Sega Programming FAQ February 5, 1994, Third Edition
=============================================================
This FAQ (Frequently Asked Questions) is about how to program
the Sega Genesis and Mega Drive Video Games Systems.
This file IS Public Domain, and can be used by all, HOWEVER
if you want to use this in a Data Base, or put it up on Gopher,
etc el then you MUST get my permission. You may copy and post
this file elsewhere without my permission.
If you want to add anything, especially game code or
information on the hardware please E-mail me. My E-mail
and real address are below and at the end of this FAQ.
Disclaimer : In no way I am indorsing any products, systems,
etc. What I am doing is providing the information that I
have found throughout internet and other network systems and
reporting them here, with out reverse engineering. All
information is reported as is- I will not accept any
responsibility if you fry your system trying something out.
All copyrights are owned by their respective owners, no
infringements intended.
Henry Rieke
<U6c16@Wvnvm.Wvnet.Edu>
US Mail:
Henry Rieke
Attn: Sega FAQ
161 Poplar Dr
Morgantown, Wv 26505-2340
=============================================================
0.1 Changes, Updates and Coming Soon
1) I've changed the part on the hardware description to be
smaller and easier to understand. If you still want the
whole file on the Sega Hardware internals then I suggest
that you get the file called Hardware.Txt by FTP from
Ftp.spd.louisville.edu under the directory pub\sega
2) This FAQ has a home now (yea!) at Ftp.spd.louisville.edu
(pub\sega) and it can also be found at Busop.cit.wayne.edu
(pub\megadev\incoming) and soon coming to WWW graphic database
in England (more on that later!).
3) I am going to be writing letters soon to all the companies
on the list (See Chapter 3.0, Companies) asking for more
information concerning their products, and details. I will also
be enquiring to Sega about CD programming and Saturn information.
=============================================================
1.0 Questions
Q) What are the differences between Mega Drive and Genesis?
What are the differences between Mega CD and Sega CD?
A) Physically, on the outside, the only difference is the
plastic case, the cartridge shape is slightly different on
the American version, smaller in size. On the inside there
are four jumpers labeled J1 though J4. J1 and J2 is the
language switch, between English and Japanese, J3 and J4
select the output between PAL and NTSC. You can build a
switch that can allow you to select between these options.
The diagram is included in this document (Chapter 5.0,
called "Language Switch"). The reason for the language
switch is to keep people from getting the game before it
is officially released elsewhere in the world. The newer
Sega Machines do not have the jumpers, and hence you can
not build a switch (as of yet).
The difference between Mega CD and Sega CD are internal.
In side the machine there is a ROM BIOS chip which is changed
for different markets. Sega has a version of the BIOS which
will play any system's games, but this is for Game developing.
There is a device called Pro-CDX which will allow you to by-pass
the lockout.
Q) Where to find files on the Sega Genesis/Mega Drive
hardware?
A) You can find the files on the Sega hardware from one of
the following FTP sites. A brief section describing memory
and cartridge ROMs are included in this FAQ. The author
Rick McTeague, is from Louisville and the most current copy
can be found there first.
FTP Ftp.spd.louisville.edu
Pub\sega\hardware.txt
FTP Busop.cit.wayne.edu
Pub\megadev\incoming\hardware.txt
There are also many other files here as well as a few
68000 ASM.
Q) What does it take to program the Genesis?
A) Development kits can be bought from many companies, a list
is included in the section called "Companies". These kits
require an IBM or Amiga computer to compile the code,
which is usually assembly, but can be in C as long as it
can be compiled into binary. SEGA's own kit is extremely
expensive and they are rumored to have slow response time
to answer questions. The price of the kits cost from $1000
to $4000.
Q) Is IBM or Amiga the only two platforms for game
development?
A) As far as I know, yes. The Apple MacIntosh might have
something, but I have not heard anything on this. There is
a system for the Apple IIgs, called Sluggo from Parsons
Engineering. As for the Mac, if you know, please pass it
on. It is rumored that Electronic Arts uses a priority
system on the MacIntosh for porting the games.
Q) How do I program the SEGA CD Rom?
A) I have no idea on programming this device, if you do have
some information please pass it along to me so I can
include it in the next update.
Q) What is Saturn, and how do I program that?
A) Saturn is Sega's next generation game machine, which
is based on Sega's S-1 arcade Machine's motherboard.
Rumor has it that it will allow programming in C as
well as Assembly.
There is good news and bad news as well.
Good news, Microsoft will be writing the OS.
Bad new, Microsoft will be writing the OS.
Q) What else is there on Internet?
