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, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  19  */
  20
  21 /* Emulation for serial EEPROMs:
  22  * NMC93C06 256-Bit (16 x 16)
  23  * NMC93C46 1024-Bit (64 x 16)
  24  * NMC93C56 2028 Bit (128 x 16)
  25  * NMC93C66 4096 Bit (256 x 16)
  26  * Compatible devices include FM93C46 and others.
  27  *
  28  * Other drivers use these interface functions:
  29  * eeprom93xx_new   - add a new EEPROM (with 16, 64 or 256 words)
  30  * eeprom93xx_free  - destroy EEPROM
  31  * eeprom93xx_read  - read data from the EEPROM
  32  * eeprom93xx_write - write data to the EEPROM
  33  * eeprom93xx_data  - get EEPROM data array for external manipulation
  34  *
  35  * Todo list:
  36  * - No emulation of EEPROM timings.
  37  */
  38
  39 #include <assert.h>
  40 #include "hw.h"
  41 #include "eeprom93xx.h"
  42
  43 /* Debug EEPROM emulation. */
  44 //~ #define DEBUG_EEPROM
  45
  46 #ifdef DEBUG_EEPROM
  47 #define logout(fmt, args...) fprintf(stderr, "EEPROM\t%-24s" fmt, __func__, ##args)
  48 #else
  49 #define logout(fmt, args...) ((void)0)
  50 #endif
  51
  52 #define EEPROM_INSTANCE  0
  53 #define OLD_EEPROM_VERSION 20061112
  54 #define EEPROM_VERSION (OLD_EEPROM_VERSION + 1)
  55
  56 #if 0
  57 typedef enum {
  58   eeprom_read  = 0x80,   /* read register xx */
  59   eeprom_write = 0x40,   /* write register xx */
  60   eeprom_erase = 0xc0,   /* erase register xx */
  61   eeprom_ewen  = 0x30,   /* erase / write enable */
  62   eeprom_ewds  = 0x00,   /* erase / write disable */
  63   eeprom_eral  = 0x20,   /* erase all registers */
  64   eeprom_wral  = 0x10,   /* write all registers */
  65   eeprom_amask = 0x0f,
  66   eeprom_imask = 0xf0
  67 } eeprom_instruction_t;
  68 #endif
  69
  70 #ifdef DEBUG_EEPROM
  71 static const char *opstring[] = {
  72   "extended", "write", "read", "erase"
  73 };
  74 #endif
  75
  76 struct _eeprom_t {
  77     uint8_t  tick;
  78     uint8_t  address;
  79     uint8_t  command;
  80     uint8_t  writeable;
  81
  82     uint8_t eecs;
  83     uint8_t eesk;
  84     uint8_t eedo;
  85
  86     uint8_t  addrbits;
  87     uint16_t size;
  88     uint16_t data;
  89     uint16_t contents[0];
  90 };
  91
  92 /* Code for saving and restoring of EEPROM state. */
  93
  94 static void eeprom_save(QEMUFile *f, void *opaque)
  95 {
  96     /* Save EEPROM data. */
  97     unsigned address;
  98     eeprom_t *eeprom = (eeprom_t *)opaque;
  99
 100     qemu_put_byte(f, eeprom->tick);
 101     qemu_put_byte(f, eeprom->address);
 102     qemu_put_byte(f, eeprom->command);
 103     qemu_put_byte(f, eeprom->writeable);
 104
 105     qemu_put_byte(f, eeprom->eecs);
 106     qemu_put_byte(f, eeprom->eesk);
 107     qemu_put_byte(f, eeprom->eedo);
 108
 109     qemu_put_byte(f, eeprom->addrbits);
 110     qemu_put_be16(f, eeprom->size);
 111     qemu_put_be16(f, eeprom->data);
 112     for (address = 0; address < eeprom->size; address++) {
 113         qemu_put_be16(f, eeprom->contents[address]);
 114     }
 115 }
 116
 117 static int eeprom_load(QEMUFile *f, void *opaque, int version_id)
 118 {
 119     /* Load EEPROM data from saved data if version and EEPROM size
 120        of data and current EEPROM are identical. */
 121     eeprom_t *eeprom = (eeprom_t *)opaque;
 122     int result = -EINVAL;
 123     if (version_id >= OLD_EEPROM_VERSION) {
 124         unsigned address;
 125         int size = eeprom->size;
 126
 127         eeprom->tick = qemu_get_byte(f);
 128         eeprom->address = qemu_get_byte(f);
 129         eeprom->command = qemu_get_byte(f);
 130         eeprom->writeable = qemu_get_byte(f);
 131
 132         eeprom->eecs = qemu_get_byte(f);
 133         eeprom->eesk = qemu_get_byte(f);
 134         eeprom->eedo = qemu_get_byte(f);
 135
 136         eeprom->addrbits = qemu_get_byte(f);
