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-rw-r--r--src/emu/machine/74148.c193
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diff --git a/src/emu/machine/74148.c b/src/emu/machine/74148.c
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+++ b/src/emu/machine/74148.c
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+/*****************************************************************************
+
+ 74148 8-line-to-3-line priority encoder
+
+
+ Pin layout and functions to access pins:
+
+ input_line_w(4) [1] /IN4 VCC [16]
+ input_line_w(5) [2] /IN5 /EO [15] enable_output_r
+ input_line_w(6) [3] /IN6 /GS [14] output_valid_r
+ input_line_w(7) [4] /IN7 /IN3 [13] input_line_w(3)
+ enable_input_w [5] /EI /IN2 [12] input_line_w(2)
+ output_r [6] /A2 /IN1 [11] input_line_w(1)
+ output_r [7] /A1 /IN0 [10] input_line_w(0)
+ [8] GND /A0 [9] output_r
+
+
+ Truth table (all logic levels indicate the actual voltage on the line):
+
+ INPUTS | OUTPUTS
+ |
+ EI I0 I1 I2 I3 I4 I5 I6 I7 | A2 A1 A0 | GS EO
+ ----------------------------+----------+------
+ 1 H X X X X X X X X | H H H | H H
+ 2 L H H H H H H H H | H H H | H L
+ 3 L X X X X X X X L | L L L | L H
+ 4 L X X X X X X L H | L L H | L H
+ 5 L X X X X X L H H | L H L | L H
+ 6 L X X X X L H H H | L H H | L H
+ 7 L X X X L H H H H | H L L | L H
+ 8 L X X L H H H H H | H L H | L H
+ 9 L X L H H H H H H | H H L | L H
+ 10 L L H H H H H H H | H H H | L H
+ ----------------------------+----------+------
+ L = lo (0)
+ H = hi (1)
+ X = any state
+
+*****************************************************************************/
+
+#include "driver.h"
+#include "machine/74148.h"
+
+
+#define MAX_TTL74148 4
+
+struct TTL74148
+{
+ /* callback */
+ void (*output_cb)(void);
+
+ /* inputs */
+ int input_lines[8]; /* pins 1-4,10-13 */
+ int enable_input; /* pin 5 */
+
+ /* outputs */
+ int output; /* pins 6,7,9 */
+ int output_valid; /* pin 14 */
+ int enable_output; /* pin 15 */
+
+ /* internals */
+ int last_output;
+ int last_output_valid;
+ int last_enable_output;
+};
+
+static struct TTL74148 chips[MAX_TTL74148];
+
+
+void TTL74148_update(int which)
+{
+ if (chips[which].enable_input)
+ {
+ // row 1 in truth table
+ chips[which].output = 0x07;
+ chips[which].output_valid = 1;
+ chips[which].enable_output = 1;
+ }
+ else
+ {
+ int bit0, bit1, bit2;
+
+ /* this comes straight off the data sheet schematics */
+ bit0 = !((!chips[which].input_lines[1] &
+ chips[which].input_lines[2] &
+ chips[which].input_lines[4] &
+ chips[which].input_lines[6]) |
+ (!chips[which].input_lines[3] &
+ chips[which].input_lines[4] &
+ chips[which].input_lines[6]) |
+ (!chips[which].input_lines[5] &
+ chips[which].input_lines[6]) |
+ (!chips[which].input_lines[7]));
+
+ bit1 = !((!chips[which].input_lines[2] &
+ chips[which].input_lines[4] &
+ chips[which].input_lines[5]) |
+ (!chips[which].input_lines[3] &
+ chips[which].input_lines[4] &
+ chips[which].input_lines[5]) |
+ (!chips[which].input_lines[6]) |
+ (!chips[which].input_lines[7]));
+
+ bit2 = !((!chips[which].input_lines[4]) |
+ (!chips[which].input_lines[5]) |
+ (!chips[which].input_lines[6]) |
+ (!chips[which].input_lines[7]));
+
+ chips[which].output = (bit2 << 2) | (bit1 << 1) | bit0;
+
+ chips[which].output_valid = (chips[which].input_lines[0] &
+ chips[which].input_lines[1] &
+ chips[which].input_lines[2] &
+ chips[which].input_lines[3] &
+ chips[which].input_lines[4] &
+ chips[which].input_lines[5] &
+ chips[which].input_lines[6] &
+ chips[which].input_lines[7]);
+
+ chips[which].enable_output = !chips[which].output_valid;
+ }
+
+
+ /* call callback if any of the outputs changed */
+ if ( chips[which].output_cb &&
+ ((chips[which].output != chips[which].last_output) ||
+ (chips[which].output_valid != chips[which].last_output_valid) ||
+ (chips[which].enable_output != chips[which].last_enable_output)))
+ {
+ chips[which].last_output = chips[which].output;
+ chips[which].last_output_valid = chips[which].output_valid;
+ chips[which].last_enable_output = chips[which].enable_output;
+
+ chips[which].output_cb();
+ }
+}
+
+
+void TTL74148_input_line_w(int which, int input_line, int data)
+{
+ chips[which].input_lines[input_line] = data ? 1 : 0;
+}
+
+
+void TTL74148_enable_input_w(int which, int data)
+{
+ chips[which].enable_input = data ? 1 : 0;
+}
+
+
+int TTL74148_output_r(int which)
+{
+ return chips[which].output;
+}
+
+
+int TTL74148_output_valid_r(int which)
+{
+ return chips[which].output_valid;
+}
+
+
+int TTL74148_enable_output_r(int which)
+{
+ return chips[which].enable_output;
+}
+
+
+
+void TTL74148_config(int which, const struct TTL74148_interface *intf)
+{
+ if (which >= MAX_TTL74148)
+ {
+ logerror("Only %d 74148's are supported at this time.\n", MAX_TTL74148);
+ return;
+ }
+
+
+ chips[which].output_cb = (intf ? intf->output_cb : 0);
+ chips[which].enable_input = 1;
+ chips[which].input_lines[0] = 1;
+ chips[which].input_lines[1] = 1;
+ chips[which].input_lines[2] = 1;
+ chips[which].input_lines[3] = 1;
+ chips[which].input_lines[4] = 1;
+ chips[which].input_lines[5] = 1;
+ chips[which].input_lines[6] = 1;
+ chips[which].input_lines[7] = 1;
+
+ chips[which].last_output = -1;
+ chips[which].last_output_valid = -1;
+ chips[which].last_enable_output = -1;
+}