JOYxDAT

         These addresses each read a 16 bit register. These in turn
         are loaded from the MDAT serial stream and are clocked in on
         the rising edge of SCLK. MLD output is used to parallel load
         the external parallel-to-serial converter.This in turn is
         loaded with the 4 quadrature inputs from each of two game
         controller ports (8 total) plus 8 miscellaneous control bits
         which are new for LISA and can be read in upper 8 bits of
         LISAID.


         For Mouse:  (pins  1,3 =Yclock, pins 2,4 =Xclock)


    BIT#  15  14  13  12  11  10  09  08     07  06  05  04  03  02  01  00
JOY0DAT   Y7  Y6  Y5  Y4  Y3  Y2  Y1  Y0     X7  X6  X5  X4  X3  X2  X1  X0
JOY1DAT   Y7  Y6  Y5  Y4  Y3  Y2  Y1  Y0     X7  X6  X5  X4  X3  X2  X1  X0


         0=LEFT CONTROLLER PAIR, 1=RIGHT CONTROLLER PAIR.
         (4 counters total).The bit usage for both left and right
         addresses is shown below. Each 6 bit counter (Y7-Y2,X7-X2) is
         clocked by 2 of the signals input from the mouse serial
         stream. Starting with first bit recived:


         +-------------------+-----------------------------------------+
         | Serial | Bit Name | Description                             |
         +--------+----------+-----------------------------------------+
         |   0    | M0H      | JOY0DAT Horizontal Clock                |
         |   1    | M0HQ     | JOY0DAT Horizontal Clock (quadrature)   |
         |   2    | M0V      | JOY0DAT Vertical Clock                  |
         |   3    | M0VQ     | JOY0DAT Vertical Clock  (quadrature)    |
         |   4    | M1V      | JOY1DAT Horizontall Clock               |
         |   5    | M1VQ     | JOY1DAT Horizontall Clock (quadrature)  |
         |   6    | M1V      | JOY1DAT Vertical Clock                  |
         |   7    | M1VQ     | JOY1DAT Vertical Clock (quadrature)     |
         +--------+----------+-----------------------------------------+


         For Joystics:


         Bits 1 and 0 of each counter (Y1-Y0,X1-X0) may be
         read to determine the state of the related input signal pair.
         This allows these pins to double as joystick switch inputs.
         Joystick switch closures can be deciphered as follows:


         +------------+------+---------------------------------+
         | Directions | Pin# | Counter bits                    |
         +------------+------+---------------------------------+
         | Forward    |  1   | Y1 xor Y0 (BIT#09 xor BIT#08)   |
         | Left       |  3   | Y1                              |
         | Back       |  2   | X1 xor X0 (BIT#01 xor BIT#00)   |
         | Right      |  4   | X1                              |
         +------------+------+---------------------------------+


         For Paddles:


          1           Right paddle fire button (1 = fire)
          9           Left paddle fire button  (1 = fire)