L0 ROM: Difference between revisions

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[[File:aes_lo.jpg|right|thumb|Toshiba LO ROM chip taken from an AES system.]]
[[File:aes_lo.jpg|right|thumb|Toshiba LO ROM chip taken from an AES system.]]
[[File:cd2_lo.jpg|right|thumb|LO ROM chip found on a CDM3-2 board.]]
[[File:cd2_lo.jpg|right|thumb|LO ROM chip found on a CDM3-2 board.]]
[[File:Ngscaling.png|right|thumb]]


LO stands for "LOokup". It's a 64KiB (sometimes 128KiB with A16 tied to ground) ROM chip found in every NeoGeo systems, which contains byte values used by the [[GPU]] to shrink [[sprites]] vertically.
The L0 ROM is a 64KiB (sometimes 128KiB with A16 tied to ground) ROM chip found in every NeoGeo systems as a stand alone chip or integrated in another [[NEO-GRZ|chip]], which contains byte values used by {{Chipname|LSPC}} to shrink [[sprites]] '''vertically'''.
 
The dump is called 000-lo.lo in [[system ROM]] sets.
 
=Hash=


The dump is often called 000-lo.lo in [[BIOSes|BIOS]] sets.
* CRC32: 5A86CFF2
* SHA-1: 5992277DEBADEB64D1C1C64B0A92D9293EAF7E4A


==Data==
=Data format=


The data contained in this ROM is actually 256 tables of 256 bytes, each table corresponding to a value of the vertical shrinking for sprites.
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 (first half of a full sprite), the index in the table is the horizontal line number of the sprite currently being drawn (scanline - Y position).
For the first 256 lines (top half of a full sprite), the index in the table is the line number of the sprite currently being drawn (scanline - Y position).


Each byte is used as 2 nibbles:
Each byte entry in the table is used as 2 nibbles:
*The upper nibble is the tile number index to read in the tilemap table in VRAM SCB1 (0 to 15).
*The upper nibble is the tile number index to read in the tilemap in [[VRAM]] SCB1 (0 to 15).
*The lower nibble is the line number of that tile to fetch in the [[C ROM]]s.
*The lower nibble is the line number of that tile to fetch in the [[C ROM]]s.


For the last 256 lines (second half of a full sprite), the index in the table is 255-((scanline - Y position) & 255). The table is read backwards.
For the last 256 lines (bottom half of a full sprite), the index in the table is complemented: the table is read backwards.


Each byte is used as 2 nibbles:
*The upper nibble is the tile number index XOR $1F to read in the tilemap in VRAM SCB1 (16 to 31).
*The upper nibble is the tile number index XOR $1F to read in the tilemap table in VRAM SCB1 (0 to 15).
*The lower nibble is the line number XOR $F of that tile to fetch in the C ROMs.
*The lower nibble is the line number XOR $F of that tile to fetch in the C ROMs.


==Example of GPU processing==
==Example of GPU processing==
[[File:Ngscaling.png|right|thumb]]


(Maybe place this part in the GPU page ?)
(Maybe place this part in the LSPC page ?)


Sprite with Y zoom value = $1B and tile height = 2 (32 pixels).
Sprite with Y zoom value = $1B and tile height = 2 (32 pixels).


*Line 0 of sprite. GPU asks LO data at address $1B00. Data is $00: Tilemap index 0, line 0 of tile.
{|class=wikitable
*Line 1 of sprite. GPU asks LO data at address $1B01. Data is $08: Tilemap index 0, line 8 of tile.
!Sprite line #
*Line 2 of sprite. GPU asks LO data at address $1B02. Data is $10: Tilemap index 1, line 0 of tile.
!L0 address
...
!L0 data
*Line 26 of sprite. GPU asks LO data at address $1B1A. Data is $E8: Tilemap index is $E, line 8 of tile.
!Tilemap index
*Line 27 of sprite. GPU asks LO data at address $1B1B. Data is $F8: Tilemap index is $F, line 8 of tile.
!Tile line used
*Line 28 of sprite. GPU asks LO data at address $1B1C. Data is $FF: Tilemap index is $F, line $F of tile.
|-
*Line 29 of sprite. GPU asks LO data at address $1B1D. Data is $FF: Tilemap index is $F, line $F of tile.
|0||$1B00||$00||0||0
...
|-
|1||$1B01||$08||0||8
|-
|2||$1B02||$10||1||0
|-
|colspan=5|...
|-
|26||$1B1A||$E8||14||8
|-
|27||$1B1B||$F8||15||8
|-
|28||$1B1C||$FF||15||15
|-
|29||$1B1D||$FF||15||15
|-
|colspan=5|...
|}


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


Official TC531001 datasheet: [[http://www.alldatasheet.com/datasheet-pdf/pdf/115078/TOSHIBA/TC531001.html]]
Official TC531001 datasheet: [[http://www.alldatasheet.com/datasheet-pdf/pdf/115078/TOSHIBA/TC531001.html]]
Official TC531000 datasheet: [[https://www.digchip.com/datasheets/parts/datasheet/710/TC531000CP-pdf.php]]


[[Category:Chips]]
[[Category:Chips]]

Latest revision as of 21:37, 21 May 2020

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 (sometimes 128KiB with A16 tied to ground) ROM chip found in every NeoGeo systems as a stand alone chip or integrated in another chip, which contains byte values used by LSPC to shrink sprites vertically.

The dump is called 000-lo.lo in system ROM sets.

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 line 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 tile number index to read in the tilemap in VRAM SCB1 (0 to 15).
  • The lower nibble is the line 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 tile number index XOR $1F to read in the tilemap in VRAM SCB1 (16 to 31).
  • The lower nibble is the line number XOR $F of that tile to fetch in the C ROMs.

Example of GPU processing

(Maybe place this part in the LSPC page ?)

Sprite with Y zoom value = $1B and tile height = 2 (32 pixels).

Sprite line # L0 address L0 data Tilemap index Tile line used
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]]

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