFh) with ISR replacement
ROM	Alias for ROM_32K

See also: Create a plain ROM.

The Build tool deployment step places your final program in emul/rom/ folder.

Mapped ROM program

Note: "MegaROM" refers to a ROM of 128 KB or more. Even though they are not widely supported, there is nothing to prevent you from creating a 64 KB ROM using a mapper. We therefore prefer to use the term Mapped ROM here rather than MegaROM.

Setup

You can create program using one of the ROM mappers supported by MSXgl:

Target	Description
ROM_ASCII8	ASCII-8: 8 KB segments for a total of 64 KB to 2 MB
ROM_ASCII16	ASCII-16: 16 KB segments for a total of 64 KB to 4 MB
ROM_KONAMI	Konami MegaROM (aka Konami4): 8 KB segments for a total of 64 KB to 2 MB
ROM_KONAMI_SCC	Konami MegaROM SCC (aka Konami5): 8 KB segments for a total of 64 KB to 2 MB

In your build.bat, chose as target one of the above target type. You can specify the ROM size (in KB) in the ROMSize variable. Default value is 128 (KB). Any multiple value of the mapper's segment size is valid, but I recommend using powers of 2 values (64, 128, 256, etc.) to help emulators to autodetect the right mapper.

Some Build Tool configuration examples:

//-- 128 KB ASCII-8 mapped-ROM
target = "ROM_ASCII8";

//-- 4 MB ASCII-16 mapped-ROM
target = "ROM_ASCII16";
ROMSize = 4096;

//-- 512 KB Konami SCC mapped-ROM
target = "ROM_KONAMI_SCC";
ROMSize = 512;

See projects/samples/s_vgm sample for a concrete use case.

The Build tool deployment step places your final program in emul/rom/ folder.

Build

Mapped-ROM use a system of sub-page (called "bank" here) the user can redirect to any segment of the ROM. Those banks are mapped to page #1 and #2 (4000h~BFFFh) of the memory space. The number of banks depends on the size of the mapper:

• 8 KB mappers have 4 banks:
  • bank 0: 4000h~5FFFh
  • bank 1: 6000h~7FFFh
  • bank 2: 8000h~9FFFh
  • bank 3: A000h~BFFFh
• 16 KB mappers have 2 banks:
  • bank 0: 4000h~7FFFh
  • bank 1: 8000h~BFFFh

The Build Tool build the first 32 KB of the mapped-ROM like a 32 KB plain ROM. This represents the first 4 segments for a 8 KB mapper and the first 2 for a 16 KB mapper.

The following segments are added to the ROM by the Build Tool by searching for files with a particular nomenclature: <project_name>_s<segment_number>_b<target_bank>.c.

For example with a ASCII-8 ROM of 128 KB:

program.c          | Main program including segment #0~#3 (4*8 KB)
program_s4_b2.c    | Segment #4 to be used in bank #2 (8000h~9FFFh)
program_s5_b3.c    | Segment #5 to be used in bank #3 (A000h~BFFFh)
                   | No files found for segment #6 to #14: padding data added to the ROM
program_s15_b2.c   | Segment #15, the last one, to be used in bank #2 (8000h~9FFFh)

Segment selection

In your program, you can then select what segment is visible from what bank using the SET_BANK_SEGMENT(bank, seg) macro. For example, to put segment 15 of the above example in bank 2, just use SET_BANK_SEGMENT(2, 15);

For information, at startup, the following segments are selected:

• 8 KB mappers:
  • bank 0: segment 0
  • bank 1: segment 1
  • bank 2: segment 2
  • bank 3: segment 3
• 16 KB mappers:
  • bank 0: segment 0
  • bank 1: segment 1

For more detail, see Create a mapped ROM article.

Targets overview

Target	Selected at boot				Description
	P0	P1	P2	P3
ROM_8K	BIOS	Cart	RAM	RAM	8 KB ROM in page 1 (4000h ~ 5FFFh)
ROM_8K_P2	BIOS	RAM	Cart	RAM	8 KB ROM in page 2 (8000h ~ 9FFFh)
ROM_16K	BIOS	Cart	RAM	RAM	16 KB ROM in page 1 (4000h ~ 7FFFh)
ROM_16K_P2	BIOS	RAM	Cart	RAM	16 KB ROM in page 2 (8000h ~ BFFFh)
ROM_32K	BIOS	Cart	Cart	RAM	32 KB ROM in page 1&2 (4000h ~ BFFFh)
ROM_48K	BIOS	Cart	Cart	RAM	48 KB ROM in page 0-2 (0000h ~ BFFFh)
ROM_48K_ISR	Cart	Cart	Cart	RAM	48 KB ROM in page 0-2 (0000h ~ BFFFh) with ISR replacement
ROM_64K	BIOS	Cart	Cart	RAM	64 KB ROM in page 0-3 (0000h ~ FFFFh)
ROM_64K_ISR	Cart	Cart	Cart	RAM	64 KB ROM in page 0-3 (0000h ~ FFFFh) with ISR replacement
ROM_ASCII8	BIOS	Cart	Cart	RAM	ASCII-8: 8KB segments for a total of 64 KB to 2 MB
ROM_ASCII16	BIOS	Cart	Cart	RAM	ASCII-16: 16KB segments for a total of 64 KB to 4 MB
ROM_KONAMI	BIOS	Cart	Cart	RAM	Konami MegaROM (aka Konami4): 8 KB segments for a total of 64 KB to 2 MB
ROM_KONAMI_SCC	BIOS	Cart	Cart	RAM	Konami MegaROM SCC (aka Konami5): 8 KB segments for a total of 64 KB to 2 MB
DOS1	RAM	RAM	RAM	RAM	MSX-DOS 1 program (starting at 0100h)
DOS2	RAM	RAM	RAM	RAM	MSX-DOS 2 program (starting at 0100h)
DOS0	RAM	RAM	RAM	RAM	Direct program boot from disk (starting at 0100h)
BIN	BIOS	BASIC	RAM	RAM	BASIC binary program (starting at 8000h)
BIN_USR	BIOS	BASIC	RAM	RAM	BASIC USR binary driver (starting at C000h)

Main

For ROM or Basic program, the main function prototype is:

void main();

For DOS1 target, this prototype can also be used to get command-line arguments (set DOSParseArg to allow arguments parsing):

void main(u8 argc, const c8** argv);

For DOS2 target, this prototype can also be used to return a value du MSX-DOS:

u8 main();
u8 main(u8 argc, const c8** argv);

• argc: Integer that contains the number of arguments present in argv. The argc parameter can be 0 if no parameter have been added to the command line.
• argv: Array of null-terminated strings representing command-line arguments entered by the user of the program.
• return: The return value can be catch by MSX-DOS 2 as an error code to know if program process succeeded or not.