L0 ROM

Toshiba LO ROM chip taken from an AES system.

File:Cd2 lo.jpg

LO ROM chip found on a CDM3-2 board.

The L0 ROM is a 64KiB sprite scaling lookup table found in every NeoGeo system as a standalone mask ROM or integrated in NEO-GRZ.

The 000-lo.lo dump commonly found in system ROM sets is 128KiB but only the first half is used.

Hash

• CRC32: 5A86CFF2
• SHA-1: 5992277DEBADEB64D1C1C64B0A92D9293EAF7E4A

Data format

The data is made of 256 tables of 256 bytes, each table corresponding to a vertical shrinking value for sprites.

For the first 256 lines (top half of a full sprite), the index in the table is the pixel row number of the sprite currently being drawn (scanline - Y position).

Each byte entry in the table is used as 2 nibbles:

• The upper nibble is the index to read in the tilemap in VRAM SCB1 (0 to 15).
• The lower nibble is the pixel row number of that tile to fetch in the C ROMs.

For the last 256 lines (bottom half of a full sprite), the index in the table is complemented: the table is read backwards.

• The upper nibble is the index XOR 31 to read in the tilemap in VRAM SCB1 (16 to 31).
• The lower nibble is the pixel row number XOR 15 of that tile to fetch in the C ROMs.

Example of GPU processing

(Maybe place this part in the LSPC page ?)

Sprite with Y scaling value = $1B (10.6% of full size).

Sprite line #	L0 address	L0 data	Tilemap index	Pixel row in tile
0	$1B00	$00	0	0
1	$1B01	$08	0	8
2	$1B02	$10	1	0
...
26	$1B1A	$E8	14	8
27	$1B1B	$F8	15	8
28	$1B1C	$FF	15	15
29	$1B1D	$FF	15	15
...

Datasheet

There are 2 stand alone chip versions used depending on the NeoGeo system, the SOP32 TC531001 and the DIP28 TC531000.

Official TC531001 datasheet: [[1]]

Official TC531000 datasheet: [[2]]