[−][src]Module gba_addresses::oam
Object Attribute Memory (OAM
).
This portion of memory intermixes the Object (OBJ
) Attributes, as well as
the Affine Parameters.
- Object Attributes:
- You get 128 object entries.
- Each complete entry is three 16-bit values. These pseudo-fields are referred to as "attr0", "attr1", and "attr2".
- There's also a 16-bit span that's not part of the object attributes after each set of attributes, before the next attribute entry begins.
- Affine Parameters
- You get 32 affine parameter entries.
- Each complete entry is four 16-bit values. These pseudo-fields are referred to as "pa", "pb", "pc", and "pd".
- The parameters use the memory in between the object attribute memory
entries described above. The the first
pa
is 6 bytes in from the start ofOAM
, thenpb
,pc
, andpd
are strided 8 bytes at a time from there, then the next affine parameter entry begins 8 bytes after that.
You cannot validly write a single byte to OAM
. If you do so, the
8-bits are written to both the upper and lower 8-bits of the given 16-bit
segment of memory. This isn't a big deal, since all the pseudo-fields of the
stuff in OAM
uses 16-bits anyway.
- Size: 1kb
- Wait states: 0
- Bus Size: 32-bit
- Read/Write: 16/32
Constants
OBJ_AFFINE_COUNT | There are 32 affine parameter entries. |
OBJ_AFFINE_PA_BASE_ADDR | Base address of the affine parameter |
OBJ_AFFINE_PB_BASE_ADDR | Base address of the affine parameter |
OBJ_AFFINE_PC_BASE_ADDR | Base address of the affine parameter |
OBJ_AFFINE_PD_BASE_ADDR | Base address of the affine parameter |
OBJ_AFFINE_STRIDE | Stride of each affine parameter entry. |
OBJ_ATTR0_BASE_ADDR | Base address of the object attribute |
OBJ_ATTR1_BASE_ADDR | Base address of the object attribute |
OBJ_ATTR2_BASE_ADDR | Base address of the object attribute |
OBJ_ATTR_COUNT | There are 128 object attribute entries. |
OBJ_ATTR_STRIDE | Stride of each object attribute entry. |
Functions
index_obj_affine_param | Index the affine parameters to a given entry. |
index_obj_attr | Index the object attributes to a given entry. |