| Format | Option name |
|---|---|
| Binary | -fbin |
| Nintendo Game Boy ROM | -fngb |
The Game Boy format is a binary format. Game Boy images must start with a particular header. The linker does not produce this header automatically, but it does calculate the correct checksum.
The first object's first section must contain this header. Alternatively it's possible to specify a load address for a section and place it at the right address.
The normal mode supports banks. The linker will distribute CODE and DATA sections, filling up the lower banks first. Sections may also specify a particular bank if necessary.
These machine definitions declare either an unbanked 32 KiB ROM image or a banked ROM image which can be much larger.
They share some common pools and groups:
| Pool/group | Start | End |
|---|---|---|
| VRAM | $8000 | $9FFF |
| BSS | $C000 | $DFFF |
| HRAM | $FF80 | $FFFF |
This machine definition is used for small mode 32 KiB images. It uses the common pools, and pool defined for the ROM area $0000 to $7FFF. The groups HOME, CODE and DATA all refer to this pool.
This machine definition is used for images larger than 32 KiB. It is banked with each bank being 16 KiB in size. It uses the common pools, one pool for the HOME group, and several pools for CODE/DATA groups.
The HOME group is the area from $0000 to $3FFF, and the CODE/DATA group is several banks mapped into the $4000 to $7FFF. The linker will place CODE/DATA sections in these pools, starting from the pool at the beginning of the ROM image. The bank number can be discovered with the BANK assembler function, and can be used to map the BANK into memory from code.
THe header must be more or less filled correctly by the user, but the linker will correct the following entries:
| Entry | Location |
|---|---|
| "Magic bytes" | $000 |
| Cartridge type | $147 |
| Cartridge size | $148 |
| Checksum | $14D, $14E |