2 ; Standard joystick driver for the VIC20. May be used multiple times when linked
3 ; to the statically application.
5 ; Ullrich von Bassewitz, 2002-12-20
6 ; Using code from Steve Schmidtke
9 .include "zeropage.inc"
11 .include "joy-kernel.inc"
12 .include "joy-error.inc"
19 ; ------------------------------------------------------------------------
20 ; Header. Includes jump table
22 module_header _vic20_stdjoy_joy
26 .byte $6A, $6F, $79 ; "joy"
27 .byte JOY_API_VERSION ; Driver API version number
39 .addr 0 ; IRQ entry unused
41 ; ------------------------------------------------------------------------
44 JOY_COUNT = 1 ; Number of joysticks we support
47 ; ------------------------------------------------------------------------
53 ; ------------------------------------------------------------------------
54 ; INSTALL routine. Is called after the driver is loaded into memory. If
55 ; possible, check if the hardware is present and determine the amount of
57 ; Must return an JOY_ERR_xx code in a/x.
63 ; rts ; Run into UNINSTALL instead
65 ; ------------------------------------------------------------------------
66 ; UNINSTALL routine. Is called before the driver is removed from memory.
67 ; Can do cleanup or whatever. Must not return anything.
74 ; ------------------------------------------------------------------------
75 ; COUNT: Return the total number of available joysticks in a/x.
83 ; ------------------------------------------------------------------------
84 ; READ: Read a particular joystick passed in A.
85 ; The current implemenation will ignore the joystick number because we do only
88 READ: lda #$7F ; mask for VIA2 JOYBIT: sw3
89 ldx #$C3 ; mask for VIA1 JOYBITS: sw0,sw1,sw2,sw4
92 ldy VIA2_DDRB ; remember the date of DDRB
93 sta VIA2_DDRB ; set JOYBITS on this VIA for input
94 lda VIA2_JOY ; read JOYBIT: sw3
95 sty VIA2_DDRB ; restore the state of DDRB
96 asl ; Shift sw3 into carry
98 ldy VIA1_DDRA ; remember the state of DDRA
99 stx VIA1_DDRA ; set JOYBITS on this VIA for input
100 lda VIA1_JOY ; read JOYBITS: sw0,sw1,sw2,sw4
101 sty VIA1_DDRA ; restore the state of DDRA
104 php ; Save sw3 in carry
105 lsr ; Shift sw0,sw1,sw2,sw4 into bits 1-4
106 tax ; Save sw0,sw1,sw2
107 and #$10 ; Extract sw4 in bit 4
108 sta tmp1 ; Save sw4 in bit 4
109 txa ; Restore sw0,sw1,sw2
110 lsr ; Shift sw0,sw1,sw2 into bits 0-2
111 and #$07 ; Mask bits 0-2
112 plp ; Restore sw3 in carry
113 bcc @L0 ; Is sw3 set?
114 ora #$08 ; Yes: Add sw3 in bit 3
115 @L0: ora tmp1 ; Add sw4 in bit 4
116 eor #$1F ; Active states are inverted