hw/eeprom24c0x.c

   1 /*
   2  * QEMU EEPROM 24c0x emulation
   3  *
   4  * Copyright (c) 2009 Michel Pollet <buserror@gmail.com>
   5  * Copyright (c) 2006 Aurelien Jarno
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  20  */
  21
  22 #include <assert.h>
  23 #include "hw.h"
  24 #include "eeprom24c0x.h"
  25
  26 /*
  27  * EEPROM 24C01 / 24C02 emulation.
  28  *
  29  * Emulation for serial EEPROMs:
  30  * 24C01 - 1024 bit (128 x 8)
  31  * 24C02 - 2048 bit (256 x 8)
  32  * 24C04 - 4096 bit (512 x 8)
  33  * 24C08 - 8192 bit (1024 x 8)
  34  *
  35  * Typical device names include Microchip 24C02SC or SGS Thomson ST24C02.
  36  */
  37
  38 #define DEBUG
  39
  40 #if defined(DEBUG)
  41 #  define logout(fmt, args...) fprintf(stderr, "24C\t%-24s" fmt, __func__, ##args)
  42 #else
  43 #  define logout(fmt, args...) ((void)0)
  44 #endif
  45
  46 struct _eeprom24c0x_t {
  47         uint8_t kind;
  48         uint8_t tick;
  49         uint8_t address;
  50         uint8_t command;
  51         uint8_t ack;
  52         uint8_t scl;
  53         uint8_t sda;
  54         uint8_t data;
  55         //~ uint16_t size;
  56         uint8_t contents[1024];
  57 };
  58
  59 //typedef struct _eeprom24c0x_t eeprom24c0x_t;
  60
  61
  62 eeprom24c0x_t * eeprom24c0x_new(int eeprom_kind)
  63 {
  64     eeprom24c0x_t *eeprom = (eeprom24c0x_t *)qemu_mallocz(sizeof(eeprom24c0x_t));
  65
  66         eeprom->kind = eeprom_kind;
  67     memset(eeprom->contents, 0xff, sizeof(eeprom->contents));
  68     return eeprom;
  69 }
  70
  71 void eeprom24c0x_free(eeprom24c0x_t *eeprom)
  72 {
  73     logout("eeprom = 0x%p\n", eeprom);
  74     qemu_free(eeprom);
  75 }
  76
  77 uint8_t *eeprom24c0x_data(eeprom24c0x_t *eeprom)
  78 {
  79         return eeprom->contents;
  80 }
  81
  82 uint8_t eeprom24c0x_read(eeprom24c0x_t * eeprom)
  83 {
  84     logout("%u: scl = %u, sda = %u, data = 0x%02x\n",
  85         eeprom->tick, eeprom->scl, eeprom->sda, eeprom->data);
  86     return eeprom->sda;
  87 }
  88
  89 void eeprom24c0x_write(eeprom24c0x_t * eeprom, int scl, int sda)
  90 {
  91     if (eeprom->scl && scl && (eeprom->sda != sda)) {
  92         logout("%u: scl = %u->%u, sda = %u->%u i2c %s\n",
  93                 eeprom->tick, eeprom->scl, scl, eeprom->sda, sda, sda ? "stop" : "start");
  94         if (!sda) {
  95             eeprom->tick = 1;
  96             eeprom->command = 0;
  97         }
  98     } else if (eeprom->tick == 0 && !eeprom->ack) {
  99         /* Waiting for start. */
 100         logout("%u: scl = %u->%u, sda = %u->%u wait for i2c start\n",
 101                 eeprom->tick, eeprom->scl, scl, eeprom->sda, sda);
 102     } else if (!eeprom->scl && scl) {
 103         logout("%u: scl = %u->%u, sda = %u->%u trigger bit\n",
 104                 eeprom->tick, eeprom->scl, scl, eeprom->sda, sda);
 105         if (eeprom->ack) {
 106             logout("\ti2c ack bit = 0\n");
 107             sda = 0;
 108             eeprom->ack = 0;
 109         } else if (eeprom->sda == sda) {
 110             uint8_t bit = (sda != 0);
 111             logout("\ti2c bit = %d\n", bit);
 112             if (eeprom->tick < 9) {
 113                 eeprom->command <<= 1;
 114                 eeprom->command += bit;
 115                 eeprom->tick++;
 116                 if (eeprom->tick == 9) {
 117                     logout("\tcommand 0x%04x, %s\n", eeprom->command, bit ? "read" : "write");
 118                     eeprom->ack = 1;
 119                 }
 120             } else if (eeprom->tick < 17) {
 121                 if (eeprom->command & 1) {
 122                     sda = ((eeprom->data & 0x80) != 0);
 123                 }
 124                 eeprom->address <<= 1;
 125                 eeprom->address += bit;
 126                 eeprom->tick++;
 127                 eeprom->data <<= 1;
 128                 if (eeprom->tick == 17) {
 129                     eeprom->data = eeprom->contents[eeprom->address];
 130                     logout("\taddress 0x%04x, data 0x%02x\n", eeprom->address, eeprom->data);
 131                     eeprom->ack = 1;
 132                     eeprom->tick = 0;
 133                 }
 134             } else if (eeprom->tick >= 17) {
 135                 sda = 0;
 136             }
 137         } else {
 138             logout("\tsda changed with raising scl\n");
 139         }
 140     } else {
 141         logout("%u: scl = %u->%u, sda = %u->%u\n", eeprom->tick, eeprom->scl, scl, eeprom->sda, sda);
 142     }
 143     eeprom->scl = scl;
 144     eeprom->sda = sda;
 145 }