Routines
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63293: Read Control Fuller
Control mode 4: reads the Fuller Box joystick port 127 (active- high bits; fire is at bit 7) and remaps direction and fire bits to the game's active-low format.
Read_Control_Fuller 63293 IN A,(127) Read from the joystick;
Port Number Bit
0 1 2 3 4
127 UP DOWN LEFT RIGHT -
63295 OR %01110000 Mask to the relevant direction bits.
63297 LD B,A Save the raw input and rotate one position.
63298 RLCA
63299 OR %11111000 Force the upper five bits high.
63301 LD C,A Save the rotated result.
63302 LD A,B Reload the raw input.
63303 OR %11110111 Isolate bit 3 from the raw input.
63305 AND C Merge with the rotated result.
63306 LD C,A Save the combined result.
63307 LD A,B Reload the raw input.
63308 OR %11111011 Isolate bit 2 from the raw input.
63310 RLCA Shift the bit into position.
63311 RLCA
63312 AND C Merge with the combined result.
63313 RET Return to Read_Control_Input_Return.
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