emulator/ppu.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <time.h>
   4 #include <string.h>
   5
   6 #include "clock.h"
   7 #include "tools.h"
   8 #include "vga.h"
   9 #include "ppucore.h"
  10
  11 void set_vga_base(unsigned char* base);
  12 void *vga_shm_get(void);
  13 void vga_shm_free(void* addr);
  14 void release_bus(void);
  15
  16 struct ppu_cpu_pin {
  17     unsigned int ce     :1;     /*chip enable*/
  18     unsigned int rw     :1;     /*assert on write.*/
  19     unsigned int vblank :1;     /*connected to nmi*/
  20 };
  21
  22 struct ppu_cart_pin {
  23     unsigned int rd     :1;     /*read*/
  24     unsigned int wr     :1;     /*write.*/
  25 };
  26
  27 static struct ppu_cpu_pin  ppu_pin;
  28 static struct ppu_cart_pin cart_pin;
  29
  30 static unsigned short ppu_addr;
  31 static unsigned char ppu_data;
  32
  33 static unsigned char* vga_shared_buf;
  34
  35
  36 /*
  37  * ppucore r/w func ptr.
  38  * */
  39 typedef void (ppu_write_t)(unsigned char);
  40 typedef unsigned char (ppu_read_t)(void);
  41
  42 static void null_write(unsigned char);
  43 static unsigned char null_read(void);
  44
  45 static ppu_write_t *ppucore_write_func[8] = {
  46     ppu_ctrl1_set,
  47     ppu_ctrl2_set,
  48     null_write,
  49     sprite_data_set,
  50     sprite_addr_set,
  51     ppu_scroll_set,
  52     ppu_vram_addr_set,
  53     ppu_vram_data_set
  54 };
  55
  56 static ppu_read_t *ppucore_read_func[8] = {
  57     null_read,
  58     null_read,
  59     ppu_status_get,
  60     null_read,
  61     null_read,
  62     null_read,
  63     null_read,
  64     ppu_vram_data_get
  65 };
  66
  67 /*
  68 * JAPAN/US uses NTSC standard.
  69 *
  70 * NTSC:
  71 * ---------------------------------------------------------
  72 * Frames per second                            60
  73 * Time per frame (milliseconds)                16.67
  74 * Scanlines per frame (of which is V-Blank)    262 (20)
  75 * CPU cycles per scanline                      113.33
  76 * Resolution                                   256 x 224
  77 * CPU speed                                    1.79 MHz
  78 *
  79 * PPU clock                                    21.48 Mhz
  80 * */
  81
  82 void set_ppu_addr(unsigned short addr) {
  83     ppu_addr = addr;
  84 }
  85
  86 unsigned char get_ppu_data(void) {
  87     return ppu_data;
  88 }
  89
  90 void set_ppu_data(unsigned char data) {
  91     ppu_data = data;
  92 }
  93
  94 /*
  95  * write: rw = 1
  96  * read: rw = 0
  97  * */
  98 void set_ppu_rw_pin(int rw) {
  99     ppu_pin.rw = rw;
 100 }
 101
 102 void set_ppu_ce_pin(int ce) {
 103     ppu_pin.ce = ce;
 104     //let ram i/o on the bus.
 105     if (ce) {
 106         if (ppu_pin.rw) {
 107             //write cycle
 108             ppucore_write_func[ppu_addr](ppu_data);
 109         }
 110         else {
 111             //read cycle
 112             ppu_data = ppucore_read_func[ppu_addr]();
 113         }
 114         release_bus();
 115     }
 116 }
 117
 118 /*dummy I/O func*/
 119 static void null_write(unsigned char d){}
 120 static unsigned char null_read(void){return 0;}
 121
 122 int init_ppu(void) {
 123     int ret;
 124
 125     ppu_pin.ce = 0;
 126     ppu_pin.rw = 0;
 127     cart_pin.rd = 0;
 128     cart_pin.wr = 0;
 129
 130     ppu_addr = 0;
 131     ppu_data = 0;
 132
 133     /* get vga shared memory */
 134     if((vga_shared_buf = (unsigned char*)vga_shm_get()) == NULL)
 135     {
 136         fprintf(stderr, "error attaching shared memory.\n");
 137         return FALSE;
 138     }
 139
 140     memset(vga_shared_buf, 0, VGA_SHM_SIZE);
 141     set_vga_base((unsigned char*)vga_shared_buf);
 142
 143     ret = ppucore_init();
 144     if (ret == FALSE) {
 145         return FALSE;
 146     }
 147
 148     return TRUE;
 149 }
 150
 151 void clean_ppu(void) {
 152     clean_ppucore();
 153     vga_shm_free(vga_shared_buf);
 154 }
 155
 156