A) Well there is the Sega Programming forum, which you can
join by subscribing to it with this command:
Send a message to Listserv@Busop.Cit.Wayne.Edu with the
first line reading SUBSCRIBE MEGADEV
To unsubscribe, do the same above, except the first line
should read UNSUBSCRIBE MEGADEV
There is also Rec.Games.Video.Programmer and
Rec.Games.Video.Sega where you can ask your questions.
There are also files on how to use the old SEGA 3D glasses
with your IBM compatible computer which can be found all
over the place (including the above FTP sites).
=============================================================
2.0 Hardware : This is the inner workings of the Sega system
ROM and Memory. For a better understanding Sega Hardware I
suggest reading Hardware.txt. An up-to-date version of this
file can be gotten by anonymous ftp from Ftp.spd.louisville.edu,
in the file "Pub/sega/Hardware.txt".
Genesis - this information comes from Rick McTeague.
Please send corrections or comments to:
Rick McTeague
Sysrick@starbase.spd.louisville.edu
Disclaimers:
The following information was extracted without the use of
official information from Sega Enterprises, Ltd. I therefore
offer no warranty on the correctness of this information.
Use it at your own risk.
This information was gathered as a personal project, and is
not the responsibility of my employer.
Different versions of the Genesis exist, so I won't suggest
that any of this information is right for anybody's Genesis
but my own.
Sega, Genesis, Sonic the Hedgehog, and Ecco the Dolphin are
trademarks of Sega Enterprises, Ltd. Other trademarks are the
property of their respective companies.
The Cartridge ROM
-----------------
As others on the net have observed, a standard Genesis
cartridge is nothing more than a small printed circuit board
with a ROM on it. There are some cartridges which have
battery-backed RAM for saving high scores, configurations,
etc., but I haven't seen these, so I don't know about them.
If you know of a particular cartridge that has RAM, let me
know so I can go rent one and take it apart (shhhh!) to see
what's in it.
A cartridge contains a word-wide (16 bit) ROM with up to 2
Meg words (4 Mbytes). This is based on the signal !C_CE, which
is used as the cartridge ROM's chip enable on the cartridges
I've looked at, and which is active at addresses $000000-$3fffff.
It may be possible to have more than 4 Mbyte cartridges; if
so, either they ignore the !C_CE line and do their own
address decoding, or there's a register somewhere in the
Genesis which changes the default address decoding scheme for
!_CE.
Note that cartridges are advertised as being "8 Meg"; as far
as I know, is 8 Meg _bits_, not bytes. 1 Mbyte is still
pretty impressive for a game machine.
SONIC uses a 40-pin 256Kx16 (512Kx8) ROM in word mode.
Ecco the Dolphin uses a 42-pin 512Kx16 (1024Kx8) ROM in word
mode. This one confused me because I'd never seen a 42-pin
DIP before, so I thought it was 40 pins. No wonder the
signals didn't look right...
Putting together a little bit of information from a Sharp
data sheet for a 512 Kword ROM with a bit of conjecture based
on the Sonic and Ecco cartridges, this is what I can come up
with for pinouts:
Sonic Ecco
(256 Kword) (512 Kword)
----u----
----u---- A18 1=| |=42 VCC?
A17 1=| |=40 A 8 A17 2=| |=41 A 8
A 7 2=| |=39 A 9 A 7 3=| |=40 A 9
A 6 3=| |=38 A10 A 6 4=| |=39 A10
A 5 4=| |=37 A11 A 5 5=| |=38 A11
A 4 5=| |=36 A12 A 4 6=| |=37 A12
A 3 6=| |=35 A13 A 3 7=| |=36 A13
A 2 7=| |=34 A14 A 2 8=| |=35 A14
A 1 8=| |=33 A15 A 1 9=| |=34 A15
A 0 9=| |=32 A16 A 0 10=| |=33 A16
!CE 10=| |=31 !BYTE !CE 11=| |=32 !BYTE
GND 11=| |=30 GND GND 12=| |=31 GND
!OE 12=| |=29 D15 !OE 13=| |=30 D15
D 0 13=| |=28 D 7 D 0 14=| |=29 D 7
D 8 14=| |=27 D14 D 8 15=| |=28 D14
D 1 15=| |=26 D 6 D 1 16=| |=27 D 6
D 9 16=| |=25 D13 D 9 17=| |=26 D13
D 2 17=| |=24 D 5 D 2 18=| |=25 D 5
D10 18=| |=23 D12 D10 19=| |=24 D12
D 3 19=| |=22 D 4 D 3 20=| |=23 D 4
D11 20=| |=21 VCC D11 21=| |=22 VCC
--------- ---------
Note that the address line numbering is different than that
of the 68000; line A0 of the ROM is really connected to the
68000's A1. This is because of the way the 68000 handles
even/odd byte addressing using !UDS and !LDS.
