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 "eeprom93xx.h"
  41
  42 /* Debug EEPROM emulation. */
  43 //~ #define DEBUG_EEPROM
  44
  45 #ifdef DEBUG_EEPROM
  46 #define logout(fmt, args...) fprintf(stderr, "EEPROM\t%-24s" fmt, __func__, ##args)
  47 #else
  48 #define logout(fmt, args...) ((void)0)
  49 #endif
  50
  51 static int eeprom_instance = 0;
  52 static const int eeprom_version = 20061112;
  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     uint8_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     qemu_put_buffer(f, (uint8_t *)eeprom, sizeof(*eeprom) - 2);
  98     qemu_put_be16(f, eeprom->data);
  99     for (address = 0; address < eeprom->size; address++) {
 100         qemu_put_be16(f, eeprom->contents[address]);
 101     }
 102 }
 103
 104 static int eeprom_load(QEMUFile *f, void *opaque, int version_id)
 105 {
 106     /* Load EEPROM data from saved data if version and EEPROM size
 107        of data and current EEPROM are identical. */
 108     eeprom_t *eeprom = (eeprom_t *)opaque;
 109     int result = -EINVAL;
 110     if (version_id == eeprom_version) {
 111         unsigned address;
 112         uint8_t size = eeprom->size;
 113         qemu_get_buffer(f, (uint8_t *)eeprom, sizeof(*eeprom) - 2);
 114         if (eeprom->size == size) {
 115             eeprom->data = qemu_get_be16(f);
 116             for (address = 0; address < eeprom->size; address++) {
 117                 eeprom->contents[address] = qemu_get_be16(f);
 118             }
 119             result = 0;
 120         }
 121     }
 122     return result;
 123 }
 124
 125 void eeprom93xx_write(eeprom_t *eeprom, int eecs, int eesk, int eedi)
 126 {
 127     uint8_t tick = eeprom->tick;
 128     uint8_t eedo = eeprom->eedo;
 129     uint16_t address = eeprom->address;
 130     uint8_t command = eeprom->command;
 131
 132     logout("CS=%u SK=%u DI=%u DO=%u, tick = %u\n",
 133            eecs, eesk, eedi, eedo, tick);
 134
 135     if (! eeprom->eecs && eecs) {
 136         /* Start chip select cycle. */
 137         logout("Cycle start, waiting for 1st start bit (0)\n");
 138         tick = 0;
 139         command = 0x0;
 140         address = 0x0;
 141     } else if (eeprom->eecs && ! eecs) {
 142         /* End chip select cycle. This triggers write / erase. */
 143         if (eeprom->writeable) {
 144             uint8_t subcommand = address >> (eeprom->addrbits - 2);
 145             if (command == 0 && subcommand == 2) {
 146                 /* Erase all. */
 147                 for (address = 0; address < eeprom->size; address++) {
 148                     eeprom->contents[address] = 0xffff;
 149                 }
 150             } else if (command == 3) {
 151                 /* Erase word. */
 152                 eeprom->contents[address] = 0xffff;
 153             } else if (tick >= 2 + 2 + eeprom->addrbits + 16) {
 154                 if (command == 1) {
 155                     /* Write word. */
 156                     eeprom->contents[address] &= eeprom->data;
 157                 } else if (command == 0 && subcommand == 1) {
 158                     /* Write all. */
 159                     for (address = 0; address < eeprom->size; address++) {
 160                         eeprom->contents[address] &= eeprom->data;
 161                     }
 162                 }
 163             }
 164         }
 165         /* Output DO is tristate, read results in 1. */
 166         eedo = 1;
 167     } else if (eecs && ! eeprom->eesk && eesk) {
 168         /* Raising edge of clock shifts data in. */
 169         if (tick == 0) {
 170             /* Wait for 1st start bit. */
 171             if (eedi == 0) {
 172                 logout("Got correct 1st start bit, waiting for 2nd start bit (1)\n");
 173                 tick++;
 174             } else {
 175                 logout("wrong 1st start bit (is 1, should be 0)\n");
 176                 tick = 2;
 177                 //~ assert(!"wrong start bit");
 178             }
 179         } else if (tick == 1) {
 180             /* Wait for 2nd start bit. */
 181             if (eedi != 0) {
 182                 logout("Got correct 2nd start bit, getting command + address\n");
 183                 tick++;
 184             } else {
 185                 logout("1st start bit is longer than needed\n");
 186             }
 187         } else if (tick < 2 + 2) {