 137         if (version_id == OLD_EEPROM_VERSION) {
 138             eeprom->size = qemu_get_byte(f);
 139             qemu_get_byte(f);
 140         } else {
 141             eeprom->size = qemu_get_be16(f);
 142         }
 143
 144         if (eeprom->size == size) {
 145             eeprom->data = qemu_get_be16(f);
 146             for (address = 0; address < eeprom->size; address++) {
 147                 eeprom->contents[address] = qemu_get_be16(f);
 148             }
 149             result = 0;
 150         }
 151     }
 152     return result;
 153 }
 154
 155 void eeprom93xx_write(eeprom_t *eeprom, int eecs, int eesk, int eedi)
 156 {
 157     uint8_t tick = eeprom->tick;
 158     uint8_t eedo = eeprom->eedo;
 159     uint16_t address = eeprom->address;
 160     uint8_t command = eeprom->command;
 161
 162     logout("CS=%u SK=%u DI=%u DO=%u, tick = %u\n",
 163            eecs, eesk, eedi, eedo, tick);
 164
 165     if (! eeprom->eecs && eecs) {
 166         /* Start chip select cycle. */
 167         logout("Cycle start, waiting for 1st start bit (0)\n");
 168         tick = 0;
 169         command = 0x0;
 170         address = 0x0;
 171     } else if (eeprom->eecs && ! eecs) {
 172         /* End chip select cycle. This triggers write / erase. */
 173         if (eeprom->writeable) {
 174             uint8_t subcommand = address >> (eeprom->addrbits - 2);
 175             if (command == 0 && subcommand == 2) {
 176                 /* Erase all. */
 177                 for (address = 0; address < eeprom->size; address++) {
 178                     eeprom->contents[address] = 0xffff;
 179                 }
 180             } else if (command == 3) {
 181                 /* Erase word. */
 182                 eeprom->contents[address] = 0xffff;
 183             } else if (tick >= 2 + 2 + eeprom->addrbits + 16) {
 184                 if (command == 1) {
 185                     /* Write word. */
 186                     eeprom->contents[address] &= eeprom->data;
 187                 } else if (command == 0 && subcommand == 1) {
 188                     /* Write all. */
 189                     for (address = 0; address < eeprom->size; address++) {
 190                         eeprom->contents[address] &= eeprom->data;
 191                     }
 192                 }
 193             }
 194         }
 195         /* Output DO is tristate, read results in 1. */
 196         eedo = 1;
 197     } else if (eecs && ! eeprom->eesk && eesk) {
 198         /* Raising edge of clock shifts data in. */
 199         if (tick == 0) {
 200             /* Wait for 1st start bit. */
 201             if (eedi == 0) {
 202                 logout("Got correct 1st start bit, waiting for 2nd start bit (1)\n");
 203                 tick++;
 204             } else {
 205                 logout("wrong 1st start bit (is 1, should be 0)\n");
 206                 tick = 2;
 207                 //~ assert(!"wrong start bit");
 208             }
 209         } else if (tick == 1) {
 210             /* Wait for 2nd start bit. */
 211             if (eedi != 0) {
 212                 logout("Got correct 2nd start bit, getting command + address\n");
 213                 tick++;
 214             } else {
 215                 logout("1st start bit is longer than needed\n");
 216             }
 217         } else if (tick < 2 + 2) {
 218             /* Got 2 start bits, transfer 2 opcode bits. */
 219             tick++;
 220             command <<= 1;
 221             if (eedi) {
 222                 command += 1;
 223             }
 224         } else if (tick < 2 + 2 + eeprom->addrbits) {
 225             /* Got 2 start bits and 2 opcode bits, transfer all address bits. */
 226             tick++;
 227             address = ((address << 1) | eedi);
 228             if (tick == 2 + 2 + eeprom->addrbits) {
