Fri, 03 Dec 2010 00:20:36 +0000
fix missing shift-right in video output code
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <stdint.h>
4 #include <stdbool.h>
5 #include <malloc.h>
6 #include <string.h>
8 #include "SDL.h"
10 #include "musashi/m68k.h"
11 #include "version.h"
12 #include "state.h"
13 #include "memory.h"
15 void FAIL(char *err)
16 {
17 state_done();
18 fprintf(stderr, "ERROR: %s\nExiting...\n", err);
19 exit(EXIT_FAILURE);
20 }
22 /**
23 * @brief Set the pixel at (x, y) to the given value
24 * @note The surface must be locked before calling this!
25 * @param surface SDL surface upon which to draw
26 * @param x X co-ordinate
27 * @param y Y co-ordinate
28 * @param pixel Pixel value (from SDL_MapRGB)
29 */
30 void putpixel(SDL_Surface *surface, int x, int y, Uint32 pixel)
31 {
32 int bpp = surface->format->BytesPerPixel;
33 /* Here p is the address to the pixel we want to set */
34 Uint8 *p = (Uint8 *)surface->pixels + y * surface->pitch + x * bpp;
36 switch (bpp) {
37 case 1:
38 *p = pixel;
39 break;
41 case 2:
42 *(Uint16 *)p = pixel;
43 break;
45 case 3:
46 if (SDL_BYTEORDER == SDL_BIG_ENDIAN) {
47 p[0] = (pixel >> 16) & 0xff;
48 p[1] = (pixel >> 8) & 0xff;
49 p[2] = pixel & 0xff;
50 }
51 else {
52 p[0] = pixel & 0xff;
53 p[1] = (pixel >> 8) & 0xff;
54 p[2] = (pixel >> 16) & 0xff;
55 }
56 break;
58 case 4:
59 *(Uint32 *)p = pixel;
60 break;
62 default:
63 break; /* shouldn't happen, but avoids warnings */
64 } // switch
65 }
68 /**
69 * @brief Refresh the screen.
70 * @param surface SDL surface upon which to draw.
71 */
72 void refreshScreen(SDL_Surface *s)
73 {
74 // Lock the screen surface (if necessary)
75 if (SDL_MUSTLOCK(s)) {
76 if (SDL_LockSurface(s) < 0) {
77 fprintf(stderr, "ERROR: Unable to lock screen!\n");
78 exit(EXIT_FAILURE);
79 }
80 }
82 // Map the foreground and background colours
83 Uint32 fg = SDL_MapRGB(s->format, 0x00, 0xFF, 0x00); // green foreground
84 // Uint32 fg = SDL_MapRGB(s->format, 0xFF, 0xC1, 0x06); // amber foreground
85 // Uint32 fg = SDL_MapRGB(s->format, 0xFF, 0xFF, 0xFF); // white foreground
86 Uint32 bg = SDL_MapRGB(s->format, 0x00, 0x00, 0x00); // black background
88 // Refresh the 3B1 screen area first. TODO: only do this if VRAM has actually changed!
89 uint32_t vram_address = 0;
90 for (int y=0; y<348; y++) {
91 for (int x=0; x<720; x+=16) { // 720 pixels, monochrome, packed into 16bit words
92 // Get the pixel
93 uint16_t val = RD16(state.vram, vram_address, sizeof(state.vram)-1);
94 vram_address += 2;
95 // Now copy it to the video buffer
96 for (int px=0; px<16; px++) {
97 if (val & 1)
98 putpixel(s, x+px, y, fg);
99 else
100 putpixel(s, x+px, y, bg);
101 val >>= 1;
102 }
103 }
104 }
106 // TODO: blit LEDs and status info
108 // Unlock the screen surface
109 if (SDL_MUSTLOCK(s)) {
110 SDL_UnlockSurface(s);
111 }
113 // Trigger a refresh -- TODO: partial refresh depending on whether we
114 // refreshed the screen area, status area, both, or none. Use SDL_UpdateRect() for this.
115 SDL_Flip(s);
116 }
118 /****************************
119 * blessed be thy main()...
