/*
* QEMU EEPROM 93xx emulation
*
* Copyright (c) 2006-2007 Stefan Weil
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/* Emulation for serial EEPROMs:
* NMC93C06 256-Bit (16 x 16)
* NMC93C46 1024-Bit (64 x 16)
* NMC93C56 2028 Bit (128 x 16)
* NMC93C66 4096 Bit (256 x 16)
* Compatible devices include FM93C46 and others.
*
* Other drivers use these interface functions:
* eeprom93xx_new - add a new EEPROM (with 16, 64 or 256 words)
* eeprom93xx_free - destroy EEPROM
* eeprom93xx_read - read data from the EEPROM
* eeprom93xx_write - write data to the EEPROM
* eeprom93xx_data - get EEPROM data array for external manipulation
*
* Todo list:
* - No emulation of EEPROM timings.
*/
#include <assert.h>
#include "hw.h"
#include "eeprom93xx.h"
/* Debug EEPROM emulation. */
//~ #define DEBUG_EEPROM
#ifdef DEBUG_EEPROM
#define logout(fmt, args...) fprintf(stderr, "EEPROM\t%-24s" fmt, __func__, ##args)
#else
#define logout(fmt, args...) ((void)0)
#endif
static int eeprom_instance = 0;
static const int eeprom_version = 20061112;
#if 0
typedef enum {
eeprom_read = 0x80, /* read register xx */
eeprom_write = 0x40, /* write register xx */
eeprom_erase = 0xc0, /* erase register xx */
eeprom_ewen = 0x30, /* erase / write enable */
eeprom_ewds = 0x00, /* erase / write disable */
eeprom_eral = 0x20, /* erase all registers */
eeprom_wral = 0x10, /* write all registers */
eeprom_amask = 0x0f,
eeprom_imask = 0xf0
} eeprom_instruction_t;
#endif
#ifdef DEBUG_EEPROM
static const char *opstring[] = {
"extended", "write", "read", "erase"
};
#endif
struct _eeprom_t {
uint8_t tick;
uint8_t address;
uint8_t command;
uint8_t writeable;
uint8_t eecs;
uint8_t eesk;
uint8_t eedo;
uint8_t addrbits;
uint8_t size;
uint16_t data;
uint16_t contents[0];
};
/* Code for saving and restoring of EEPROM state. */
static void eeprom_save(QEMUFile *f, void *opaque)
{
/* Save EEPROM data. */
unsigned address;
eeprom_t *eeprom = (eeprom_t *)opaque;
qemu_put_buffer(f, (uint8_t *)eeprom, sizeof(*eeprom) - 2);
qemu_put_be16(f, eeprom->data);
for (address = 0; address < eeprom->size; address++) {
qemu_put_be16(f, eeprom->contents[address]);
}
}
static int eeprom_load(QEMUFile *f, void *opaque, int version_id)
{
/* Load EEPROM data from saved data if version and EEPROM size
of data and current EEPROM are identical. */
eeprom_t *eeprom = (eeprom_t *)opaque;
int result = -EINVAL;
if (version_id == eeprom_version) {
unsigned address;
uint8_t size = eeprom->size;
qemu_get_buffer(f, (uint8_t *)eeprom, sizeof(*eeprom) - 2);
if (eeprom->size == size) {
eeprom->data = qemu_get_be16(f);
for (address = 0; address < eeprom->size; address++) {
eeprom->contents[address] = qemu_get_be16(f);
}
result = 0;
}
}
return result;
}
void eeprom93xx_write(eeprom_t *eeprom, int eecs, int eesk, int eedi)
{
uint8_t tick = eeprom->tick;
uint8_t eedo = eeprom->eedo;
uint16_t address = eeprom->address;
uint8_t command = eeprom->command;
logout("CS=%u SK=%u DI=%u DO=%u, tick = %u\n",
eecs, eesk, eedi, eedo, tick);
if (! eeprom->eecs && eecs) {
/* Start chip select cycle. */
logout("Cycle start, waiting for 1st start bit (0)\n");
tick = 0;
command = 0x0;
address = 0x0;
} else if (eeprom->eecs && ! eecs) {
/* End chip select cycle. This triggers write / erase. */
if (eeprom->writeable) {
uint8_t subcommand = address >> (eeprom->addrbits - 2);
if (command == 0 && subcommand == 2) {
/* Erase all. */
for (address = 0; address < eeprom->size; address++) {
eeprom->contents[address] = 0xffff;
}
} else if (command == 3) {
/* Erase word. */