 229                 logout("%s command, address = 0x%02x (value 0x%04x)\n",
 230                        opstring[command], address, eeprom->contents[address]);
 231                 if (command == 2) {
 232                     eedo = 0;
 233                 }
 234                 address = address % eeprom->size;
 235                 if (command == 0) {
 236                     /* Command code in upper 2 bits of address. */
 237                     switch (address >> (eeprom->addrbits - 2)) {
 238                         case 0:
 239                             logout("write disable command\n");
 240                             eeprom->writeable = 0;
 241                             break;
 242                         case 1:
 243                             logout("write all command\n");
 244                             break;
 245                         case 2:
 246                             logout("erase all command\n");
 247                             break;
 248                         case 3:
 249                             logout("write enable command\n");
 250                             eeprom->writeable = 1;
 251                             break;
 252                     }
 253                 } else {
 254                     /* Read, write or erase word. */
 255                     eeprom->data = eeprom->contents[address];
 256                 }
 257             }
 258         } else if (tick < 2 + 2 + eeprom->addrbits + 16) {
 259             /* Transfer 16 data bits. */
 260             tick++;
 261             if (command == 2) {
 262                 /* Read word. */
 263                 eedo = ((eeprom->data & 0x8000) != 0);
 264             }
 265             eeprom->data <<= 1;
 266             eeprom->data += eedi;
 267         } else {
 268             logout("additional unneeded tick, not processed\n");
 269         }
 270     }
 271     /* Save status of EEPROM. */
 272     eeprom->tick = tick;
 273     eeprom->eecs = eecs;
 274     eeprom->eesk = eesk;
 275     eeprom->eedo = eedo;
 276     eeprom->address = address;
 277     eeprom->command = command;
 278 }
 279
 280 uint16_t eeprom93xx_read(eeprom_t *eeprom)
 281 {
 282     /* Return status of pin DO (0 or 1). */
 283     logout("CS=%u DO=%u\n", eeprom->eecs, eeprom->eedo);
 284     return (eeprom->eedo);
 285 }
 286
 287 #if 0
 288 void eeprom93xx_reset(eeprom_t *eeprom)
 289 {
 290     /* prepare eeprom */
 291     logout("eeprom = 0x%p\n", eeprom);
 292     eeprom->tick = 0;
 293     eeprom->command = 0;
 294 }
 295 #endif
 296
 297 eeprom_t *eeprom93xx_new(uint16_t nwords)
 298 {
 299     /* Add a new EEPROM (with 16, 64 or 256 words). */
 300     eeprom_t *eeprom;
 301     uint8_t addrbits;
 302
 303     switch (nwords) {
 304         case 16:
 305         case 64:
 306             addrbits = 6;
 307             break;
 308         case 128:
 309         case 256:
 310             addrbits = 8;
 311             break;
 312         default:
 313             assert(!"Unsupported EEPROM size, fallback to 64 words!");
 314             nwords = 64;
 315             addrbits = 6;
 316     }
 317
 318     eeprom = (eeprom_t *)qemu_mallocz(sizeof(*eeprom) + nwords * 2);
 319     eeprom->size = nwords;
 320     eeprom->addrbits = addrbits;
 321     /* Output DO is tristate, read results in 1. */
 322     eeprom->eedo = 1;
 323     logout("eeprom = 0x%p, nwords = %u\n", eeprom, nwords);
 324     register_savevm("eeprom", EEPROM_INSTANCE, EEPROM_VERSION,
 325                     eeprom_save, eeprom_load, eeprom);
 326     return eeprom;
 327 }
 328
 329 void eeprom93xx_free(eeprom_t *eeprom)
 330 {
 331     /* Destroy EEPROM. */
 332     logout("eeprom = 0x%p\n", eeprom);
 333     qemu_free(eeprom);
 334 }
 335
 336 uint16_t *eeprom93xx_data(eeprom_t *eeprom)
 337 {
 338     /* Get EEPROM data array. */
 339     return &eeprom->contents[0];
 340 }
 341
 342 /* eof */