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cf76e892 JPM |
1 | // |
2 | // Memory Track cartridge emulation | |
3 | // | |
4 | // by James Hammons | |
5 | // (C) 2016 Underground Software | |
6 | // | |
7 | // The Memory Track is just a large(-ish) EEPROM, holding 128K. We emulate the | |
8 | // Atmel part, since it seems to be easier to deal with than the AMD part. The | |
9 | // way it works is the 68K checks in its R/W functions to see if the MT is | |
10 | // inserted, and, if so, call the R/W functions here. It also checks to see if | |
11 | // the ROM width was changed to 32-bit; if not, then it reads the normal ROM in | |
12 | // the ROM space like usual. | |
13 | // | |
14 | // The Atmel part reads/writes a single byte into a long space. So we have to | |
15 | // adjust for that when reading from/writing to the NVRAM. | |
16 | // | |
17 | // JLH = James Hammons <jlhamm@acm.org> | |
18 | // JPM = Jean-Paul Mari <djipi.mari@gmail.com> | |
19 | // | |
20 | // Who When What | |
21 | // --- ---------- ----------------------------------------------------------- | |
22 | // JLH 06/12/2016 Created this file ;-) | |
23 | // JPM 06/06/2016 Visual Studio support | |
24 | // | |
25 | ||
26 | #include "memtrack.h" | |
27 | ||
28 | #include <stdlib.h> | |
29 | #include <string.h> | |
30 | #include "log.h" // JPM: changed <log.h> to "log.h" | |
31 | #include "settings.h" // JPM: changed <settings.h> to "settings.h" | |
32 | ||
33 | ||
34 | #define MEMTRACK_FILENAME "memtrack.eeprom" | |
35 | //#define DEBUG_MEMTRACK | |
36 | ||
37 | enum { MT_NONE, MT_PROD_ID, MT_RESET, MT_WRITE_ENABLE }; | |
38 | enum { MT_IDLE, MT_PHASE1, MT_PHASE2 }; | |
39 | ||
40 | uint8_t mtMem[0x20000]; | |
41 | uint8_t mtCommand = MT_NONE; | |
42 | uint8_t mtState = MT_IDLE; | |
43 | bool haveMT = false; | |
44 | char mtFilename[MAX_PATH]; | |
45 | ||
46 | // Private function prototypes | |
47 | void MTWriteFile(void); | |
48 | void MTStateMachine(uint8_t reg, uint16_t data); | |
49 | ||
50 | ||
51 | void MTInit(void) | |
52 | { | |
53 | sprintf(mtFilename, "%s%s", vjs.EEPROMPath, MEMTRACK_FILENAME); | |
54 | FILE * fp = fopen(mtFilename, "rb"); | |
55 | ||
56 | if (fp) | |
57 | { | |
58 | size_t ignored = fread(mtMem, 1, 0x20000, fp); | |
59 | fclose(fp); | |
60 | WriteLog("MT: Loaded NVRAM from %s\n", mtFilename); | |
61 | haveMT = true; | |
62 | } | |
63 | else | |
64 | WriteLog("MT: Could not open file \"%s\"!\n", mtFilename); | |
65 | } | |
66 | ||
67 | ||
68 | void MTReset(void) | |
69 | { | |
70 | if (!haveMT) | |
71 | memset(mtMem, 0xFF, 0x20000); | |
72 | } | |
73 | ||
74 | ||
75 | void MTDone(void) | |
76 | { | |
77 | MTWriteFile(); | |
78 | WriteLog("MT: Done.\n"); | |
79 | } | |
80 | ||
81 | ||
82 | void MTWriteFile(void) | |
83 | { | |
84 | if (!haveMT) | |
85 | return; | |
86 | ||
87 | FILE * fp = fopen(mtFilename, "wb"); | |
88 | ||
89 | if (fp) | |
90 | { | |
91 | fwrite(mtMem, 1, 0x20000, fp); | |
92 | fclose(fp); | |
93 | } | |
94 | else | |
95 | WriteLog("MT: Could not create file \"%s\"!", mtFilename); | |
96 | } | |
97 | ||
98 | ||
99 | // | |
100 | // This is crappy, there doesn't seem to be a word interface to the NVRAM. But | |
101 | // we'll keep this as a placeholder for now. | |
102 | // | |
103 | uint16_t MTReadWord(uint32_t addr) | |
104 | { | |
105 | uint32_t value = MTReadLong(addr); | |
106 | ||
107 | if ((addr & 0x03) == 0) | |
108 | value >>= 16; | |
