hw/eeprom93xx.c

   1 /*
   2  * QEMU EEPROM 93xx emulation
   3  *
   4  * Copyright (c) 2006-2007 Stefan Weil
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 /* Emulation for serial EEPROMs:
  21  * NMC93C06 256-Bit (16 x 16)
  22  * NMC93C46 1024-Bit (64 x 16)
  23  * NMC93C56 2028 Bit (128 x 16)
  24  * NMC93C66 4096 Bit (256 x 16)
  25  * Compatible devices include FM93C46 and others.
  26  *
  27  * Other drivers use these interface functions:
  28  * eeprom93xx_new   - add a new EEPROM (with 16, 64 or 256 words)
  29  * eeprom93xx_free  - destroy EEPROM
  30  * eeprom93xx_read  - read data from the EEPROM
  31  * eeprom93xx_write - write data to the EEPROM
  32  * eeprom93xx_data  - get EEPROM data array for external manipulation
  33  *
  34  * Todo list:
  35  * - No emulation of EEPROM timings.
  36  */
  37
  38 #include "hw.h"
  39 #include "eeprom93xx.h"
  40
  41 /* Debug EEPROM emulation. */
  42 //~ #define DEBUG_EEPROM
  43
  44 #ifdef DEBUG_EEPROM
  45 #define logout(fmt, ...) fprintf(stderr, "EEPROM\t%-24s" fmt, __func__, ## __VA_ARGS__)
  46 #else
  47 #define logout(fmt, ...) ((void)0)
  48 #endif
  49
  50 #define EEPROM_INSTANCE  0
  51 #define OLD_EEPROM_VERSION 20061112
  52 #define EEPROM_VERSION (OLD_EEPROM_VERSION + 1)
  53
  54 #if 0
  55 typedef enum {
  56   eeprom_read  = 0x80,   /* read register xx */
  57   eeprom_write = 0x40,   /* write register xx */
  58   eeprom_erase = 0xc0,   /* erase register xx */
  59   eeprom_ewen  = 0x30,   /* erase / write enable */
  60   eeprom_ewds  = 0x00,   /* erase / write disable */
  61   eeprom_eral  = 0x20,   /* erase all registers */
  62   eeprom_wral  = 0x10,   /* write all registers */
  63   eeprom_amask = 0x0f,
  64   eeprom_imask = 0xf0
  65 } eeprom_instruction_t;
  66 #endif
  67
  68 #ifdef DEBUG_EEPROM
  69 static const char *opstring[] = {
  70   "extended", "write", "read", "erase"
  71 };
  72 #endif
  73
  74 struct _eeprom_t {
  75     uint8_t  tick;
  76     uint8_t  address;
  77     uint8_t  command;
  78     uint8_t  writeable;
  79
  80     uint8_t eecs;
  81     uint8_t eesk;
  82     uint8_t eedo;
  83
  84     uint8_t  addrbits;
  85     uint16_t size;
  86     uint16_t data;
  87     uint16_t contents[0];
  88 };
  89
  90 /* Code for saving and restoring of EEPROM state. */
  91
  92 static void eeprom_save(QEMUFile *f, void *opaque)
  93 {
  94     /* Save EEPROM data. */
  95     unsigned address;
  96     eeprom_t *eeprom = (eeprom_t *)opaque;
  97
  98     qemu_put_byte(f, eeprom->tick);
  99     qemu_put_byte(f, eeprom->address);
 100     qemu_put_byte(f, eeprom->command);
 101     qemu_put_byte(f, eeprom->writeable);
 102
 103     qemu_put_byte(f, eeprom->eecs);
 104     qemu_put_byte(f, eeprom->eesk);
 105     qemu_put_byte(f, eeprom->eedo);
 106
 107     qemu_put_byte(f, eeprom->addrbits);
 108     qemu_put_be16(f, eeprom->size);
 109     qemu_put_be16(f, eeprom->data);
 110     for (address = 0; address < eeprom->size; address++) {
 111         qemu_put_be16(f, eeprom->contents[address]);
 112     }
 113 }
 114
 115 static int eeprom_load(QEMUFile *f, void *opaque, int version_id)
 116 {
 117     /* Load EEPROM data from saved data if version and EEPROM size
 118        of data and current EEPROM are identical. */
 119     eeprom_t *eeprom = (eeprom_t *)opaque;
 120     int result = -EINVAL;
 121     if (version_id >= OLD_EEPROM_VERSION) {
 122         unsigned address;
 123         int size = eeprom->size;
 124
 125         eeprom->tick = qemu_get_byte(f);
 126         eeprom->address = qemu_get_byte(f);
 127         eeprom->command = qemu_get_byte(f);
 128         eeprom->writeable = qemu_get_byte(f);
 129
 130         eeprom->eecs = qemu_get_byte(f);
 131         eeprom->eesk = qemu_get_byte(f);
 132         eeprom->eedo = qemu_get_byte(f);
 133
 134         eeprom->addrbits = qemu_get_byte(f);
