4in1 Pac-man = Hack

Overview

I am =
a big fan of multigame kits that run on =
original hardware.  For my Pac-man I use Mike Doyle and Dave Widel=92s 96-in-1 kit

located at http://home.everestkc.net/mdoyle/multipac.htm.  =
Like most collectors I come across a number of Pac-man boards =

for projects and can not afford one of =
these kits for each of them.  For these boards I use the free hack located at

http://www.marvin3m.com/video/pacman.htm#hack1. =
 This is a great quick hack for getting more than one version of Pac-man =

on a board.  The only thing I =
don=92t like about this hack is the use of mechanical switches.  =
Generally you need to run some wires

from =
the Pac-man board to the coin door or some other reachable =
location.  My goal when starting this project was to have this =

hack menu driven and eliminate the =
mechanical switches.

Design

The first thing I needed to do was find =
somewhere on the Pac-man board I could control via code to replace the =
mechanical switches.

Looking through the many =
Pac-man resources on the internet I found that the latch at 8K has three =
outputs which it does not use.

The =
addressable latch at 8K that controls sound, flip and other things also =
has output for Start Lamp 1 (Pin 9), Start Lamp 2 (Pin 10) =

and Coin Lockout (Pin 11).  These =
pins can be turned on and off like switches and since Pac-man does not =
use start lamps or the coin

lock-out it is not taking =
anything away from the original game.

I realized after playing =
around with my theory that there was a problem.  When Pac-man =
starts up it clears all the pins on the latch.

In =
fact it clears and sets them a few times during initialization.  =
So, now I needed to go and modify the Pac-man and Ms. Pac-man =

code to get rid of this step or the game =
will reset the first time the latch is cleared.

Next I needed a menu to drive the 4 =
games. My wife helped me design the menu (see below).  It is =
nothing fancy but it will get the

job =
done.  I am sure I will make modification to make it more fancy in the future but this is it for =
now.

After =
getting the menu written and modifying Pac-man code and changing around =
the hack to use the latch instead of the mechanical

switches I =
ran into another issue.  It appears that when the pins would =
turn on to change the bank on the EPROM the CPU would crash =

because it had the code pulled out from =
under it.  I did not realize this at first so I hacked around on =
the board to use transistors,

capacitors, relays and lots =
of other components I did not need.  After chatting with some =
people who have done this before

(see thank you section) it =
turns out that when the bank changes the code on the next line is =
different than expected so the CPU crashes.

To do =
this I needed to make sure that the part of the menu code that turned =
the pins on the latch on and off needed to be in each bank =

of the EPROM at the same location.  =
To do this without removing one of the games I needed to embed some menu =
code into the Pac-man code.

Modified Hack

This is a modified copy of =
the hack from (http://www.marvin3m.com/video/pacman.htm#hack1) that =
uses the 3 pins at 8k

instead of the mechanical =
switches.  My hack uses a 27020 instread of a 27010 which basically have =
the same pinout, but

The 27020 is twice as big.  =
This way I can add my menu and have room to expand it and add a game or =
two later.

Row 6 = mod.
The 27020 is a 32 pin DIP. The socket I used = was 6J and=20 is 24 pins. Bend up pins 1, 2, 3, 4, 22, 24, 25, 28, 29, 30
,31, and 32. Place the new ROM socket in the =
pcb socket so that = the bottom=20 of the chip (opposite side from the notch) lines up with the bottom = of the=20 socket. This means that pin 16 of the chip should go into pin 12 of = the=20 socket. If you had not bent up pins 1 through 4 and pins 29 through = 32,=20 they'de be = hanging off.=20 The actual pcb socket you=20 use isn't important (as long as it's not 6K or 6L). We could = use 6E,=20 6F, or 6H, but the daughterboard in 6D gets in the way. =
1. Connect pins 24 = (OE\) and 22=20 (CE\) to 7N pin 12.
2. Connect pin 25 = (A11) to 7L=20 pin 9.
3. Connect pin 28 = (A13) to 7N=20 pin 14.
4. Connect pin 29 = (A14) to 6B=20 pin 5 (test connector 8th "finger" from the bottom component = side). I=20 tapped into it at this side edge connector.
5. Connect pin 4 = (A12) to 7J=20 pin 6.
6. Solder the wire = between pins=20 1 (Vpp), 31 (PGM\), and 32 (Vcc) to +5 volts. You can tap into this in a = number of=20 places. Pin 24 of every ROM socket has 5 volts on it. =
7. NEW: Connect pin 3 = (A15) to 8K=20 pin 11.
8. NEW: Connect pin 2 = (A16) to 8K=20 pin 10.
9. NEW: Connect pin 30 = (A17) to 8K=20 pin 9

