JOY0DAT 00A R D Joystick-mouse 0 data (left vertical, horizontal)
JOY1DAT 00C R D Joystick-mouse 1 data (right vertical, horizontal)
These addresses each read a pair of 8-bit mouse counters. 0=left
controller pair, 1=right controller pair (four counters total). The bit
usage for both left and right addresses is shown below. Each counter is
clocked by signals from two controller pins. Bits 1 and 0 of each counter
may be read to determine the state of these two clock pins. This allows
these pins to double as joystick switch inputs.
Mouse counter usage:
(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
----------------------------------------------------
0DAT Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 X7 X6 X5 X4 X3 X2 X1 X0
1DAT Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0 X7 X6 X5 X4 X3 X2 X1 X0
The following Table shows the mouse/joystick connector pin usage. The
pins (and their functions) are sampled (multiplexed) into the DENISE chip
during the clock times shown in the Table. This Table is for reference
only and should not be needed by the programmer. (Note that the joystick
functions are all "active low" at the connector pins.)
Sampled by DENISE
Conn Joystick Mouse
Pin Function Function Pin Name Clock
------------------------------------------------
L1 FORW* Y 38 M0V at CCK
L3 LEFT* YQ 38 M0V at CCK*
L2 BACK* X 9 M0H at CCK
L4 RIGH* XQ 9 M0H at CCK*
R1 FORW* Y 39 M1V at CCK
R3 LEFT* YQ 39 M1V at CCK*
R2 BACK* X 8 M1H at CCK
R4 RIGH* XQ 8 M1H at CCK*
After being sampled, these connector pin signals are used in quadrature
to clock the mouse counters. The LEFT and RIGHT joystick functions
(active high) are directly available on the Y1 and X1 bits of each
counter. In order to recreate the FORWARD and BACK joystick functions,
however, it is necessary to logically combine (exclusive OR) the lower
two bits of each counter. This is illustrated in the following Table.
TO DETECT READ THESE COUNTER BITS
----------------------------------------------------------
Forward Y1 xor Y0 (BIT#09 xor BIT#08)
Left Y1
Back X1 xor X0 (BIT#01 xor BIT#00)
Right X1
- Appendix A 275 -
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