(See Figure 4-13)
Both the left and right player START/SHOOT/JUMP switches and the left and right Trak Ball horizontal rate of turn information are read by the microprocessor on data lines DBUSO thru DBUS3. The left and right Trak Ball vertical rate of turn information and vertical and horizontal direction of both Trak Balls are read by the MPU on data lines DBUS4 thru DBUS7.
Signals from the address decoder determine which signals are read by the MPU. When LD1 and LD2 are both low. the MPU reads both the player START/JUMP/ SHOOT switches and the horizontal and vertical direction of turn of both Trak Balls. When LD1 is low and LD2 is high, the MPU reads the left and right Trak Ball horizontal rate from counters J9 and J10. When LD1 and LD2 are both high, the MPU reads the left and right Trak Ball vertical rate from counters H9 and H10.
The two coin switches, the TEST switch, the TEST STEP switch (used only during manufacturing), the SLAM switch and VBLANK are all read by the MPU through tristate buffers Fll. The MPU accesses this information via address decode 1N02.
The option switch toggles of J11 are all read by the MPU through tristate buffers Hll. The MPU accesses this information via address decode 1N03.
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