Reading MD3 Joypad: Difference between revisions
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(Created page with "=Details= All the buttons can't be read at once. There is a multiplexer inside the control pad. Reading the 3 buttons pad consist of 5 steps : *Set the direction of pin 6 t...") |
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or.b d1, d0 ; Now d0 contain START,A,B,C,RIGHT,LEFT,DOWN,UP (active low) | or.b d1, d0 ; Now d0 contain START,A,B,C,RIGHT,LEFT,DOWN,UP (active low) | ||
</syntaxhighlight> | </syntaxhighlight> | ||
[[Category:MegaDrive]] | |||
Revision as of 14:27, 20 March 2012
Details
All the buttons can't be read at once. There is a multiplexer inside the control pad.
Reading the 3 buttons pad consist of 5 steps :
- Set the direction of pin 6 to output and all others to input.
- Set TH (pin6) to 1.
- Read the first part of the buttons (UP,DOWN,LEFT,RIGHT,B,C)
- Switch the outputs in the control pad by setting TH (pin6) to 0.
- Read the second part of the buttons (A,START)
| TH State | Data | |||||||||||||||||
| 0 |
| |||||||||||||||||
| 1 |
| |||||||||||||||||
Code
move.b #0x40, (0xA10009) ; Set the direction
nop
nop
move.b #0x40, (0xA10003) ; Set TH to 1
nop
nop
move.b (0xA10003), d0 ; Read C/B/RIGHT/LEFT/DOWN/UP
andi.b #0x3F, d0 ; Discard bit 6 and 7
move.b #0x00, (0xA10003) ; Set TH to 0
nop
nop
move.b (0xA10003), d1 ; Read START/A
lsl.b #0x2, d1 ; Move START and A to bit 6 and 7
andi.b #0xC0, d1 ; Only keep START and A
or.b d1, d0 ; Now d0 contain START,A,B,C,RIGHT,LEFT,DOWN,UP (active low)