Latest revision as of 11:53, 19 January 2017

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

1

Bit	7	6	5	4	3	2	1	0
Def	0	TH	C	B	RIGHT	LEFT	DOWN	UP

0

Bit	7	6	5	4	3	2	1	0
Def	0	TH	START	A	0	0	DOWN	UP

Code

 	moveq	#0, d0
	moveq	#0, d1

	move.b  #0x40, (0xA10009)	| Set direction
	move.b  #0x40, (0xA10003)	| TH = 1
	nop
	nop
	move.b  (a0), d0		| d0.b = X | 1 | C | B | R | L | D | U |
	andi.b	#0x3F, d0		| d0.b = 0 | 0 | C | B | R | L | D | U |

	move.b	#0x0, (0xA10003)	| TH = 0
	nop
	nop
	move.b	(0xA10003), d1		| d1.b = X | 0 | S | A | 0 | 0 | D | U |
	andi.b	#0x30, d1		| d1.b = 0 | 0 | S | A | 0 | 0 | 0 | 0 |
	lsl.b	#0x2, d1		| d1.b = S | A | 0 | 0 | D | U | 0 | 0 |
	or.b	d1, d0			| d0.b = S | A | C | B | R | L | D | U |

@@ Line 15: / Line 15: @@
 |'''Data'''
 |-
-|0
+|1
 |{{8BitRegister
-|?|0
+|0|0
 |TH|1
-|START|1
+|C|1
-|A|1
+|B|1
-|0|1
+|RIGHT|1
-|0|1
+|LEFT|1
 |DOWN|1
 |UP|1
 }}
 |-
-|1
+|0
 |{{8BitRegister
-|?|0
+|0|0
 |TH|1
-|C|1
+|START|1
-|B|1
+|A|1
-|RIGHT|1
+|0|1
-|LEFT|1
+|0|1
 |DOWN|1
 |UP|1
@@ Line 42: / Line 42: @@
 =Code=
-<syntaxhighlight>
+<syntaxhighlight lang="asm">
-    move.b  #0x40, (0xA10009)        ; Set the direction
+ 	moveq	#0, d0
-    nop
+	moveq	#0, d1
-    nop
-    move.b  #0x40, (0xA10003)        ; Set TH to 1
+	move.b  #0x40, (0xA10009)	| Set direction
-    nop
+	move.b  #0x40, (0xA10003)	| TH = 1
-    nop
+	nop
-    move.b  (0xA10003), d0           ; Read C/B/RIGHT/LEFT/DOWN/UP
+	nop
-    andi.b  #0x3F, d0                ; Discard bit 6 and 7
+	move.b  (a0), d0		| d0.b = X | 1 | C | B | R | L | D | U |
-    move.b  #0x00, (0xA10003)        ; Set TH to 0
+	andi.b	#0x3F, d0		| d0.b = 0 | 0 | C | B | R | L | D | U |
-    nop
-    nop
+	move.b	#0x0, (0xA10003)	| TH = 0
-    move.b  (0xA10003), d1           ; Read START/A
+	nop
-    lsl.b   #0x2, d1                 ; Move START and A to bit 6 and 7
+	nop
-    andi.b  #0xC0, d1                ; Only keep START and A
+	move.b	(0xA10003), d1		| d1.b = X | 0 | S | A | 0 | 0 | D | U |
-    or.b    d1, d0                   ; Now d0 contain START,A,B,C,RIGHT,LEFT,DOWN,UP (active low)
+	andi.b	#0x30, d1		| d1.b = 0 | 0 | S | A | 0 | 0 | 0 | 0 |
+	lsl.b	#0x2, d1		| d1.b = S | A | 0 | 0 | D | U | 0 | 0 |
+	or.b	d1, d0			| d0.b = S | A | C | B | R | L | D | U |
 </syntaxhighlight>
+[[Category:MegaDrive]]
 [[Category:Code]]

Reading MD3 Joypad: Difference between revisions

Latest revision as of 11:53, 19 January 2017

Details

Code

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