NgDataLinker 1.0

Coded by OzzyOuzo on Feb 11 2021.

wtf

Unleash your Neo.Geo AES/MVS homebrew with 8x time more P memory :)

switch mecanism

Bank switching enables access to a maximum of 9MB PROM memory.

Linear view such as [0x00100000-0x009fffff] is common place,

But bank switching mecanism allows only 1MB from 8MB of P2 Rom to be accessible by configuration switch.

The content of P1 Rom generally always sits between range [0x00100000-0x001fffff]. while 1MB pages from P2 Rom will be alternatively mapped to [0x00200000-0x002fffff].

Selecting the P Roms configuration is done by writing a 16b word at address : 0x2ffff0

code:

void reSetSpriteBank(u16 bank_)
{
	(*((u16*)0x2ffff0)) = bank_;
}

configurations for a 8MB P2 Rom size (only 3bits are used to describe bank config) :

first 1MB of P2 Rom is mapped at 0x200000 which is default configuration

bank_ = 0 : (P1)-(P2-0) from memory range (0x100000)-(0x200000-0x2fffff) (default)

second 1MB page from P2 Rom starting at linear address 0x300000 is mapped at address 0x200000

bank_ = 1 : (P1)-(P2-1) from memory range (0x100000)-(0x300000-0x3fffff) 

third 1MB page from P2 Rom starting at linear address 0x400000 is mapped at address 0x200000

bank_ = 2 : (P1)-(P2-2) from memory range (0x100000)-(0x400000-0x4fffff) 

(etc etc etc)

bank_ = 3 : (P1)-(P2-3) from memory range (0x100000)-(0x500000-0x5fffff) 
....
bank_ = 7 : (P1)-(P2-7) from memory range (0x100000)-(0x900000-0x9fffff) 

example

A common usage for bank switching is to get access to sprite map data located in different banks before updating vram.

1. select appropriate bank configuration to bind proper data.
2. update vram
3. a good idea would be to get back to default conf but you are the boss afterall ^^

pseudo code:

reSetSpriteBank(7);
writeSpriteVram(...);
reSetSpriteBank(0);

NGDataLinker

NGDataLinker will generate consistent addresses needed during link phase for data accessed through bank switching mecanism on P roms. Memory offsets are retreived from map files generated from GCC 2.95.2 which is part of NEODEV SDK.

pre-requisites

Get Romwak 0.3f or above to further use concatenate option /c -> ( https://github.com/freem/romwak )

You need to compile and link each 1MB P Rom separately and link sequence should look as follow :

@REM Pseudo Makefile

@REM Compile example program which contains some of your data (let say some tables)
gcc -I%NEODEV%\m68k\include -m68000 -O3 -Wall -fomit-frame-pointer -ffast-math -fno-builtin -nostartfiles -nodefaultlibs -D__cart__ -c %SRCDIR%\dummyData.c -o %NEODEV%\tmp\dummyData.o

@REM Compile example from binary to object (let say a sprite map from gfxcc.exe for instance)
bin2elf dummy.map dummyMapSprite %NEODEV%\tmp\dummyMapSprite.o


@REM link program
@REM is generating foo2.map cooresponding to P2 ROM (p2rom.o)
gcc -L%NEODEV%\m68k\lib -m68000 -O3 -Wall -fomit-frame-pointer -ffast-math -fno-builtin -nostartfiles -nodefaultlibs -D__cart__ -Wl,-Map,foo2.map %NEODEV%/tmp/yourData.o %NEODEV%\tmp\dummyMapSprite.o -o p2rom.o

@REM Pad program rom
objcopy --gap-fill=0x00 --pad-to=0x100000 -R .data -O binary p2rom.o dev_p2.rom

(eventually you are repeating this process using multiple makefiles resulting in outputs : dev_p2.rom , dev_p3.rom, ... , dev_p9.rom )

usage

ngDataLinker <GCC map file> <out directory>

the command:

ngDataLinker foo2.map ./

will generate header foo2.h in the current directory.

continuing with our pseudo makefile example foo2.h content should be as follow:

#ifndef _FOO2_H_
#define _FOO2_H_

//
//Generated by ngDataLinker 1.0 coded by Ozzy 
//



#define dummyData 		0x00200010
#define dummyMapSprite 		0x00255510


#endif //_FOO2_H_

note

All generated headers will always produce data addresses within the range [0x00200010,0x002fffff] which is intended using bank switched memory.

compile and link

Finally, including this header in your code will solve unreferenced data link errors during your main makefile link phase. (build/make)

make P Roms

For compatibility reasons it's better to use two P Rom files.

• 1MB P1 Rom is generated as usual from the main makefile ending with something like the line below :

  objcopy --gap-fill=0x00 --pad-to=0x100000 -R .data -O binary test.o dev_p1.rom

then we need romwak to generate proper Rom format

romwak /f dev_p1.rom 202-p1.bin
romwak /p 202-p1.bin 202-p1.bin 1024 255

• 8MB P2 Rom is concatened with multiple 1MB P roms

simply creating p2 Rom into the proper format

romwak /f dev_p2.rom 202-p2.bin
romwak /p 202-p2.bin 202-p2.bin 1024 255

p3 Rom is converted to the proper rom format and then concatenated with P2 Rom

romwak /f dev_p3.rom 202-p3.rom
romwak /p 202-p3.rom 202-p3.rom 1024 255
romwak /c 202-p2.bin 202-p3.rom 202-p2.bin

(etc etc)

romwak /f dev_p4.rom 202-p4.rom
romwak /p 202-p4.rom 202-p4.rom 1024 255
romwak /c 202-p2.bin 202-p4.rom 202-p2.bin

romwak /f dev_p5.rom 202-p5.rom
romwak /p 202-p5.rom 202-p5.rom 1024 255
romwak /c 202-p2.bin 202-p5.rom 202-p2.bin

romwak /f dev_p6.rom 202-p6.rom
romwak /p 202-p6.rom 202-p6.rom 1024 255
romwak /c 202-p2.bin 202-p6.rom 202-p2.bin

romwak /f dev_p7.rom 202-p7.rom
romwak /p 202-p7.rom 202-p7.rom 1024 255
romwak /c 202-p2.bin 202-p7.rom 202-p2.bin

romwak /f dev_p8.rom 202-p8.rom
romwak /p 202-p8.rom 202-p8.rom 1024 255
romwak /c 202-p2.bin 202-p8.rom 202-p2.bin

romwak /f dev_p9.rom 202-p9.rom
romwak /p 202-p9.rom 202-p9.rom 1024 255
romwak /c 202-p2.bin 202-p9.rom 202-p2.bin

Hurray

Enjoy.