The !BYTE line is held high. This puts the ROM chip into
"word" mode, where data is accessed 16 bits at a time.
The convenient correspondence between ROM and 68000 data and
address lines (ROM D0 = 68K D0, ROM D1 = 68K D1, etc..., and
ROM A0 = 68K A1, ROM A1 = 68K A2, etc...) may not exist in
all cartridge designs. This is sometimes difficult to
visualize, but keep in mind that the ROM doesn't care whether
its D0 is really D0, or if its A3 is really A3, etc. As long
as each data line is used as the same D## line for both
programming and reading, and each address line is used as the
same A## for both programming and reading, the ROM will
function properly and the 68000 will see the right
instructions. Think about it...
Why bring this up? If you remove the ROM from the cartridge
PCB and try to read it with a EPROM programmer, there may be
situations where you won't see valid 68000 instructions, or
things won't be in the right place... Assuming your
programmer isn't messed up, this would be because the address
and data lines on the ROM aren't assigned the way you'd
expect.
Why would someone make a cartridge like this? To make your
life difficult, if you're wanting to hack their ROMs, or to
make their life easy, by making the cartridge PCB easier to
design.
The easiest way to avoid this potential problem is to build
an adapter from your programmer's EPROM socket to an edge
card connector into which you plug the cartridge. This is a
bit safer, too, so you don't have to remove the ROM from the
cartridge (or even open it up).
The Memory Map
--------------
$000000 $3fffff Cartridge ROM, when enabled by cartridge
control register and !CART_IN.
$000000 $0007ff Internal OS ROM, when enabled by cartridge
control register and !CART_IN.
$ff0000 $ffffff 64Kbytes scratchpad RAM
Partially decoded; RAM actually appears repeated between
$e00000 through $ffffff.
$a14101 cartridge control register
bit 0 = 0: cartridge disabled, OS ROM enabled
bit 0 = 1: cartridge enabled, OS ROM disabled
$a00000 $a????? Unknown. Audio? Controller I/O?
$c00000 $c????? Video display controller registers
The OS puts the top of its stack at $ffff00, and defines a
"user stack pointer" at $000000 (building down through the
top of RAM memory).
The Z80 processor is used for sound and has 8Kbytes of RAM.
I don't know anything about how the Z80 does its work, as I
haven't looked.
Acknowledgements
----------------
Thanks to:
dt93tn@pt.hk-r.se (Tore Nestenius) for info on older Genesis
systems.
lewism@rpi.edu (Michael Lewis) for info on the Sony CXA1145
and Samsung KM6264 chips.
crs@crs-sys.uucp (Chris Gregors) for posting a version of the
Genesis cartridge port pinouts.
merlyn@digibd.com (Brian Westley) for Game Genie information
and decoder program.
------------------------------------------------------------
2.2 Joystick - 3 button version - Could some please post a 6
button version?
By: nhowland@matt.ksu.ksu.edu (Neal Howland) for information
on the Joystick port.
First some background info: The chip inside the controller
is a 74HC157. This is a high-speed cmos quad 2-line to
1-line multiplexer. Basically how this works is there are two
inputs ( A and B ) for every output ( Y ). There are four
groups like this. There is one select signal for the whole
chip. When the select signal is low, the output ( Y ) is the
same as input A. When the select signal is high, the output
Y is the same as input B. The pinout for the chip is as
follows:
Pin 1 - SelectPin 16 - Vcc (+5V)
Pin 2 - 1APin 15 - G (? must be low)
Pin 3 - 1BPin 14 - 4A
Pin 4 - 1YPin 13 - 4B
Pin 5 - 2APin 12 - 4Y
Pin 6 - 2BPin 11 - 3A
Pin 7 - 2YPin 10 - 3B
Pin 8 - GndPin 9 - 3Y
All the controls are done with switches. Up is a switch,
Down is a switch, etc. Now, I will be referring to the output
of these switches later on. What I mean is that the output is
usually high, that is when the switch isn't pressed.
When the button is pushed, the output goes low. This is
accomplished by connecting the output to +5V through a 10k
resistor. The button is then attached between the output and
ground. It looks like this:
+5V -----/\/\/------+--------- Output
10k |
|
/ |
Ground -----/ -------+
button
(normally open)
For all of those who could actually decipher the above
schematic, congratulations!
