   
                             The Multiplayerdevice

                            (c) 1996 Carsten Schulz



Introduction

As the title says... this text file describes how to build your 
own Multi Port Board for MASTER BLASTER II.(and soon other games)
With it up to 8 (perhaps more in future) players can play at the 
same time. The board is connected to the parallel port an shares
digital joysticks...




1. Schematic


There is a schematic file that comes with this text (MULTI.GIF).
Please print it prior to continue reading!!

The schematic decribes everything necessary for ONE CHANNEL.

Numbers in circles mean pin numbers of IC's or connectors.

Let's start with the power supply because there is not much said about it 
in the schematic. You need a constant voltage supply (5V). Please do NOT
use any unregulated supplies. The source voltage of our circuit may only 
vary within 10%!!! So do use a regulator IC such as 7805.


Ok. Now we go over to the joystick connector. It is a DB9/M. This means 
a connector with 9 male pins.
The functions we need are :

   - Up
   - Down
   - Left
   - Right 
   - Fire

So we need 5 data bits which are x1..x5. Also we need +5V (Vcc) for the 
joystick to switch.

PIN 
1	X1
2	X2
3	X3
4	X4
6	X5
8	Vcc=5V

all others : not connected


These 5 bits go to the inputs of the 74LS367 with one 1k Ohm resistor against
gnd each.

Input pins are 14,12,10,6,4
Corresponding Out's are 13,11,9,7,5
PIN 
1	G1
2	NC	
3	NC	
4	X1
5	D1
6	X2
7	D2
8	GND
9	D3
10	X3	
11	D4
12	X4
13	D5
14	X5
15	G2
16	Vcc



Pins 1 and 15 are Selector Bits. If their level is low, the drivers put their 
input signal on the output. If their level is high, the drivers are high ohm.

So if we have 8 74LS367 on a board, we can select one by lowering it's level 
on pin 1 and 15 and by that read out the input values of the joystick..

The output pins directly go to the DB25 Connector of the parallel port.

PIN 
2	Select Joystick 1 (-> connected to G1,G2 of first IC)  
3	Select Joystick 2 (-> connected to G1,G2 of second IC)
4         "	  "     3
5	  .
6	  .
7         . 
8         .  
9         "       "     8
10 D1
12 D3
13 D5
15 D4
16 D2
18 GND (<- not mentioned in schematic !!!!! Please add this GND line to cable)


all other pins : not connected



2. How it works

The Port (and joystick) is chosen by those bits at pins 2-9 of DB25. The 
software choses only one port at the time of course.
All others have high out impedance. So their joystick signals stay within
the corresponding ICs. The selected IC puts it's information on the bus 
(Data signals D1..D5) to be read out by the pc. Then the other ports are read
one by one.



3. Problems???
If you encounter any problems in understanding the circuit or building it or
whatever you can contact me via Fax at : ++49-2374-169092
(you can also buy complete soldered boards)



So thats it from me!


Have fun with MASTER BLASTER II !!!!!!
 
