summaryrefslogtreecommitdiff
path: root/hw/eeprom93xx.c
blob: 14f01891434976d47286276b15483e7b3ca30472 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
/*
 * QEMU EEPROM 93xx emulation
 *
 * Copyright (c) 2006-2007 Stefan Weil
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

/* Emulation for serial EEPROMs:
 * NMC93C06 256-Bit (16 x 16)
 * NMC93C46 1024-Bit (64 x 16)
 * NMC93C56 2028 Bit (128 x 16)
 * NMC93C66 4096 Bit (256 x 16)
 * Compatible devices include FM93C46 and others.
 *
 * Other drivers use these interface functions:
 * eeprom93xx_new   - add a new EEPROM (with 16, 64 or 256 words)
 * eeprom93xx_free  - destroy EEPROM
 * eeprom93xx_read  - read data from the EEPROM
 * eeprom93xx_write - write data to the EEPROM
 * eeprom93xx_data  - get EEPROM data array for external manipulation
 *
 * Todo list:
 * - No emulation of EEPROM timings.
 */

#include <assert.h>
#include "eeprom93xx.h"

/* Debug EEPROM emulation. */
//~ #define DEBUG_EEPROM

#ifdef DEBUG_EEPROM
#define logout(fmt, args...) fprintf(stderr, "EEPROM\t%-24s" fmt, __func__, ##args)
#else
#define logout(fmt, args...) ((void)0)
#endif

static int eeprom_instance = 0;
static const int eeprom_version = 20061112;

#if 0
typedef enum {
  eeprom_read  = 0x80,   /* read register xx */
  eeprom_write = 0x40,   /* write register xx */
  eeprom_erase = 0xc0,   /* erase register xx */
  eeprom_ewen  = 0x30,   /* erase / write enable */
  eeprom_ewds  = 0x00,   /* erase / write disable */
  eeprom_eral  = 0x20,   /* erase all registers */
  eeprom_wral  = 0x10,   /* write all registers */
  eeprom_amask = 0x0f,
  eeprom_imask = 0xf0
} eeprom_instruction_t;
#endif

#ifdef DEBUG_EEPROM
static const char *opstring[] = {
  "extended", "write", "read", "erase"
};
#endif

struct _eeprom_t {
    uint8_t  tick;
    uint8_t  address;
    uint8_t  command;
    uint8_t  writeable;

    uint8_t eecs;
    uint8_t eesk;
    uint8_t eedo;

    uint8_t  addrbits;
    uint8_t  size;
    uint16_t data;
    uint16_t contents[0];
};

/* Code for saving and restoring of EEPROM state. */

static void eeprom_save(QEMUFile *f, void *opaque)
{
    /* Save EEPROM data. */
    unsigned address;
    eeprom_t *eeprom = (eeprom_t *)opaque;
    qemu_put_buffer(f, (uint8_t *)eeprom, sizeof(*eeprom) - 2);
    qemu_put_be16(f, eeprom->data);
    for (address = 0; address < eeprom->size; address++) {
        qemu_put_be16(f, eeprom->contents[address]);
    }
}

static int eeprom_load(QEMUFile *f, void *opaque, int version_id)
{
    /* Load EEPROM data from saved data if version and EEPROM size
       of data and current EEPROM are identical. */
    eeprom_t *eeprom = (eeprom_t *)opaque;
    int result = -EINVAL;
    if (version_id == eeprom_version) {
        unsigned address;
        uint8_t size = eeprom->size;
        qemu_get_buffer(f, (uint8_t *)eeprom, sizeof(*eeprom) - 2);
        if (eeprom->size == size) {
            eeprom->data = qemu_get_be16(f);
            for (address = 0; address < eeprom->size; address++) {
                eeprom->contents[address] = qemu_get_be16(f);
            }
            result = 0;
        }
    }
    return result;
}

void eeprom93xx_write(eeprom_t *eeprom, int eecs, int eesk, int eedi)
{
    uint8_t tick = eeprom->tick;
    uint8_t eedo = eeprom->eedo;
    uint16_t address = eeprom->address;
    uint8_t command = eeprom->command;

    logout("CS=%u SK=%u DI=%u DO=%u, tick = %u\n",
           eecs, eesk, eedi, eedo, tick);

