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diff --git a/src/emu/machine/74153.h b/src/emu/machine/74153.h
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+/*****************************************************************************
+
+ 74153 Dual 4-line to 1-line data selectors/multiplexers
+
+
+ Pin layout and functions to access pins:
+
+ enable_w(0) [1] /1G VCC [16]
+ b_w [2] B /2G [15] enable_w(1)
+ input_line_w(0,3) [3] 1C3 A [14] a_w
+ input_line_w(0,2) [4] 1C2 2C3 [13] input_line_w(1,3)
+ input_line_w(0,1) [5] 1C1 2C2 [12] input_line_w(1,2)
+ input_line_w(0,0) [6] 1C0 2C1 [11] input_line_w(1,1)
+ output_r(0) [7] 1Y 2C0 [10] input_line_w(1,0)
+ [8] GND 2Y [9] output_r(1)
+
+
+ Truth table (all logic levels indicate the actual voltage on the line):
+
+ INPUTS | OUTPUT
+ |
+ G | B A | C0 C1 C2 C3 | Y
+ --+------+-------------+---
+ H | X X | X X X X | L
+ L | L L | X X X X | C0
+ L | L H | X X X X | C1
+ L | H L | X X X X | C2
+ L | H H | X X X X | C3
+ --+------+-------------+---
+ L = lo (0)
+ H = hi (1)
+ X = any state
+
+*****************************************************************************/
+
+#ifndef TTL74153_H
+#define TTL74153_H
+
+
+/* The interface structure */
+struct TTL74153_interface
+{
+ void (*output_cb)(void);
+};
+
+
+void TTL74153_config(int which, const struct TTL74153_interface *intf);
+
+/* must call TTL74153_update() after setting the inputs */
+void TTL74153_update(int which);
+
+void TTL74153_a_w(int which, int data);
+void TTL74153_b_w(int which, int data);
+void TTL74153_input_line_w(int which, int section, int input_line, int data);
+void TTL74153_enable_w(int which, int section, int data);
+int TTL74153_output_r(int which, int section);
+
+#endif