I will now run down what lines from the plug are connected to
what. The line numbers are determined as follows, looking
straight at the plug on the front of the Genesis the numbers
are:
1 2 3 4 5
6 7 8 9
(For those of you who buy a joystick cable from radio shack
the pin #'s to wire colors are as follows: 1-white 2-blue
3-green 4-brown 5-yellow 6-orange 7-red 8-black 9-gray )
anyway, line connections:
Line 1 - Up output These are the only two direct
Line 2 - Down output connections
Line 3 - Pin 4 of the chip output 1Y
Line 4 - Pin 7 of the chip output 2Y
Line 5 - This line carries in +5V. It is connected to the
+5V bus line.
Line 6 - Pin 9 of the chip output 3Y
line 7 - Pin 1 of the chip this carries in a select signal
from the Genesis. This is a signal which varies
rapidly and controls which input goes through the
output.
Line 8 - Ground This is connected to the Ground bus line.
Line 9 - Pin 12 of the chip output 4Y
Now for the chips pin connections:
Pin 1 - Line 7 (select)
Pin 2 - Ground (1A) Don't ask me why they do this. Maybe
Pin 3 - Left (1B) future expansion
Pin 4 - Line 3 (1Y)
Pin 5 - Ground (2A) Again, possibly future expansion
Pin 6 - Right (2B)
Pin 7 - Line 4 (2Y)
Pin 8 - Ground (GND)
Pin 9 - Line 6 (3Y)
Pin 10 - Button B (3B)
Pin 11 - Button A (3A)
Pin 12 - Line 9 (4Y)
Pin 13 - Button C (4B)
Pin 14 - Start (4A)
Pin 15 - Ground (G) This must be connected to ground
Pin 16 - +5V (Vcc) Power source for the chip
Anyway that's all the info needed to build your own joystick.
Now as an added bonus, additional information!
A simple source for a joystick cable is the Radio Shack
joystick extension cable. It is around $5 and is 10 ft. long.
Just snip off the connector that won't plug into the Genesis,
strip the wires back, and use the color pinout list I gave
above.
I went to my local arcade game repair company today and
purchased the supplies I needed. They were much cheaper than
I expected. Things you would need to buy from them would be:
an 8-way joystick this ran me $15
3 buttons $2.50 apiece
I only bought three buttons because I am going to use a Radio
Shack push button switch for my start button. You can purchase
4 arcade game buttons if you wish.
Interesting ideas for extras on the joystick:
1. Autofire can be achieved with a simple 555 timer circuit.
For anyone wanting a challenge it should be possible to
build a digital autofire using a divide-by-n counter with the
select signal as clock input.
2. Slow down mode is just autofire for the start button.
=============================================================
3.0 Companies - these companies produce the hardware that is
required to write games for the Genesis. The original
document came from: Scott Golby <sgolby@st.nepean.uws.edu.au>
Hi Everyone,
Here is the current list of info I have about the Sega.
I have had about 10 replies so far asking to pass my
info on. If people want I will pass their EMail address on
to everyone else so we can work as a group. Drop me a line
if you want to be added to the 'group' list.
***** <----- Five astrict like this means info from
different people
Sega Genesis Developer Resources
Dan Chang April 18, 1993
Sega of America Inc
Consumer Products Division
125 Shoreway Road
San Carlos, California, 94070
Tel : (415) 802-4400
Fax : (415) 802-4458
Products : Detailed SEGA Genesis technical information. GEMS
SEGA music development package.
Solution : Music and Sound effects package for the Sega. SOA
can provide detailed information on programming the Genesis;
however they will want to know more about your company first.
Western Technologies, Inc.
12057 Jefferson Blvd
Culver City, California, 90230
Tel : (310) 821-7880
Fax : (310) 306-1739
Products : SegaDev Card. PC-Hosted Genesis development
hardware, which includes SEGADEV.EXE, a Windows-hosted
source-level debugger, and SEGALOAD.EXE, a PC_hosted 68000
object code downloader.
Solutions : SEGA Genesis Hardware, WT recommends Sierra
Systems 68000 Assembler.
Sierra Systems
6728 Evergreen Ave
Oakland California 94611
Tel : (510) 339-8200 or (800) 776 4888
Fax : (510) 339 3844
Products : PC-hosted Sierra C cross-compiler, which included
68000 C compiler, assembler, linker.
Motorola, Literature Dist
This entry basically has a list of 68000 reference and
programming books.
Echidna
1101 W Stevens Ave, Suite 232
Santa Ana California 92707
Tel : (714) 545-2662
Fax : (714) 545-3705
Products : tUME - the Universal Map Editor. PC-Hosted tool to
edit tile-maps.
Solutions : Saves time in designing game maps and placing
level information. Downloads maps to Western Techs SegaDev
card.
Cross Products Limited
23 The Calls
Leeds LS2 7EH, England
Tel 0532 429814
Fax 0532 426163 (dial 011 44 532 426163 from USA)
Product : SNASM68K : PC-Hosted SEGA Genesis development
system, which includes a 68000 assembler, linker, debugger.