eeprom->contents[address] = 0xffff;
} else if (tick >= 2 + 2 + eeprom->addrbits + 16) {
if (command == 1) {
/* Write word. */
eeprom->contents[address] &= eeprom->data;
} else if (command == 0 && subcommand == 1) {
/* Write all. */
for (address = 0; address < eeprom->size; address++) {
eeprom->contents[address] &= eeprom->data;
}
}
}
}
/* Output DO is tristate, read results in 1. */
eedo = 1;
} else if (eecs && ! eeprom->eesk && eesk) {
/* Raising edge of clock shifts data in. */
if (tick == 0) {
/* Wait for 1st start bit. */
if (eedi == 0) {
logout("Got correct 1st start bit, waiting for 2nd start bit (1)\n");
tick++;
} else {
logout("wrong 1st start bit (is 1, should be 0)\n");
tick = 2;
//~ assert(!"wrong start bit");
}
} else if (tick == 1) {
/* Wait for 2nd start bit. */
if (eedi != 0) {
logout("Got correct 2nd start bit, getting command + address\n");
tick++;
} else {
logout("1st start bit is longer than needed\n");
}
} else if (tick < 2 + 2) {
/* Got 2 start bits, transfer 2 opcode bits. */
tick++;
command <<= 1;
if (eedi) {
command += 1;
}
} else if (tick < 2 + 2 + eeprom->addrbits) {
/* Got 2 start bits and 2 opcode bits, transfer all address bits. */
tick++;
address = ((address << 1) | eedi);
if (tick == 2 + 2 + eeprom->addrbits) {
logout("%s command, address = 0x%02x (value 0x%04x)\n",
opstring[command], address, eeprom->contents[address]);
if (command == 2) {
eedo = 0;
}
address = address % eeprom->size;
if (command == 0) {
/* Command code in upper 2 bits of address. */
switch (address >> (eeprom->addrbits - 2)) {
case 0:
logout("write disable command\n");
eeprom->writeable = 0;
break;
case 1:
logout("write all command\n");
break;
case 2:
logout("erase all command\n");
break;
case 3:
logout("write enable command\n");
eeprom->writeable = 1;
break;
}
} else {
/* Read, write or erase word. */
eeprom->data = eeprom->contents[address];
}
}
} else if (tick < 2 + 2 + eeprom->addrbits + 16) {
/* Transfer 16 data bits. */
tick++;
if (command == 2) {
/* Read word. */
eedo = ((eeprom->data & 0x8000) != 0);
}
eeprom->data <<= 1;
eeprom->data += eedi;
} else {
logout("additional unneeded tick, not processed\n");
}
}
/* Save status of EEPROM. */
eeprom->tick = tick;
eeprom->eecs = eecs;
eeprom->eesk = eesk;
eeprom->eedo = eedo;
eeprom->address = address;
eeprom->command = command;
}
uint16_t eeprom93xx_read(eeprom_t *eeprom)
{
/* Return status of pin DO (0 or 1). */
logout("CS=%u DO=%u\n", eeprom->eecs, eeprom->eedo);
return (eeprom->eedo);
}
#if 0
void eeprom93xx_reset(eeprom_t *eeprom)
{
/* prepare eeprom */
logout("eeprom = 0x%p\n", eeprom);
eeprom->tick = 0;
eeprom->command = 0;
}
#endif
eeprom_t *eeprom93xx_new(uint16_t nwords)
{
/* Add a new EEPROM (with 16, 64 or 256 words). */
eeprom_t *eeprom;
uint8_t addrbits;
switch (nwords) {
case 16:
case 64:
addrbits = 6;
break;
case 128:
case 256:
addrbits = 8;
break;
default:
assert(!"Unsupported EEPROM size, fallback to 64 words!");
nwords = 64;
addrbits = 6;
}
eeprom = (eeprom_t *)qemu_mallocz(sizeof(*eeprom) + nwords * 2);
eeprom->size = nwords;
eeprom->addrbits = addrbits;
/* Output DO is tristate, read results in 1. */
eeprom->eedo = 1;
logout("eeprom = 0x%p, nwords = %u\n", eeprom, nwords);
register_savevm("eeprom", eeprom_instance, eeprom_version,
eeprom_save, eeprom_load, eeprom);
return eeprom;
}
void eeprom93xx_free(eeprom_t *eeprom)
{
/* Destroy EEPROM. */
logout("eeprom = 0x%p\n", eeprom);
qemu_free(eeprom);
}
uint16_t *eeprom93xx_data(eeprom_t *eeprom)
{
/* Get EEPROM data array. */
return &eeprom->contents[0];
}
/* eof */