Row 5 = mod.
The 27128 is a = 28 pin DIP.=20 Bend up pins 1, 2, 20, 22, 23, 26, 27, and 28 on a 28 pin socket. = Put the=20 new socket into the pcb=20 socket at 5E or 5F. Again, it doesn't matter which. =
1. Connect pins 22 = (OE\) and 20=20 (CE\) to GND. You can pick up GND at pin 12 of any of the ROM = sockets. You=20 can also use pin 14 of the 27128 or pin 16 of the 27010. GND is = always the=20 top right pin of the EPROM (if you are facing the component side = of the=20 pcb with = the edge=20 connector towards the ceiling).
2. Connect pin 23 = (A11) to 4F=20 pin 1.
3. Connect pin 26 = (A13) to pin=20 2 of the 27010.
4. Connect pin 2 = (A12) to 5L=20 pin 5.
5. Connect pins 1 = (Vpp), 27 (PGM\), and 28 (Vcc) to +5 volts. I just connected pin 1 to = pin 28. I=20 then globbed solder between pins 27 = and 28.=20 Then, I soldered another wire from the glob to pin 24 of another = ROM=20 position (5H).

Modified Eproms

          The row =
6 27c010 EPROM needed to change a bit, but the row 5 EPROM remains =
unchanged.  The row 6 EPROM has

	a new layout to include the menu and some other changes to the =
original Pac-man/Ms. Pac-man code.  This is very

          wasteful, but I did not want to =
make a bunch of changes to fit everything on the 27c010.  The 27c020 =
gives me more

          =
then enough room.

          Download =
bin files: 4n1hack.zip

00000 - 00FFF Menu Part =
1

01000 - 01FFF Menu Part =
1

02000 - 02FFF Menu Part =
2

03000 - 03FFF empty

04000 =
- 04FFF empty

05000 - 05FFF empty

06000 =
- 06FFF empty

07000 - 07FFF empty

08000 - 08FFF Pac-Man 6e

09000 =
- 09FFF Pac-Man 6f speedup cheat

0A000 - 0AFFF Pac-Man 6h / =
Menu Part 2

0B000 - 0BFFF Pac-Man 6j =

0C000 - 0CFFF empty

0D000 =
- 0DFFF empty

0E000 - 0EFFF empty

0F000 =
- 0FFFF empty

10000 =
- 10FFF Ms. Pac-Man boot1

11000 - 11FFF Ms. Pac-Man =
boot2

12000 - 12FFF Ms. Pac-Man boot3 cheat / =
Menu Part 2

13000 - 13FFF Ms. Pac-Man =
boot4

14000 - 14FFF Ms. Pac-Man =
boot5

15000 - 15FFF Ms. Pac-Man =
boot6

16000 - 16FFF empty

17000 =
- 17FFF empty

18000 =
- 18FFF Ms. Pac-Man boot1

19000 - 19FFF Ms. Pac-Man =
boot2 speedup cheat

1A000 =
- 1AFFF Ms. Pac-Man boot3 / Menu Part 2

1B000 =
- 1BFFF Ms. Pac-Man boot4

1C000 - 1CFFF Ms. Pac-Man =
boot5

1D000 - 1DFFF Ms. Pac-Man =
boot6

1E000 - 1EFFF empty

1F000 =
- 1FFFF empty

20000 - 00FFF Pac-Man 6e

21000 - 01FFF Pac-Man 6f cheat

22000 - 02FFF =
Pac-Man 6h / Menu Part =
2

23000 - 03FFF =
Pac-Man 6j

24000 - 04FFF =
empty

25000 - 05FFF =
empty

26000 - 06FFF =
empty

27000 - 07FFF =
empty

Limitations

There are a couple of =
limitations with version 1.0 of the menu.  First, there is no way =
as of yet to return to the menu.

When =
you want to play a different game you need to reset or power off the =
game.  I hope to add this enhancement in

version 2.0 but it means changing more Pac-man code (or areas =
inside the Pac-man code).  Another limitation is there =

are only 4 games.  I don=92t really =
have any plans to add more to this or do a =93real=94 multigame.  This was a fun hack for =

me to do and this is as far as I will =
take it other than updating the menu and maybe add another game or two =
that I

develop.  The only reason I did this =
was to learn and get myself a hack without =
switches.

Thank You

First =
of all thank you to the person or people that came up with the original =
hack.  I would also like to thank the people

who =
helped me with all the great knowledge they have learned and shared via =
a website or emails with me directly.

This =
would not have been possible without Rob Carroll, Sean Riddle, Scott =
=93Jerry=94 Lawrence, David Caldwell and

many =
others.