Parsons Engineering
imhurst Ave
Covina California 91724
Tel (818) 966 5538
Products : PC/Apple IIgs hosted Sluggo Genesis development
hardware.
Advantech
1333 E.9400 South, Suite 160
Sandy Utah, 84092
Tel : (801) 572-5410
Fax : (810) 572-5674
Products : blank SEGA Genesis cartridge PC boards, blank
EPROMS.
*****
Genesis Development System Frequently Asked Questions
Q) What is the Genesis Development System?
A) The GDS is a cross development system that lets you develop
games and other software to run on the Sega Genesis. The
system consists of a 4 inch by 8 inch printed circuit board
that plugs in the cartridge slot of the Genesis, and has a
cable going to the parallel port of the host computer. A
complete software set is included consisting of an
integrated editor/assembler, a stand alone assembler, a
symbolic debugger, a music and sound effect editor, a
utility to break standard 16 color IFF images into tiles to
be downloaded to the Sega, and other files.
Q) Does it come with any source files?
A) You get source to the music editor, source to a Z80 program
to run on the genesis to interpret the music files, source
to a demo program that plays music and has sprites bouncing
around behind the Sega logo, source to the download
utilities. Complete source is provided on communicating
between the host machine and the Genesis.
Q) How much memory does it have on the board?
A) It comes with 1.25 megabytes of memory. 1 meg is intended
for program development and .25 megs is intended for
variable storage for the debugger and scratch memory.
Q) Can you program CD games with it?
A) No, unless you were to write an emulator for the CD rom
that could send data over the normal cable from the host
machine.
Q) Does it include technical specifications for the Genesis?
A) Yes, it comes with descriptions of the memory map, graphics
registers, the Z80's functions, reading the joysticks,
sprites, scrolling, tiles, the DMA copier, the audio chips-
in short everything required to program the genesis. Also
provided is a working demo with source.
Q) Is this proprietary information stolen from Sega?
A) No, the information on the Genesis came from reverse
engineering it, completely independent of Sega. There are
no copyright violations in the purchase or sale of this
development system, nor is there anything illegal about any
use of it.
Q) How does it work?
A) The board has ROMs on it which contain the monitor and
debugger that runs on the Genesis. When the Genesis is
reset, the ROMs take over and wait for commands to come
from the host machine-commands like download bytes, send
bytes back, set up registers, define a symbol, or enter the
interactive debugger. When in the interactive debugger the
host machine acts as a terminal, and characters are sent
over the cable. Full 68000 debugging is possible, including
disassembly, single step, register view and modify,
breakpoints, expression evaluation, memory view, modify,
search and copy, symbol definition, memory compare. There
is also a z80 disassembler built in.
Q) How does the editor work?
A) From within the Amiga version of the editor through single
keys you can assemble your file, move the cursor to errors,
enter the debugger on the Genesis (editor becomes
terminal), download code and data, download code only (for
faster development). The IBM PC version of the editor
provides none of these features. Instead they are invoked
from commands at the CLI.
Q) What about the assembler?
A) The assembler is a full macro 68000 assembler, and includes
the full 8080 and parts of the Z80 instruction set. It
generates symbol table information that can be downloaded
to the Genesis to allow for symbolic debugging. It is quite
fast-on a standard Amiga about 40,000 lines/minute, on a
68030 at 33 Mhz it runs at about 220,000 lines/minute. On a
66 Mhz DX2 the assembler is about 550,000 lines/minute.
Q) Can I program in C?
A) If you have a C compiler that can generate a binary, you
can download it to the Genesis. This system is geared
towards assembly language development, where it really
shines. In the future if there is sufficient demand a C
compiler will be included.
Q) How do I make artwork? Is there a sprite editor?
A) Originally I planned on including a simple graphic editor,
but I found that no one used it-instead they used Dpaint.
The best way is to use dpaint to create graphics in lo-res
16 color mode, then to use the utility I provide to convert
them to raw data to be sent to the Sega. Animation can be
done within Dpaint. Unfortunately there is no editor for
manipulating giant figures made out of sprites, but in
principle it would be possible to do. So probably you will
use dpaint or some other painting program to create the
artwork.
A) Can you backup existing cartridges like the game backup
systems?
Q) No-this system is intended for game development. However if
you were able to obtain ROM images, they can be downloaded
just like original code, and they would run on the system,
keeping in mind the 1.25 megabyte memory limit to the
board. When running a ROM under the system, you can tinker
with memory, modify gameplay, add lives, etc. You can do
all the normal debugging functions, like single step,
breakpoints, etc, to see how the program is working. Making
a cartridge reader requires some hardware expertise, but is
fairly straightforward.