 135         if (version_id == OLD_EEPROM_VERSION) {
 136             eeprom->size = qemu_get_byte(f);
 137             qemu_get_byte(f);
 138         } else {
 139             eeprom->size = qemu_get_be16(f);
 140         }
 141
 142         if (eeprom->size == size) {
 143             eeprom->data = qemu_get_be16(f);
 144             for (address = 0; address < eeprom->size; address++) {
 145                 eeprom->contents[address] = qemu_get_be16(f);
 146             }
 147             result = 0;
 148         }
 149     }
 150     return result;
 151 }
 152
 153 void eeprom93xx_write(eeprom_t *eeprom, int eecs, int eesk, int eedi)
 154 {
 155     uint8_t tick = eeprom->tick;
 156     uint8_t eedo = eeprom->eedo;
 157     uint16_t address = eeprom->address;
 158     uint8_t command = eeprom->command;
 159
 160     logout("CS=%u SK=%u DI=%u DO=%u, tick = %u\n",
 161            eecs, eesk, eedi, eedo, tick);
 162
 163     if (! eeprom->eecs && eecs) {
 164         /* Start chip select cycle. */
 165         logout("Cycle start, waiting for 1st start bit (0)\n");
 166         tick = 0;
 167         command = 0x0;
 168         address = 0x0;
 169     } else if (eeprom->eecs && ! eecs) {
 170         /* End chip select cycle. This triggers write / erase. */
 171         if (eeprom->writeable) {
 172             uint8_t subcommand = address >> (eeprom->addrbits - 2);
 173             if (command == 0 && subcommand == 2) {
 174                 /* Erase all. */
 175                 for (address = 0; address < eeprom->size; address++) {
 176                     eeprom->contents[address] = 0xffff;
 177                 }
 178             } else if (command == 3) {
 179                 /* Erase word. */
 180                 eeprom->contents[address] = 0xffff;
 181             } else if (tick >= 2 + 2 + eeprom->addrbits + 16) {
 182                 if (command == 1) {
 183                     /* Write word. */
 184                     eeprom->contents[address] &= eeprom->data;
 185                 } else if (command == 0 && subcommand == 1) {
 186                     /* Write all. */
 187                     for (address = 0; address < eeprom->size; address++) {
 188                         eeprom->contents[address] &= eeprom->data;
 189                     }
 190                 }
 191             }
 192         }
 193         /* Output DO is tristate, read results in 1. */
 194         eedo = 1;
 195     } else if (eecs && ! eeprom->eesk && eesk) {
 196         /* Raising edge of clock shifts data in. */
 197         if (tick == 0) {
 198             /* Wait for 1st start bit. */
 199             if (eedi == 0) {
 200                 logout("Got correct 1st start bit, waiting for 2nd start bit (1)\n");
 201                 tick++;
 202             } else {
 203                 logout("wrong 1st start bit (is 1, should be 0)\n");
 204                 tick = 2;
 205                 //~ assert(!"wrong start bit");
 206             }
 207         } else if (tick == 1) {
 208             /* Wait for 2nd start bit. */
 209             if (eedi != 0) {
 210                 logout("Got correct 2nd start bit, getting command + address\n");
 211                 tick++;
 212             } else {
 213                 logout("1st start bit is longer than needed\n");
 214             }
 215         } else if (tick < 2 + 2) {
 216             /* Got 2 start bits, transfer 2 opcode bits. */
 217             tick++;
 218             command <<= 1;
 219             if (eedi) {
 220                 command += 1;
 221             }
 222         } else if (tick < 2 + 2 + eeprom->addrbits) {
 223             /* Got 2 start bits and 2 opcode bits, transfer all address bits. */
 224             tick++;
 225             address = ((address << 1) | eedi);
 226             if (tick == 2 + 2 + eeprom->addrbits) {
 227                 logout("%s command, address = 0x%02x (value 0x%04x)\n",
