[Nov/17/99]

ST-V BIOS (Sega Titan Video)

Hardware : 171-6847D (Sega 1984)
Number : 834-11579

Eprom 17951 is the japanese version of the bios.
Eprom 17952 is the united sates version.

There is just 4 differents bytes between the two versions.

Offset       JP      US

00809        4A      55
03069        10      40
7FFFE        18      1D
7FFFF        99      FD

ST-V hardware description :

	CPU	2 x HITACHI SH-2 (HD6417095)
	SNDCPU	1 x MC68EC000FN12 (68000)
	SOUND	1 x 315-5687 (YMF292-F)
		  + 315-5689 (HD64440F) ???
	OTHER	1 x 315-5690 (FH3006)
		1 x 315-5688 (FH3007)
		1 x 315-5778
		1 x 315-5744

The board is Jamma, the test and service switches are located on the board itself.

November 17th, 1999.

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[MAME]

Sega ST-V (Sega Titan Video)

a.k.a. known as a Sega Saturn for the Arcades.

Driver by David Haywood,Angelo Salese,Olivier Galibert & Mariusz Wojcieszek
SCSP driver provided by R.Belmont,based on ElSemi's SCSP sound chip emulator
CD Block driver provided by ANY,based on sthief original emulator
Many thanks to Guru,Fabien & Runik for the help given.

Hardware overview:
------------------
-two SH-2 CPUs,in a master/slave configuration.The master cpu is used to
boot-up and to do the most of the work,the slave one does extra work that could be
too much for a single cpu.They both shares all the existant devices;
-a M68000 CPU,used to drive sound(the SCSP chip).The program is uploaded via the
SH-2 cpus;
-a SMPC (System Manager & Peripheral Control),used to drive all the
devices on the board;
-a SCU (System Control Unit),mainly used to do DMA operations and to drive interrupts,it
also has a DSP;
-an (optional for the ST-V) SH-1 CPU,used to be the CD driver;
-An A-Bus,where the cart ROM area is located;
-A B-Bus,where the Video Hardware & the SCU sections are located;
-Two VDPs chips(named as 1 & 2),used for the video section:
 -VDP1 is used to render sprites & polygons.
 -VDP2 is for the tilemap system,there are:
 4 effective normal layers;
 2 roz layers;
 1 back layer;
 1 line layer;
 The VDP2 is capable of the following things (in order):
 -dynamic resolution (up to 704x512) & various interlacing modes;
 -mosaic process;
 -scrolling,scaling,horizontal & vertical cell scrolling & linescroll for the
  normal planes, the roz ones can also rotate;
 -versatile window system,used for various effects;
 -alpha-blending,refered as Color Calculation in the docs;
 -shadow effects;
 -global rgb brightness control,separate for every plane;

this hardware comes above hell on the great list of hellish things as far as emulation goes anyway ;-)

Memory map:
-----------

0x00000000, 0x0007ffff  BIOS ROM
0x00080000, 0x000fffff  Unused
0x00100000, 0x00100080  SMPC
0x00100080, 0x0017ffff  Unused
0x00180000, 0x0018ffff  Back Up Ram
0x00190000, 0x001fffff  Unused
0x00200000, 0x002fffff  Work Ram-L
0x00300000, 0x00ffffff  Unused
0x01000000, 0x01000003  MINIT
0x01000004, 0x017fffff  Unused
0x01800000, 0x01800003  SINIT
0x01800004, 0x01ffffff  Unused
0x02000000, 0x03ffffff  A-BUS CS0
0x04000000, 0x04ffffff  A-BUS CS1
0x05000000, 0x057fffff  A-BUS DUMMY
0x05800000, 0x058fffff  A-BUS CS2
0x05900000, 0x059fffff  Unused
0x05a00000, 0x05b00ee3  Sound Region
0x05b00ee4, 0x05bfffff  Unused
0x05c00000, 0x05cbffff  VDP 1
0x05cc0000, 0x05cfffff  Unused
0x05d00000, 0x05d00017  VDP 1 regs
0x05d00018, 0x05dfffff  Unused
0x05e00000, 0x05e7ffff  VDP2
0x05e80000, 0x05efffff  VDP2 Extra RAM,accessible thru the VRAMSZ register
0x05f00000, 0x05f00fff  VDP2 Color RAM
0x05f01000, 0x05f7ffff  Unused
0x05f80000  0x05f8011f  VDP2 regs
0x05f80120, 0x05fdffff  Unused
0x05fe0000, 0x05fe00cf  SCU regs
0x05fe00d0, 0x05ffffff  Unused
0x06000000, 0x060fffff  Work Ram-H
0x06100000, 0x07ffffff  Unused

*the unused locations aren't known if they are really unused or not,needs verification,most
of them seem just mirrors of the previous valid memory allocated.

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