Q) How fast are downloads?
A) Data is transferred a little over 30K/second unless the host
machine is old or slow. That rate is valid for an
accelerated Amiga or a 486, and probably a 386 as well.
There is also a 120K/second transfer capability but there
is no error checking in this mode. Future versions of the
board will have standard rates of 110K/second on a fast PC
and about 100K/second on a fast Amiga.
Q) What host machines is this available on?
A) Currently the complete system is available on the Amiga and
on the IBM PC.
Q) Why should I buy your system and not go through Sega?
A) If you can get Sega to listen to you and you can afford to
pay $$$$$ for their system, then there isn't much advantage
to buying from me. It's been my experience that Sega is
very hard to deal with, and unless you're a big company
they will ignore you. If you buy this system, you don't
need to sign away your future, you don't need to sign any
non-disclosures. You immediately have the ability to create
software for the Genesis. If you create a game, you can
then sell it outright or attempt to publish it yourself-
never having to pay Sega a dime, as they provided you with
nothing and you have no agreement with them. This system
gives you options. Moreover it may be a better system to
develop on that the one Sega provides, but I don't know for
sure as I've never seen theirs-I've just heard rumors.
Q) How long has this system been available?
A) It first became available in April 1991.
Q) How many have already been sold?
A) I've sold around 20 units so far, although I've done no
advertising other than leave a brochure at the 1991 Game
Developer's conference. I haven't really been serious about
marketing it in the last two years. Recently I've posted
some articles on internet and this has resulted in sales of
5 units to three separate groups.
Q) How much does it cost?
A) The cost is $1000.
Q) Will it be ported to other platforms?
A) There are no plans to port the software to any other
platforms.
Q) What about technical support? How about software upgrades?
A) You can send me email and I will answer questions and help
solve your problems. If I'm home you can call me.
Concerning software support: I want you to be happy with
this. If you want some program written, and it seems like a
good idea, chances are I'll do it for free and include it
with the system. Currently if the software seems sparse
it's because no one has complained so I guess I include
enough. There's no point in writing software if it isn't
going to be used. In any case software upgrades are free
unless it's some major upgrade like including a C compiler-
I don't believe in selling something for hundreds of
dollars then nickel and diming you on upgrades. EPROM
upgrades are free if you send back your originals.
Q) Do we need to pay you any royalty on games developed with
the system?
A) No. Once you bought the system you can do anything you want
with it-except copy it and sell it yourself...
Q) Are there future systems in the works? Possibly with more
memory?
A) Eventually a new version of the circuit board will be
finished. This will offer 18 megabits of RAM standard for
the same price as the current board. Some time after that
there will likely be a special 32 meg option. The 32
meg version will cost about $1150-$1200.
Q) If I buy one of the boards and a newer version of the
hardware becomes available later, can I upgrade?
A) Yes. To upgrade to a future version of the hardware you
would send back the old board along with enough money to
pay for manufacture of the new board. To determine the cost
of manufacture, figure a base price of $30 to cover the
printed circuit board and sockets and connectors, plus $15
for the inexpensive logic chips, plus the following amounts
for memory:
8 megabits -> 16 megabits = $100 for memory upgrade
8 megabits -> 32 megabits = $200 for memory upgrade
16 megabits-> 32 megabits = $100 for memory upgrade (you
re-use old chips)
Note that at this time the 16 and 32 megabit versions are
not completed. The current version of the board uses
obsolete RAM chips that cannot be used on the future
versions. The new 16 and 32 megabit versions will use
smaller, more dense, cheaper RAM chips which can be moved
from one board to another.
Q) How can I contact you?
A) Send me mail, email or call.
818-584-0357
INTERNET: dash@netcom.com
David Ashley
395 Sierra Madre Villa
Pasadena, CA 91107
USA
*****
The person you want to talk to at Sega of America is Stuart
Kosoy, at (415)802-4407.
*****
=============================================================
4.0 Code samples. The following code was graciously given to
me by David Ashley, inventor of the GDS. We all owe him a big
Thanks!
Here's sample code for reading the joystick:
------------
;jsinit must be called to set up the joystick, otherwise
;reading back will have errors. This need only be called
;once.
jsinit: moveq #$40,d0
move.b d0,$a10009
move.b d0,$a1000b
move.b d0,$a1000d
rts
;The following two routines can be used for reading from the
;joystick ports.
;porta and portb return a byte in d0. 0 bits mean button is
;not down, 1 mean button is down.
