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