    if (! eeprom->eecs && eecs) {
        /* Start chip select cycle. */
        logout("Cycle start, waiting for 1st start bit (0)\n");
        tick = 0;
        command = 0x0;
        address = 0x0;
    } else if (eeprom->eecs && ! eecs) {
        /* End chip select cycle. This triggers write / erase. */
        if (eeprom->writeable) {
            uint8_t subcommand = address >> (eeprom->addrbits - 2);
            if (command == 0 && subcommand == 2) {
                /* Erase all. */
                for (address = 0; address < eeprom->size; address++) {
                    eeprom->contents[address] = 0xffff;
                }
            } else if (command == 3) {
                /* Erase word. */
                eeprom->contents[address] = 0xffff;
            } else if (tick >= 2 + 2 + eeprom->addrbits + 16) {
                if (command == 1) {
                    /* Write word. */
                    eeprom->contents[address] &= eeprom->data;
                } else if (command == 0 && subcommand == 1) {
                    /* Write all. */
                    for (address = 0; address < eeprom->size; address++) {
                        eeprom->contents[address] &= eeprom->data;
                    }
                }
            }
        }
        /* Output DO is tristate, read results in 1. */
        eedo = 1;
    } else if (eecs && ! eeprom->eesk && eesk) {
        /* Raising edge of clock shifts data in. */
        if (tick == 0) {
            /* Wait for 1st start bit. */
            if (eedi == 0) {
                logout("Got correct 1st start bit, waiting for 2nd start bit (1)\n");
                tick++;
            } else {
                logout("wrong 1st start bit (is 1, should be 0)\n");
                tick = 2;
                //~ assert(!"wrong start bit");
            }
        } else if (tick == 1) {
            /* Wait for 2nd start bit. */
            if (eedi != 0) {
                logout("Got correct 2nd start bit, getting command + address\n");
                tick++;
            } else {
                logout("1st start bit is longer than needed\n");
            }
        } else if (tick < 2 + 2) {
            /* Got 2 start bits, transfer 2 opcode bits. */
            tick++;
            command <<= 1;
            if (eedi) {
                command += 1;
            }
        } else if (tick < 2 + 2 + eeprom->addrbits) {
            /* Got 2 start bits and 2 opcode bits, transfer all address bits. */
            tick++;
            address = ((address << 1) | eedi);
            if (tick == 2 + 2 + eeprom->addrbits) {
                logout("%s command, address = 0x%02x (value 0x%04x)\n",
                       opstring[command], address, eeprom->contents[address]);
                if (command == 2) {
                    eedo = 0;
                }
                address = address % eeprom->size;
                if (command == 0) {
                    /* Command code in upper 2 bits of address. */
                    switch (address >> (eeprom->addrbits - 2)) {
                        case 0:
                            logout("write disable command\n");
                            eeprom->writeable = 0;
                            break;
                        case 1:
                            logout("write all command\n");
                            break;
                        case 2:
                            logout("erase all command\n");
                            break;
                        case 3:
                            logout("write enable command\n");
                            eeprom->writeable = 1;
                            break;
                    }
                } else {
                    /* Read, write or erase word. */
                    eeprom->data = eeprom->contents[address];
                }
            }
        } else if (tick < 2 + 2 + eeprom->addrbits + 16) {
            /* Transfer 16 data bits. */
            tick++;
            if (command == 2) {
                /* Read word. */
                eedo = ((eeprom->data & 0x8000) != 0);
            }
            eeprom->data <<= 1;
            eeprom->data += eedi;
        } else {
            logout("additional unneeded tick, not processed\n");
        }
    }
    /* Save status of EEPROM. */
    eeprom->tick = tick;
    eeprom->eecs = eecs;
    eeprom->eesk = eesk;
    eeprom->eedo = eedo;
    eeprom->address = address;
    eeprom->command = command;
}

uint16_t eeprom93xx_read(eeprom_t *eeprom)
{
    /* Return status of pin DO (0 or 1). */
    logout("CS=%u DO=%u\n", eeprom->eecs, eeprom->eedo);
    return (eeprom->eedo);
}

#if 0
void eeprom93xx_reset(eeprom_t *eeprom)
{
    /* prepare eeprom */
    logout("eeprom = 0x%p\n", eeprom);
    eeprom->tick = 0;
    eeprom->command = 0;
}
#endif

eeprom_t *eeprom93xx_new(uint16_t nwords)
{
    /* Add a new EEPROM (with 16, 64 or 256 words). */
    eeprom_t *eeprom;
    uint8_t addrbits;

    switch (nwords) {
        case 16:
        case 64:
            addrbits = 6;
            break;
        case 128:
        case 256:
            addrbits = 8;
            break;
        default:
            assert(!"Unsupported EEPROM size, fallback to 64 words!");
            nwords = 64;
            addrbits = 6;
    }

    eeprom = (eeprom_t *)qemu_mallocz(sizeof(*eeprom) + nwords * 2);
    eeprom->size = nwords;
    eeprom->addrbits = addrbits;
    /* Output DO is tristate, read results in 1. */
    eeprom->eedo = 1;
    logout("eeprom = 0x%p, nwords = %u\n", eeprom, nwords);
    register_savevm("eeprom", eeprom_instance, eeprom_version,
                    eeprom_save, eeprom_load, eeprom);
    return eeprom;
}

void eeprom93xx_free(eeprom_t *eeprom)
{
    /* Destroy EEPROM. */
    logout("eeprom = 0x%p\n", eeprom);
    qemu_free(eeprom);
}

uint16_t *eeprom93xx_data(eeprom_t *eeprom)
{
    /* Get EEPROM data array. */
    return &eeprom->contents[0];
}

/* eof */