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Diffstat (limited to 'src/emu/machine/74153.c')
-rw-r--r-- | src/emu/machine/74153.c | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/src/emu/machine/74153.c b/src/emu/machine/74153.c new file mode 100644 index 00000000000..b8f1109d830 --- /dev/null +++ b/src/emu/machine/74153.c @@ -0,0 +1,151 @@ +/***************************************************************************** + + 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 + --+------+-------------+--- +1 H | X X | X X X X | L +2 L | L L | X X X X | C0 +3 L | L H | X X X X | C1 +4 L | H L | X X X X | C2 +5 L | H H | X X X X | C3 + --+------+-------------+--- + L = lo (0) + H = hi (1) + X = any state + +*****************************************************************************/ + +#include "driver.h" +#include "machine/74153.h" + + +#define MAX_TTL74153 9 + +struct TTL74153 +{ + /* callback */ + void (*output_cb)(void); + + /* inputs */ + int a; /* pin 14 */ + int b; /* pin 2 */ + int input_lines[2][4]; /* pins 3-6,10-13 */ + int enable[2]; /* pins 1,15 */ + + /* output */ + int output[2]; /* pins 7,9 */ + + /* internals */ + int last_output[2]; +}; + +static struct TTL74153 chips[MAX_TTL74153]; + + +void TTL74153_update(int which) +{ + int sel; + int section; + + + sel = (chips[which].b << 1) | chips[which].a; + + + /* process both sections */ + for (section = 0; section < 2; section++) + { + if (chips[which].enable[section]) + chips[which].output[section] = 0; // row 1 in truth table + else + chips[which].output[section] = chips[which].input_lines[section][sel]; + } + + + /* call callback if either of the outputs changed */ + if ( chips[which].output_cb && + ((chips[which].output[0] != chips[which].last_output[0]) || + (chips[which].output[1] != chips[which].last_output[1]))) + { + chips[which].last_output[0] = chips[which].output[0]; + chips[which].last_output[1] = chips[which].output[1]; + + chips[which].output_cb(); + } +} + + +void TTL74153_a_w(int which, int data) +{ + chips[which].a = data ? 1 : 0; +} + + +void TTL74153_b_w(int which, int data) +{ + chips[which].b = data ? 1 : 0; +} + + +void TTL74153_input_line_w(int which, int section, int input_line, int data) +{ + chips[which].input_lines[section][input_line] = data ? 1 : 0; +} + + +void TTL74153_enable_w(int which, int section, int data) +{ + chips[which].enable[section] = data ? 1 : 0; +} + + +int TTL74153_output_r(int which, int section) +{ + return chips[which].output[section]; +} + + + +void TTL74153_config(int which, const struct TTL74153_interface *intf) +{ + if (which >= MAX_TTL74153) + { + logerror("Only %d 74153's are supported at this time.\n", MAX_TTL74153); + return; + } + + + chips[which].output_cb = (intf ? intf->output_cb : 0); + chips[which].a = 1; + chips[which].b = 1; + chips[which].enable[0] = 1; + chips[which].enable[1] = 1; + chips[which].input_lines[0][0] = 1; + chips[which].input_lines[0][1] = 1; + chips[which].input_lines[0][2] = 1; + chips[which].input_lines[0][3] = 1; + chips[which].input_lines[1][0] = 1; + chips[which].input_lines[1][1] = 1; + chips[which].input_lines[1][2] = 1; + chips[which].input_lines[1][3] = 1; + + chips[which].last_output[0] = -1; + chips[which].last_output[1] = -1; +} |