120 ****************************/
122 int main(void)
123 {
124 // copyright banner
125 printf("FreeBee: A Quick-and-Dirty AT&T 3B1 Emulator. Version %s, %s mode.\n", VER_FULLSTR, VER_BUILD_TYPE);
126 printf("Copyright (C) 2010 P. A. Pemberton. All rights reserved.\nLicensed under the Apache License Version 2.0.\n");
127 printf("Musashi M680x0 emulator engine developed by Karl Stenerud <kstenerud@gmail.com>\n");
128 printf("Built %s by %s@%s.\n", VER_COMPILE_DATETIME, VER_COMPILE_BY, VER_COMPILE_HOST);
129 printf("Compiler: %s\n", VER_COMPILER);
130 printf("CFLAGS: %s\n", VER_CFLAGS);
131 printf("\n");
133 // set up system state
134 // 512K of RAM
135 state_init(512*1024);
137 // set up musashi and reset the CPU
138 m68k_set_cpu_type(M68K_CPU_TYPE_68010);
139 m68k_pulse_reset();
141 // Set up SDL
142 if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER) == -1) {
143 printf("Could not initialise SDL: %s.\n", SDL_GetError());
144 exit(EXIT_FAILURE);
145 }
147 // Make sure SDL cleans up after itself
148 atexit(SDL_Quit);
150 // Set up the video display
151 SDL_Surface *screen = NULL;
152 if ((screen = SDL_SetVideoMode(720, 384, 8, SDL_SWSURFACE | SDL_ANYFORMAT)) == NULL) {
153 printf("Could not find a suitable video mode: %s.\n", SDL_GetError());
154 exit(EXIT_FAILURE);
155 }
156 printf("Set %dx%d at %d bits-per-pixel mode\n\n", screen->w, screen->h, screen->format->BitsPerPixel);
157 SDL_WM_SetCaption("FreeBee 3B1 emulator", "FreeBee");
159 /***
160 * The 3B1 CPU runs at 10MHz, with DMA running at 1MHz and video refreshing at
161 * around 60Hz (???), with a 60Hz periodic interrupt.
162 */
163 const uint32_t TIMESLOT_FREQUENCY = 240; // Hz
164 const uint32_t MILLISECS_PER_TIMESLOT = 1e3 / TIMESLOT_FREQUENCY;
165 const uint32_t CLOCKS_PER_60HZ = (10e6 / 60);
166 uint32_t next_timeslot = SDL_GetTicks() + MILLISECS_PER_TIMESLOT;
167 uint32_t clock_cycles = 0;
168 bool exitEmu = false;
169 for (;;) {
170 // Run the CPU for however many cycles we need to. CPU core clock is
171 // 10MHz, and we're running at 240Hz/timeslot. Thus: 10e6/240 or
172 // 41667 cycles per timeslot.
173 clock_cycles += m68k_execute(10e6/TIMESLOT_FREQUENCY);
175 // TODO: run DMA here
177 // Is it time to run the 60Hz periodic interrupt yet?
178 if (clock_cycles > CLOCKS_PER_60HZ) {
179 // Refresh the screen
180 refreshScreen(screen);
181 // TODO: trigger periodic interrupt (if enabled)
182 // decrement clock cycle counter, we've handled the intr.
183 clock_cycles -= CLOCKS_PER_60HZ;
184 }
186 // make sure frame rate is equal to real time
187 uint32_t now = SDL_GetTicks();
188 if (now < next_timeslot) {
189 // timeslot finished early -- eat up some time
190 SDL_Delay(next_timeslot - now);
191 } else {
192 // timeslot finished late -- skip ahead to gain time
193 // TODO: if this happens a lot, we should let the user know
194 // that their PC might not be fast enough...
195 next_timeslot = now;
196 }
197 // advance to the next timeslot
198 next_timeslot += MILLISECS_PER_TIMESLOT;
200 // if we've been asked to exit the emulator, then do so.
201 if (exitEmu) break;
202 }
204 // shut down and exit
205 SDL_Quit();
207 return 0;
208 }