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 static int eeprom_instance = 0;
  53 static const int eeprom_version = 20061112;
  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     uint8_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     qemu_put_buffer(f, (uint8_t *)eeprom, sizeof(*eeprom) - 2);
  99     qemu_put_be16(f, eeprom->data);
 100     for (address = 0; address < eeprom->size; address++) {
 101         qemu_put_be16(f, eeprom->contents[address]);
 102     }
 103 }
 104
 105 static int eeprom_load(QEMUFile *f, void *opaque, int version_id)
 106 {
 107     /* Load EEPROM data from saved data if version and EEPROM size
 108        of data and current EEPROM are identical. */
 109     eeprom_t *eeprom = (eeprom_t *)opaque;
 110     int result = -EINVAL;
 111     if (version_id == eeprom_version) {
 112         unsigned address;
 113         uint8_t size = eeprom->size;
 114         qemu_get_buffer(f, (uint8_t *)eeprom, sizeof(*eeprom) - 2);
 115         if (eeprom->size == size) {
 116             eeprom->data = qemu_get_be16(f);
 117             for (address = 0; address < eeprom->size; address++) {
 118                 eeprom->contents[address] = qemu_get_be16(f);
 119             }
 120             result = 0;
 121         }
 122     }
 123     return result;
 124 }
 125
 126 void eeprom93xx_write(eeprom_t *eeprom, int eecs, int eesk, int eedi)
 127 {
 128     uint8_t tick = eeprom->tick;
 129     uint8_t eedo = eeprom->eedo;
 130     uint16_t address = eeprom->address;
 131     uint8_t command = eeprom->command;
 132
 133     logout("CS=%u SK=%u DI=%u DO=%u, tick = %u\n",
 134            eecs, eesk, eedi, eedo, tick);
 135
 136     if (! eeprom->eecs && eecs) {
 137         /* Start chip select cycle. */
 138         logout("Cycle start, waiting for 1st start bit (0)\n");
 139         tick = 0;
 140         command = 0x0;
 141         address = 0x0;
 142     } else if (eeprom->eecs && ! eecs) {
 143         /* End chip select cycle. This triggers write / erase. */
 144         if (eeprom->writeable) {
 145             uint8_t subcommand = address >> (eeprom->addrbits - 2);
 146             if (command == 0 && subcommand == 2) {
 147                 /* Erase all. */
 148                 for (address = 0; address < eeprom->size; address++) {
 149                     eeprom->contents[address] = 0xffff;
 150                 }
 151             } else if (command == 3) {
 152                 /* Erase word. */
 153                 eeprom->contents[address] = 0xffff;
 154             } else if (tick >= 2 + 2 + eeprom->addrbits + 16) {
 155                 if (command == 1) {
 156                     /* Write word. */
 157                     eeprom->contents[address] &= eeprom->data;
 158                 } else if (command == 0 && subcommand == 1) {
 159                     /* Write all. */
 160                     for (address = 0; address < eeprom->size; address++) {
 161                         eeprom->contents[address] &= eeprom->data;
 162                     }
 163                 }
 164             }
 165         }
 166         /* Output DO is tristate, read results in 1. */
 167         eedo = 1;
 168     } else if (eecs && ! eeprom->eesk && eesk) {
 169         /* Raising edge of clock shifts data in. */
 170         if (tick == 0) {
 171             /* Wait for 1st start bit. */
 172             if (eedi == 0) {
 173                 logout("Got correct 1st start bit, waiting for 2nd start bit (1)\n");
 174                 tick++;
 175             } else {
 176                 logout("wrong 1st start bit (is 1, should be 0)\n");
 177                 tick = 2;
 178                 //~ assert(!"wrong start bit");
 179             }
 180         } else if (tick == 1) {
 181             /* Wait for 2nd start bit. */
 182             if (eedi != 0) {
 183                 logout("Got correct 2nd start bit, getting command + address\n");
 184                 tick++;
 185             } else {
 186                 logout("1st start bit is longer than needed\n");
 187             }
 188         } else if (tick < 2 + 2) {
 189             /* Got 2 start bits, transfer 2 opcode bits. */
 190             tick++;
 191             command <<= 1;
 192             if (eedi) {