;The order is:
;76543210
;SACBRLDU
;meaning Start, A, C, B, Right, Left, Down, Up
porta: move.b #$40,$a10003
nop
nop
move.b $a10003,d1
andi.b #$3f,d1
move.b #$00,$a10003
nop
nop
move.b $a10003,d0
andi.b #$30,d0
lsl.b #2,d0
or.b d1,d0
not.b d0
rts
portb: move.b #$40,$a10005
nop
nop
move.b $a10005,d1
andi.b #$3f,d1
move.b #$00,$a10005
nop
nop
move.b $a10005,d0
andi.b #$30,d0
lsl.b #2,d0
or.b d1,d0
not.b d0
rts
-----------------------
Graphics code is another matter. Since I sell a development
system, and one of the features is I provide technical info
on the Genesis hardware, it would sort of be a conflict of
interest for me to give things away :^).
-------------------
=============================================================
5.0 Language Switch, from Rec.Games.Video FAQ
How to make a language switch (Genesis/MD).
On a Genesis/MD, there are jumpers labelled JP1, JP2, JP4,
and JP3. The Genesis has a capacitor on JP1 and a trace on
JP2; the Mega Drive has a capacitor on JP2 and a trace on
JP1. The bottom ends of JP1 and JP2 are connected together.
So if you cut the trace and the top end of the capacitor, and
install a DPDT switch between them which reconnects them
either unchanged or swapped left to right, you have a
language switch. You'll need some wire, a soldering iron,
solder, and a DPDT switch.
Some machines have an open circuit instead of the capacitor.
Also, I've been told that even if there is a capacitor, you
can throw it out and leave an open circuit. Either way, the
switch is a lot simpler, requiring a SPDT switch and less
wire and solder.
Several people have told me that you could just cut both JP1
and JP2 and put a SPST switch on JP1. This is even simpler,
but I'm not sure it really works, as opposed to putting your
machine in an intermediate state that only sort-of works.
The redesigned Genesis 2 machines don't appear to have either
the capacitor or circuit. Nobody yet knows how to make the
language switch for one, though there are language switch
cartridges you can buy to act as one.
IF YOUR MACHINE HAS NO CAPACITOR (or if you want to cross
your fingers and throw away your capacitor) and is not a
Genesis 2:
Cut JP2. The trace might be covered with paint and hard to
see. (If you started with a Mega Drive, JP2 is open and you
have to cut JP1 instead.) If you aren't sure which end I mean
by "bottom", just check the back of the board to see which
end is connected together.
Original state of machine: After cutting:
JP2 top JP1 top JP2 top JP1 top
| | | |
| | | |
|
|
|
|
| | | |
\ / \ /
\_______/ \_______/
bottom of both bottom of both
Add a SPDT switch which can be in one of two positions:
._ _ _ _ _ _ _ _ _ _ _ _
. .
. . _ _ _ _ _ _ _ _ _ _
. . . .
JP2 top JP1 top . .
| | . .
| | _________
| o o |
| \ |
| \ |
\___o___/
| | .
\ / .
\_______/ - - - - - - - - - - - -
bottom of both
._ _ _ _ _ _ _ _ _ _ _ _
. .
. . _ _ _ _ _ _ _ _ _ _
. . . .
JP2 top JP1 top . .
| | . .
| | _________
| o o |
| / |
| / |
\___o___/
| | .
\ / .
\_______/ - - - - - - - - - - - -
bottom of both
-------------------------------------------------------------
IF YOUR MACHINE DOES HAVE THE CAPACITOR:
Cut both sides. (Note: if you started with a Japanese Mega
Drive the capacitor will be on the side labelled X instead)
Original state of machine: After cutting:
JP2 top JP1 top JP2 top JP1 top
| | | |
| | | |
| |
| |
| | |
X | ### X | ###
| ### | ###
| ### | ###
\ / \ /
\_______/ \_______/
bottom of both
add switch which can be in one of two positions:
JP2 top JP1 top
(Connect 2 to 2
| |
and 1 to 1)
| |
2 1 2 1 1 2
______________
_ _ _ _ _ _ _ _ _ _ | o o o o |
| ` | \ \ |
X | ###` ` | \ \ |
| ### ` ` \____o__o____/
| ### ` ` ' '
\ / ` `- - - - -' '
\_______/ ` _ _ _ _ _ _ _ _ '
bottom of both
JP2 top JP1 top
(Connect 2 to 2
| |
and 1 to 1)
| |
2 1 2 1 1 2
______________
_ _ _ _ _ _ _ _ _ _ | o o o o |
| ` | / / |
X | ###` ` | / / |
| ### ` ` \____o__o____/
| ### ` ` ' '
\ / ` `- - - - -' '
\_______/ ` _ _ _ _ _ _ _ _ '
bottom of both
50/60 hertz switch.
