66 lines
1.5 KiB
C
66 lines
1.5 KiB
C
#include <stdio.h>
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#include <unistd.h>
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#include <sys/poll.h>
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#include <stdlib.h>
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#include "6502.h"
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#include "6850.h"
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static int n;
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static union UartStatusReg uart_SR;
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static uint8_t incoming_char;
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static int interactive;
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void init_uart(int is_interactive) {
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memory[DATA_ADDR] = 0;
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uart_SR.byte = 0;
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uart_SR.bits.TDRE = 1; // we are always ready to output data
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uart_SR.bits.RDRF = 0;
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incoming_char = 0;
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interactive = is_interactive;
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}
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int stdin_ready() {
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struct pollfd fds;
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fds.fd = 0; // stdin
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fds.events = POLLIN;
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return poll(&fds, 1, 0) == 1; // timeout = 0
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}
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void step_uart() {
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if (write_addr == &memory[DATA_ADDR]) {
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putchar(memory[DATA_ADDR]);
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if (memory[DATA_ADDR] == '\b') printf(" \b");
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fflush(stdout);
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write_addr = NULL;
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} else if (read_addr == &memory[DATA_ADDR]) {
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uart_SR.bits.RDRF = 0;
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read_addr = NULL;
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}
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/* update input register if empty */
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if ((n++ % 100) == 0) { // polling stdin every cycle is performance intensive. This is a bit of a dirty hack.
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if (!uart_SR.bits.RDRF && stdin_ready()) { // the real hardware has no buffer. Remote the RDRF check for more accurate emulation.
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if (read(0, &incoming_char, 1) != 1) {
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printf("Warning: read() returned 0\n");
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}
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if (interactive) {
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if (incoming_char == 0x18) { // CTRL+X
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printf("\r\n");
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exit(0);
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}
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if (incoming_char == 0x7F) { // Backspace
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incoming_char = '\b';
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}
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}
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uart_SR.bits.RDRF = 1;
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}
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}
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memory[DATA_ADDR] = incoming_char;
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memory[CTRL_ADDR] = uart_SR.byte;
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}
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