 193                 command += 1;
 194             }
 195         } else if (tick < 2 + 2 + eeprom->addrbits) {
 196             /* Got 2 start bits and 2 opcode bits, transfer all address bits. */
 197             tick++;
 198             address = ((address << 1) | eedi);
 199             if (tick == 2 + 2 + eeprom->addrbits) {
 200                 logout("%s command, address = 0x%02x (value 0x%04x)\n",
 201                        opstring[command], address, eeprom->contents[address]);
 202                 if (command == 2) {
 203                     eedo = 0;
 204                 }
 205                 address = address % eeprom->size;
 206                 if (command == 0) {
 207                     /* Command code in upper 2 bits of address. */
 208                     switch (address >> (eeprom->addrbits - 2)) {
 209                         case 0:
 210                             logout("write disable command\n");
 211                             eeprom->writeable = 0;
 212                             break;
 213                         case 1:
 214                             logout("write all command\n");
 215                             break;
 216                         case 2:
 217                             logout("erase all command\n");
 218                             break;
 219                         case 3:
 220                             logout("write enable command\n");
 221                             eeprom->writeable = 1;
 222                             break;
 223                     }
 224                 } else {
 225                     /* Read, write or erase word. */
 226                     eeprom->data = eeprom->contents[address];
 227                 }
 228             }
 229         } else if (tick < 2 + 2 + eeprom->addrbits + 16) {
 230             /* Transfer 16 data bits. */
 231             tick++;
 232             if (command == 2) {
 233                 /* Read word. */
 234                 eedo = ((eeprom->data & 0x8000) != 0);
 235             }
 236             eeprom->data <<= 1;
 237             eeprom->data += eedi;
 238         } else {
 239             logout("additional unneeded tick, not processed\n");
 240         }
 241     }
 242     /* Save status of EEPROM. */
 243     eeprom->tick = tick;
 244     eeprom->eecs = eecs;
 245     eeprom->eesk = eesk;
 246     eeprom->eedo = eedo;
 247     eeprom->address = address;
 248     eeprom->command = command;
 249 }
 250
 251 uint16_t eeprom93xx_read(eeprom_t *eeprom)
 252 {
 253     /* Return status of pin DO (0 or 1). */
 254     logout("CS=%u DO=%u\n", eeprom->eecs, eeprom->eedo);
 255     return (eeprom->eedo);
 256 }
 257
 258 #if 0
 259 void eeprom93xx_reset(eeprom_t *eeprom)
 260 {
 261     /* prepare eeprom */
 262     logout("eeprom = 0x%p\n", eeprom);
 263     eeprom->tick = 0;
 264     eeprom->command = 0;
 265 }
 266 #endif
 267
 268 eeprom_t *eeprom93xx_new(uint16_t nwords)
 269 {
 270     /* Add a new EEPROM (with 16, 64 or 256 words). */
 271     eeprom_t *eeprom;
 272     uint8_t addrbits;
 273
 274     switch (nwords) {
 275         case 16:
 276         case 64:
 277             addrbits = 6;
 278             break;
 279         case 128:
 280         case 256:
 281             addrbits = 8;
 282             break;
 283         default:
 284             assert(!"Unsupported EEPROM size, fallback to 64 words!");
 285             nwords = 64;
 286             addrbits = 6;
 287     }
 288
 289     eeprom = (eeprom_t *)qemu_mallocz(sizeof(*eeprom) + nwords * 2);
 290     eeprom->size = nwords;
 291     eeprom->addrbits = addrbits;
 292     /* Output DO is tristate, read results in 1. */
 293     eeprom->eedo = 1;
 294     logout("eeprom = 0x%p, nwords = %u\n", eeprom, nwords);
 295     register_savevm("eeprom", eeprom_instance, eeprom_version,
 296                     eeprom_save, eeprom_load, eeprom);
 297     return eeprom;
 298 }
 299
 300 void eeprom93xx_free(eeprom_t *eeprom)
 301 {
 302     /* Destroy EEPROM. */
 303     logout("eeprom = 0x%p\n", eeprom);
 304     qemu_free(eeprom);
 305 }
 306
 307 uint16_t *eeprom93xx_data(eeprom_t *eeprom)
 308 {
 309     /* Get EEPROM data array. */
 310     return &eeprom->contents[0];
 311 }
 312
 313 /* eof */