 188             /* Got 2 start bits, transfer 2 opcode bits. */
 189             tick++;
 190             command <<= 1;
 191             if (eedi) {
 192                 command += 1;
 193             }
 194         } else if (tick < 2 + 2 + eeprom->addrbits) {
 195             /* Got 2 start bits and 2 opcode bits, transfer all address bits. */
 196             tick++;
 197             address = ((address << 1) | eedi);
 198             if (tick == 2 + 2 + eeprom->addrbits) {
 199                 logout("%s command, address = 0x%02x (value 0x%04x)\n",
 200                        opstring[command], address, eeprom->contents[address]);
 201                 if (command == 2) {
 202                     eedo = 0;
 203                 }
 204                 address = address % eeprom->size;
 205                 if (command == 0) {
 206                     /* Command code in upper 2 bits of address. */
 207                     switch (address >> (eeprom->addrbits - 2)) {
 208                         case 0:
 209                             logout("write disable command\n");
 210                             eeprom->writeable = 0;
 211                             break;
 212                         case 1:
 213                             logout("write all command\n");
 214                             break;
 215                         case 2:
 216                             logout("erase all command\n");
 217                             break;
 218                         case 3:
 219                             logout("write enable command\n");
 220                             eeprom->writeable = 1;
 221                             break;
 222                     }
 223                 } else {
 224                     /* Read, write or erase word. */
 225                     eeprom->data = eeprom->contents[address];
 226                 }
 227             }
 228         } else if (tick < 2 + 2 + eeprom->addrbits + 16) {
 229             /* Transfer 16 data bits. */
 230             tick++;
 231             if (command == 2) {
 232                 /* Read word. */
 233                 eedo = ((eeprom->data & 0x8000) != 0);
 234             }
 235             eeprom->data <<= 1;
 236             eeprom->data += eedi;
 237         } else {
 238             logout("additional unneeded tick, not processed\n");
 239         }
 240     }
 241     /* Save status of EEPROM. */
 242     eeprom->tick = tick;
 243     eeprom->eecs = eecs;
 244     eeprom->eesk = eesk;
 245     eeprom->eedo = eedo;
 246     eeprom->address = address;
 247     eeprom->command = command;
 248 }
 249
 250 uint16_t eeprom93xx_read(eeprom_t *eeprom)
 251 {
 252     /* Return status of pin DO (0 or 1). */
 253     logout("CS=%u DO=%u\n", eeprom->eecs, eeprom->eedo);
 254     return (eeprom->eedo);
 255 }
 256
 257 #if 0
 258 void eeprom93xx_reset(eeprom_t *eeprom)
 259 {
 260     /* prepare eeprom */
 261     logout("eeprom = 0x%p\n", eeprom);
 262     eeprom->tick = 0;
 263     eeprom->command = 0;
 264 }
 265 #endif
 266
 267 eeprom_t *eeprom93xx_new(uint16_t nwords)
 268 {
 269     /* Add a new EEPROM (with 16, 64 or 256 words). */
 270     eeprom_t *eeprom;
 271     uint8_t addrbits;
 272
 273     switch (nwords) {
 274         case 16:
 275         case 64:
 276             addrbits = 6;
 277             break;
 278         case 128:
 279         case 256:
 280             addrbits = 8;
 281             break;
 282         default:
 283             assert(!"Unsupported EEPROM size, fallback to 64 words!");
 284             nwords = 64;
 285             addrbits = 6;
 286     }
 287
 288     eeprom = (eeprom_t *)qemu_mallocz(sizeof(*eeprom) + nwords * 2);
 289     eeprom->size = nwords;
 290     eeprom->addrbits = addrbits;
 291     /* Output DO is tristate, read results in 1. */
 292     eeprom->eedo = 1;
 293     logout("eeprom = 0x%p, nwords = %u\n", eeprom, nwords);
 294     register_savevm("eeprom", eeprom_instance, eeprom_version,
 295                     eeprom_save, eeprom_load, eeprom);
 296     return eeprom;
 297 }
 298
 299 void eeprom93xx_free(eeprom_t *eeprom)
 300 {
 301     /* Destroy EEPROM. */
 302     logout("eeprom = 0x%p\n", eeprom);
 303     qemu_free(eeprom);
 304 }
 305
 306 uint16_t *eeprom93xx_data(eeprom_t *eeprom)
 307 {
 308     /* Get EEPROM data array. */
 309     return &eeprom->contents[0];
 310 }
 311
 312 /* eof */