1 /***************************************************************************
2
3 This sound driver is used by the Scramble, Super Cobra and Amidar drivers.
4
5 ***************************************************************************/
6
7
8 #include "driver.h"
9 #include "cpu/z80/z80.h"
10
11
12
13 /* The timer clock which feeds the upper 4 bits of */
14 /* AY-3-8910 port A is based on the same clock */
15 /* feeding the sound CPU Z80. It is a divide by */
16 /* 5120, formed by a standard divide by 512, */
17 /* followed by a divide by 10 using a 4 bit */
18 /* bi-quinary count sequence. (See LS90 data sheet */
19 /* for an example). */
20 /* */
21 /* Bit 4 comes from the output of the divide by 1024 */
22 /* 0, 1, 0, 1, 0, 1, 0, 1, 0, 1 */
23 /* Bit 5 comes from the QC output of the LS90 producing a sequence of */
24 /* 0, 0, 1, 1, 0, 0, 1, 1, 1, 0 */
25 /* Bit 6 comes from the QD output of the LS90 producing a sequence of */
26 /* 0, 0, 0, 0, 1, 0, 0, 0, 0, 1 */
27 /* Bit 7 comes from the QA output of the LS90 producing a sequence of */
28 /* 0, 0, 0, 0, 0, 1, 1, 1, 1, 1 */
29
30 static int scramble_timer[10] =
31 {
32 0x00, 0x10, 0x20, 0x30, 0x40, 0x90, 0xa0, 0xb0, 0xa0, 0xd0
33 };
34
READ_HANDLER(scramble_portB_r)35 READ_HANDLER( scramble_portB_r )
36 {
37 /* need to protect from totalcycles overflow */
38 static int last_totalcycles = 0;
39
40 /* number of Z80 clock cycles to count */
41 static int clock;
42
43 int current_totalcycles;
44
45 current_totalcycles = cpu_gettotalcycles();
46 clock = (clock + (current_totalcycles-last_totalcycles)) % 5120;
47
48 last_totalcycles = current_totalcycles;
49
50 return scramble_timer[clock/512];
51 }
52
53
54
WRITE_HANDLER(scramble_sh_irqtrigger_w)55 WRITE_HANDLER( scramble_sh_irqtrigger_w )
56 {
57 static int last;
58
59
60 if (last == 0 && (data & 0x08) != 0)
61 {
62 /* setting bit 3 low then high triggers IRQ on the sound CPU */
63 cpu_cause_interrupt(1, Z80_IRQ_INT);
64 }
65
66 last = data & 0x08;
67 }
68
WRITE_HANDLER(hotshock_sh_irqtrigger_w)69 WRITE_HANDLER( hotshock_sh_irqtrigger_w )
70 {
71 cpu_cause_interrupt(1, Z80_IRQ_INT);
72 }
73
74
filter_w(int chip,int channel,int data)75 static void filter_w(int chip, int channel, int data)
76 {
77 int C;
78
79
80 C = 0;
81 if (data & 1) C += 220000; /* 220000pF = 0.220uF */
82 if (data & 2) C += 47000; /* 47000pF = 0.047uF */
83 set_RC_filter(3*chip + channel,1000,5100,0,C);
84 }
85
WRITE_HANDLER(scramble_filter_w)86 WRITE_HANDLER( scramble_filter_w )
87 {
88 filter_w(1, 0, (offset >> 0) & 3);
89 filter_w(1, 1, (offset >> 2) & 3);
90 filter_w(1, 2, (offset >> 4) & 3);
91 filter_w(0, 0, (offset >> 6) & 3);
92 filter_w(0, 1, (offset >> 8) & 3);
93 filter_w(0, 2, (offset >> 10) & 3);
94 }
95