1 /*****************************************************************************
2
3 74153 Dual 4-line to 1-line data selectors/multiplexers
4
5
6 Pin layout and functions to access pins:
7
8 enable_w(0) [1] /1G VCC [16]
9 b_w [2] B /2G [15] enable_w(1)
10 input_line_w(0,3) [3] 1C3 A [14] a_w
11 input_line_w(0,2) [4] 1C2 2C3 [13] input_line_w(1,3)
12 input_line_w(0,1) [5] 1C1 2C2 [12] input_line_w(1,2)
13 input_line_w(0,0) [6] 1C0 2C1 [11] input_line_w(1,1)
14 output_r(0) [7] 1Y 2C0 [10] input_line_w(1,0)
15 [8] GND 2Y [9] output_r(1)
16
17
18 Truth table (all logic levels indicate the actual voltage on the line):
19
20 INPUTS | OUTPUT
21 |
22 G | B A | C0 C1 C2 C3 | Y
23 --+------+-------------+---
24 1 H | X X | X X X X | L
25 2 L | L L | X X X X | C0
26 3 L | L H | X X X X | C1
27 4 L | H L | X X X X | C2
28 5 L | H H | X X X X | C3
29 --+------+-------------+---
30 L = lo (0)
31 H = hi (1)
32 X = any state
33
34 *****************************************************************************/
35
36 #include "driver.h"
37 #include "machine/74153.h"
38
39
40 #define MAX_TTL74153 4
41
42 struct TTL74153
43 {
44 /* callback */
45 void (*output_cb)(void);
46
47 /* inputs */
48 int a; /* pin 14 */
49 int b; /* pin 2 */
50 int input_lines[2][4]; /* pins 3-6,10-13 */
51 int enable[2]; /* pins 1,9 */
52
53 /* output */
54 int output[2]; /* pins 7,9 */
55
56 /* internals */
57 int last_output[2];
58 };
59
60 static struct TTL74153 chips[MAX_TTL74153];
61
62
TTL74153_update(int which)63 void TTL74153_update(int which)
64 {
65 int sel;
66 int section;
67
68
69 sel = (chips[which].b << 1) | chips[which].a;
70
71
72 /* process both sections */
73 for (section = 0; section < 2; section++)
74 {
75 if (chips[which].enable[section])
76 chips[which].output[section] = 0; // row 1 in truth table
77 else
78 chips[which].output[section] = chips[which].input_lines[section][sel];
79 }
80
81
82 /* call callback if either of the outputs changed */
83 if ( chips[which].output_cb &&
84 ((chips[which].output[0] != chips[which].last_output[0]) ||
85 (chips[which].output[1] != chips[which].last_output[1])))
86 {
87 chips[which].last_output[0] = chips[which].output[0];
88 chips[which].last_output[1] = chips[which].output[1];
89
90 chips[which].output_cb();
91 }
92 }
93
94
TTL74153_a_w(int which,int data)95 void TTL74153_a_w(int which, int data)
96 {
97 chips[which].a = data ? 1 : 0;
98 }
99
100
TTL74153_b_w(int which,int data)101 void TTL74153_b_w(int which, int data)
102 {
103 chips[which].b = data ? 1 : 0;
104 }
105
106
TTL74153_input_line_w(int which,int section,int input_line,int data)107 void TTL74153_input_line_w(int which, int section, int input_line, int data)
108 {
109 chips[which].input_lines[section][input_line] = data ? 1 : 0;
110 }
111
112
TTL74153_enable_w(int which,int section,int data)113 void TTL74153_enable_w(int which, int section, int data)
114 {
115 chips[which].enable[section] = data ? 1 : 0;
116 }
117
118
TTL74153_output_r(int which,int section)119 int TTL74153_output_r(int which, int section)
120 {
121 return chips[which].output[section];
122 }
123
124
125
TTL74153_config(int which,const struct TTL74153_interface * intf)126 void TTL74153_config(int which, const struct TTL74153_interface *intf)
127 {
128 if (which >= MAX_TTL74153)
129 {
130 logerror("Only %d 74153's are supported at this time.\n", MAX_TTL74153);
131 return;
132 }
133
134
135 chips[which].output_cb = (intf ? intf->output_cb : 0);
136 chips[which].a = 1;
137 chips[which].b = 1;
138 chips[which].enable[0] = 1;
139 chips[which].enable[1] = 1;
140 chips[which].input_lines[0][0] = 1;
141 chips[which].input_lines[0][1] = 1;
142 chips[which].input_lines[0][2] = 1;
143 chips[which].input_lines[0][3] = 1;
144 chips[which].input_lines[1][0] = 1;
145 chips[which].input_lines[1][1] = 1;
146 chips[which].input_lines[1][2] = 1;
147 chips[which].input_lines[1][3] = 1;
148
149 chips[which].last_output[0] = -1;
150 chips[which].last_output[1] = -1;
151 }
152