You can build a 50/60 hertz switch on a Genesis/Mega Drive
like a language switch, but using jumpers JP3 and JP4. The
standard setting is 50 in PAL areas such as Europe, and 60 in
NTSC areas like the US and Japan. In the 60 hertz mode, the
game is faster and the screen taller; however, not all TVs
and monitors in Europe can display this mode.
Some American/Japanese games are protected to keep Europeans
from playing them; this protection checks the 50/60 hertz
setting. You can usually get around it by installing the
switch and switching when starting the game, then switching
back afterwards.
Many European games are simple ports of American or Japanese
games and are not redesigned for 50 hertz, so work faster and
with "better" screen proportions if played at 60 hertz.
Genesis/Mega Drive dual version (language switch) list:
Bonanza Brothers: Game plays in Japanese. (Maybe. There
seems to be more than one version floating around.)
Columns: Game plays in Japanese.
*Cyberball: Japanese version has a modem option.
Dragon's Fury: Works only with language set to English.
The original, Devil's Crush MD, works either way.
Dynamite Duke: Harder on the Mega Drive.
Elemental Master: Harder on the Mega Drive.
Fatal Labyrinth: Game plays in Japanese.
Fire Shark: Different title screen with Kanji.
Flicky: Characters have Japanese names and instructions
are in Japanese.
Forgotten Worlds: Game plays in Japanese.
Gaiares: only mentions the Japanese licensee on the title
screen, and has Japanese text; you can also select
Japanese text from the option screen.
Ghostbusters: Game plays in Japanese.
Ghouls and Ghosts: Different title screen with Kanji. To
see it on a Genesis, select the last music and sound (26
and 56) from the options screen, then press lower left;
A, B, or C; and Start all at the same time. (I never
tried this, but Gamepro magazine claimed it works.) The
game shows some other Japanese text, and when you die
during a boss you start out earlier.
Insector X: Title screen refers to company as Hot-B, not
Sage's Creation. The MD version shoots more slowly. The
ending text is still English.
*Marvel Land: The Japanese version says "for Mega Drive"
or "for Genesis" but the language stays Japanese. (What
does an English version do?)
Monaco GP: Game plays in Japanese (also an option on the
option screen).
Mystic Defender: This game is actually the anime-based
Kujaku-Ou (Peacock King) 2 game. In Japanese mode, the
opening text is replaced by a graphics screen (never
seen in the US version) with Japanese. The levels have
names, the main character wears a white robe, the
lightning magic effect is different, and the character
is named Kujaku in the ending (which is still English).
Outrun: The attract mode lacks sound, the startup screen
says "push" (not "press") start button, and "(C) Sega
1986, 1991" is printed in reverse order. The default
options are KM/H and a different button selection (but
can still be changed on the option screen).
Quackshot: Game plays in Japanese.
Raiden Trad: The "licensed to Sega" line is absent on
both title screens, and the second title screen includes
only the Japanese part instead of the non-Japanese part
of the first one.
Revenge of Shinobi: Title changes to Super Shinobi;
credits show at the end.
Rolling Thunder II: The Japanese version only works on a
Japanese setting. The US version works either way (and
isn't bilingual).
Sonic the Hedgehog II: Tails is renamed to "Miles".
Streets of Rage: Title screen changes to Bare Knuckle,
and all text is in Japanese, including the introduction.
The clock resets when you encounter the bosses.
Streets of Rage II: Turns to Bare Knuckle II, and renames
Skate to Sammy --_if_ you change the setting sometime
after turning the machine on (to skip the lockout).
Thunder Force II: Title screen has "MD" on it, and
company name is "Tecnosoft".
Thunder Force III: company's name is spelled "Tecnosoft".
*Thunder Storm FX (CD): Turns to Cobra Command in US mode.
Truxton: Japanese title is Tatsujin.
Twin Hawk: Different title screen with Kanji.
*Wrestle War: The wrestler is blond on a Genesis and
black-haired on a MD.
* Information from testing a Japanese game
=============================================================
I hope to get more information and expand this document.
Please E-Mail me for a copy or to add information to this
list. Again My E-Mail address is
U6c16@Wvnvm.Wvnet.Edu
SnailMail:
Henry Rieke
Attn: Sega FAQ
161 Poplar Dr
Morgantown, Wv 26505-2340
A Very Special Thanks to:
David Ashley <dash@netcom.com>
Special Thanks to :
Scott Golby <sgolby@st.nepean.uws.edu.au>
Rick McTeague <sysrick@starbase.spd.louisville.edu>
Neal Howland <nhowland@matt.ksu.ksu.edu>
#
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