/***************************************************************************** 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 "emu.h" #include "machine/74148.h" typedef struct _ttl74148_state ttl74148_state; struct _ttl74148_state { /* callback */ void (*output_cb)(device_t *device); /* 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; }; INLINE ttl74148_state *get_safe_token(device_t *device) { assert(device != NULL); assert(device->type() == TTL74148); return (ttl74148_state *)downcast(device)->token(); } void ttl74148_update(device_t *device) { ttl74148_state *state = get_safe_token(device); if (state->enable_input) { // row 1 in truth table state->output = 0x07; state->output_valid = 1; state->enable_output = 1; } else { int bit0, bit1, bit2; /* this comes straight off the data sheet schematics */ bit0 = !(((!state->input_lines[1]) & state->input_lines[2] & state->input_lines[4] & state->input_lines[6]) | ((!state->input_lines[3]) & state->input_lines[4] & state->input_lines[6]) | ((!state->input_lines[5]) & state->input_lines[6]) | (!state->input_lines[7])); bit1 = !(((!state->input_lines[2]) & state->input_lines[4] & state->input_lines[5]) | ((!state->input_lines[3]) & state->input_lines[4] & state->input_lines[5]) | (!state->input_lines[6]) | (!state->input_lines[7])); bit2 = !((!state->input_lines[4]) | (!state->input_lines[5]) | (!state->input_lines[6]) | (!state->input_lines[7])); state->output = (bit2 << 2) | (bit1 << 1) | bit0; state->output_valid = (state->input_lines[0] & state->input_lines[1] & state->input_lines[2] & state->input_lines[3] & state->input_lines[4] & state->input_lines[5] & state->input_lines[6] & state->input_lines[7]); state->enable_output = !state->output_valid; } /* call callback if any of the outputs changed */ if ( state->output_cb && ((state->output != state->last_output) || (state->output_valid != state->last_output_valid) || (state->enable_output != state->last_enable_output))) { state->last_output = state->output; state->last_output_valid = state->output_valid; state->last_enable_output = state->enable_output; state->output_cb(device); } } void ttl74148_input_line_w(device_t *device, int input_line, int data) { ttl74148_state *state = get_safe_token(device); state->input_lines[input_line] = data ? 1 : 0; } void ttl74148_enable_input_w(device_t *device, int data) { ttl74148_state *state = get_safe_token(device); state->enable_input = data ? 1 : 0; } int ttl74148_output_r(device_t *device) { ttl74148_state *state = get_safe_token(device); return state->output; } int ttl74148_output_valid_r(device_t *device) { ttl74148_state *state = get_safe_token(device); return state->output_valid; } int ttl74148_enable_output_r(device_t *device) { ttl74148_state *state = get_safe_token(device); return state->enable_output; } static DEVICE_START( ttl74148 ) { ttl74148_config *config = (ttl74148_config *)downcast(device->baseconfig()).inline_config(); ttl74148_state *state = get_safe_token(device); state->output_cb = config->output_cb; device->save_item(NAME(state->input_lines)); device->save_item(NAME(state->enable_input)); device->save_item(NAME(state->output)); device->save_item(NAME(state->output_valid)); device->save_item(NAME(state->enable_output)); device->save_item(NAME(state->last_output)); device->save_item(NAME(state->last_output_valid)); device->save_item(NAME(state->last_enable_output)); } static DEVICE_RESET( ttl74148 ) { ttl74148_state *state = get_safe_token(device); state->enable_input = 1; state->input_lines[0] = 1; state->input_lines[1] = 1; state->input_lines[2] = 1; state->input_lines[3] = 1; state->input_lines[4] = 1; state->input_lines[5] = 1; state->input_lines[6] = 1; state->input_lines[7] = 1; state->last_output = -1; state->last_output_valid = -1; state->last_enable_output = -1; } static const char DEVTEMPLATE_SOURCE[] = __FILE__; #define DEVTEMPLATE_ID(p,s) p##ttl74148##s #define DEVTEMPLATE_FEATURES DT_HAS_START | DT_HAS_RESET | DT_HAS_INLINE_CONFIG #define DEVTEMPLATE_NAME "74148" #define DEVTEMPLATE_FAMILY "TTL" #include "devtempl.h" DEFINE_LEGACY_DEVICE(TTL74148, ttl74148);