109 | else if ((addr & 0x03) == 2) | |
110 | value &= 0xFFFF; | |
111 | ||
112 | #ifdef DEBUG_MEMTRACK | |
113 | WriteLog("MT: Reading word @ $%06X: $%04X\n", addr, value); | |
114 | #endif | |
115 | ||
116 | return (uint16_t)value; | |
117 | } | |
118 | ||
119 | ||
120 | uint32_t MTReadLong(uint32_t addr) | |
121 | { | |
122 | uint32_t value = 0; | |
123 | ||
124 | if (mtCommand == MT_PROD_ID) | |
125 | { | |
126 | if (addr == 0x800000) | |
127 | value = 0x1F; | |
128 | else if (addr == 0x800004) | |
129 | value = 0xD5; | |
130 | } | |
131 | else | |
132 | { | |
133 | value = (uint32_t)mtMem[(addr & 0x7FFFC) >> 2]; | |
134 | } | |
135 | ||
136 | // We do this because we're not sure how the real thing behaves; but it | |
137 | // seems reasonable on its face to do it this way. :-P So we turn off write | |
138 | // mode when reading the NVRAM. | |
139 | if (mtCommand == MT_WRITE_ENABLE) | |
140 | mtCommand = MT_NONE; | |
141 | ||
142 | #ifdef DEBUG_MEMTRACK | |
143 | WriteLog("MT: Reading long @ $%06X: $%08X\n", addr, value << 16); | |
144 | #endif | |
145 | return value << 16; | |
146 | } | |
147 | ||
148 | ||
149 | void MTWriteWord(uint32_t addr, uint16_t data) | |
150 | { | |
151 | // We don't care about writes to long offsets + 2 | |
152 | if ((addr & 0x3) == 2) | |
153 | return; | |
154 | ||
155 | #ifdef DEBUG_MEMTRACK | |
156 | WriteLog("MT: Writing word @ $%06X: $%04X (Writing is %sabled)\n", addr, data, (mtCommand == MT_WRITE_ENABLE ? "en" : "dis")); | |
157 | #endif | |
158 | ||
159 | // Write to the NVRAM if it's enabled... | |
160 | if (mtCommand == MT_WRITE_ENABLE) | |
161 | { | |
162 | mtMem[(addr & 0x7FFFC) >> 2] = (uint8_t)(data & 0xFF); | |
163 | return; | |
164 | } | |
165 | ||
166 | switch (addr) | |
167 | { | |
168 | case (0x800000 + (4 * 0x5555)): // $815554 | |
169 | MTStateMachine(0, data); | |
170 | break; | |
171 | case (0x800000 + (4 * 0x2AAA)): // $80AAA8 | |
172 | MTStateMachine(1, data); | |
173 | break; | |
174 | } | |
175 | } | |
176 | ||
177 | ||
178 | void MTWriteLong(uint32_t addr, uint32_t data) | |
179 | { | |
180 | // Strip off lower 3 bits of the passed in address | |
181 | addr &= 0xFFFFFC; | |
182 | ||
183 | MTWriteWord(addr + 0, data & 0xFFFF); | |
184 | MTWriteWord(addr + 2, data >> 16); | |
185 | } | |
186 | ||
187 | ||
188 | void MTStateMachine(uint8_t reg, uint16_t data) | |
189 | { | |
190 | #ifdef DEBUG_MEMTRACK | |
191 | WriteLog("MTStateMachine: reg = %u, data = $%02X, current state = %u\n", reg, data, mtState); | |
192 | #endif | |
193 | switch (mtState) | |
194 | { | |
195 | case MT_IDLE: | |
196 | if ((reg == 0) && (data == 0xAA)) | |
197 | mtState = MT_PHASE1; | |
198 | ||
199 | break; | |
200 | case MT_PHASE1: | |
201 | if ((reg == 1) && (data == 0x55)) | |
202 | mtState = MT_PHASE2; | |
203 | else | |
204 | mtState = MT_IDLE; | |
205 | ||
206 | break; | |
207 | case MT_PHASE2: | |
208 | if (reg == 0) | |
209 | { | |
210 | if (data == 0x90) // Product ID | |
211 | mtCommand = MT_PROD_ID; | |
212 | else if (data == 0xF0) // Reset | |
213 | mtCommand = MT_NONE; | |
214 | else if (data == 0xA0) // Write enagle | |
215 | mtCommand = MT_WRITE_ENABLE; | |
216 | else | |
217 | mtCommand = MT_NONE; | |
218 | } | |
219 | ||
220 | mtState = MT_IDLE; | |
221 | break; | |
222 | } | |
223 | #ifdef DEBUG_MEMTRACK | |
224 | WriteLog(" state = %u, cmd = %u\n", mtState, mtCommand); | |
225 | #endif | |
226 | } | |
227 |