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Support for the Realtec mapper. Needs testing with games besides The Earth Defend
author Michael Pavone <pavone@retrodev.com>
date Thu, 02 Mar 2017 21:08:33 -0800
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children f13f51e9f9f2
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1258:1148567ab355 1259:23c94f5266d1
1 #include <stdint.h>
2 #include <stdlib.h>
3 #include <string.h>
4 #include "romdb.h"
5 #include "genesis.h"
6 #include "util.h"
7
8 typedef struct {
9 uint8_t rom_space[512*1024];
10 uint8_t regs[3];
11 } realtec;
12
13
14 uint8_t realtec_detect(uint8_t *rom, uint32_t rom_size)
15 {
16 //All Realtec mapper games are 512KB total
17 if (rom_size != 512*1024) {
18 return 0;
19 }
20 return memcmp(rom + 0x7E100, "SEGA", 4) == 0;
21 }
22
23 static void *realtec_write_b(uint32_t address, void *context, uint8_t value)
24 {
25 if (address & 1) {
26 return context;
27 }
28 m68k_context *m68k = context;
29 genesis_context *gen = m68k->system;
30 if (!gen->extra) {
31 gen->extra = m68k->mem_pointers[0];
32 }
33 realtec *r = gen->extra;
34 uint32_t offset = address >> 13;
35 uint8_t dirty = 0;
36 if (offset < 3 && r->regs[offset] != value) {
37 r->regs[offset] = value;
38 //other regs are only 3 bits, so assume 3 for this one too
39 uint32_t size = (r->regs[1] & 0x7) << 17;
40 uint32_t start = (r->regs[2] & 7) << 17 | (r->regs[0] & 6) << 19;
41 if (size > 512*1024) {
42 size = 512*1024;
43 }
44 for(uint32_t cur = 0; cur < 512*1024; cur += size)
45 {
46 if (start + size > 512*1024) {
47 memcpy(r->rom_space + cur, gen->cart + start/2, 512*1024-start);
48 //assume it wraps
49 memcpy(r->rom_space + cur + 512*1024-start, gen->cart, size - (512*1024-start));
50 } else {
51 memcpy(r->rom_space + cur, gen->cart + start/2, size);
52 }
53 }
54 m68k_invalidate_code_range(gen->m68k, 0, 0x400000);
55 }
56 return context;
57 }
58
59 static void *realtec_write_w(uint32_t address, void *context, uint16_t value)
60 {
61 return realtec_write_b(address, context, value >> 8);
62 }
63
64 rom_info realtec_configure_rom(uint8_t *rom, uint32_t rom_size, memmap_chunk const *base_map, uint32_t base_chunks)
65 {
66 rom_info info;
67 realtec *r = calloc(sizeof(realtec), 1);
68 for (uint32_t i = 0; i < 512*1024; i += 8*1024)
69 {
70 memcpy(r->rom_space + i, rom + 0x7E000, 8*1024);
71 }
72 byteswap_rom(512*1024, (uint16_t *)r->rom_space);
73
74 uint8_t *name_start = NULL, *name_end = NULL;
75 for (int i = 0x90; i < 0xE0; i++)
76 {
77 if (name_start) {
78 if (rom[i] < ' ' || rom[i] > 0x80 || !memcmp(rom+i, "ARE", 3)) {
79 name_end = rom+i;
80 break;
81 }
82 } else if (rom[i] > ' ' && rom[i] < 0x80) {
83 name_start = rom + i;
84 }
85 }
86 if (name_start && !name_end) {
87 name_end = rom + 0xE0;
88 }
89 if (name_end) {
90 while (name_end > name_start && name_end[-1] == ' ')
91 {
92 name_end--;
93 }
94 info.name = malloc(name_end-name_start+1);
95 memcpy(info.name, name_start, name_end-name_start);
96 info.name[name_end-name_start] = 0;
97 } else {
98 info.name = strdup("Realtec Game");
99 }
100 info.save_type = SAVE_NONE;
101 info.save_size = 0;
102 info.save_buffer = NULL;
103 info.num_eeprom = 0;
104 info.eeprom_map = NULL;
105 info.port1_override = info.port2_override = info.ext_override = info.mouse_mode = NULL;
106 info.map_chunks = base_chunks + 2;
107 info.map = calloc(sizeof(memmap_chunk), info.map_chunks);
108 info.map[0].mask = sizeof(r->rom_space)-1;
109 info.map[0].flags = MMAP_READ|MMAP_CODE|MMAP_PTR_IDX;
110 info.map[0].start = 0;
111 info.map[0].end = 0x400000;
112 info.map[0].buffer = r->rom_space;
113 info.map[0].write_16 = NULL;
114 info.map[0].read_16 = NULL;
115 info.map[0].write_8 = NULL;
116 info.map[0].read_8 = NULL;
117 info.map[1].mask = 0x7FFF;
118 info.map[1].flags = 0;
119 info.map[1].start = 0x400000;
120 info.map[1].end = 0x800000;
121 info.map[1].write_16 = realtec_write_w;
122 info.map[1].write_8 = realtec_write_b;
123 info.map[1].read_16 = NULL;
124 info.map[1].read_8 = NULL;
125 memcpy(info.map + 2, base_map, base_chunks * sizeof(memmap_chunk));
126
127 return info;
128 }