 228                        opstring[command], address, eeprom->contents[address]);
 229                 if (command == 2) {
 230                     eedo = 0;
 231                 }
 232                 address = address % eeprom->size;
 233                 if (command == 0) {
 234                     /* Command code in upper 2 bits of address. */
 235                     switch (address >> (eeprom->addrbits - 2)) {
 236                         case 0:
 237                             logout("write disable command\n");
 238                             eeprom->writeable = 0;
 239                             break;
 240                         case 1:
 241                             logout("write all command\n");
 242                             break;
 243                         case 2:
 244                             logout("erase all command\n");
 245                             break;
 246                         case 3:
 247                             logout("write enable command\n");
 248                             eeprom->writeable = 1;
 249                             break;
 250                     }
 251                 } else {
 252                     /* Read, write or erase word. */
 253                     eeprom->data = eeprom->contents[address];
 254                 }
 255             }
 256         } else if (tick < 2 + 2 + eeprom->addrbits + 16) {
 257             /* Transfer 16 data bits. */
 258             tick++;
 259             if (command == 2) {
 260                 /* Read word. */
 261                 eedo = ((eeprom->data & 0x8000) != 0);
 262             }
 263             eeprom->data <<= 1;
 264             eeprom->data += eedi;
 265         } else {
 266             logout("additional unneeded tick, not processed\n");
 267         }
 268     }
 269     /* Save status of EEPROM. */
 270     eeprom->tick = tick;
 271     eeprom->eecs = eecs;
 272     eeprom->eesk = eesk;
 273     eeprom->eedo = eedo;
 274     eeprom->address = address;
 275     eeprom->command = command;
 276 }
 277
 278 uint16_t eeprom93xx_read(eeprom_t *eeprom)
 279 {
 280     /* Return status of pin DO (0 or 1). */
 281     logout("CS=%u DO=%u\n", eeprom->eecs, eeprom->eedo);
 282     return (eeprom->eedo);
 283 }
 284
 285 #if 0
 286 void eeprom93xx_reset(eeprom_t *eeprom)
 287 {
 288     /* prepare eeprom */
 289     logout("eeprom = 0x%p\n", eeprom);
 290     eeprom->tick = 0;
 291     eeprom->command = 0;
 292 }
 293 #endif
 294
 295 eeprom_t *eeprom93xx_new(uint16_t nwords)
 296 {
 297     /* Add a new EEPROM (with 16, 64 or 256 words). */
 298     eeprom_t *eeprom;
 299     uint8_t addrbits;
 300
 301     switch (nwords) {
 302         case 16:
 303         case 64:
 304             addrbits = 6;
 305             break;
 306         case 128:
 307         case 256:
 308             addrbits = 8;
 309             break;
 310         default:
 311             assert(!"Unsupported EEPROM size, fallback to 64 words!");
 312             nwords = 64;
 313             addrbits = 6;
 314     }
 315
 316     eeprom = (eeprom_t *)qemu_mallocz(sizeof(*eeprom) + nwords * 2);
 317     eeprom->size = nwords;
 318     eeprom->addrbits = addrbits;
 319     /* Output DO is tristate, read results in 1. */
 320     eeprom->eedo = 1;
 321     logout("eeprom = 0x%p, nwords = %u\n", eeprom, nwords);
 322     register_savevm("eeprom", EEPROM_INSTANCE, EEPROM_VERSION,
 323                     eeprom_save, eeprom_load, eeprom);
 324     return eeprom;
 325 }
 326
 327 void eeprom93xx_free(eeprom_t *eeprom)
 328 {
 329     /* Destroy EEPROM. */
 330     logout("eeprom = 0x%p\n", eeprom);
 331     unregister_savevm("eeprom", eeprom);
 332     qemu_free(eeprom);
 333 }
 334
 335 uint16_t *eeprom93xx_data(eeprom_t *eeprom)
 336 {
 337     /* Get EEPROM data array. */
 338     return &eeprom->contents[0];
 339 }
 340
 341 /* eof */