mirror of
https://github.com/ekeeke/Genesis-Plus-GX.git
synced 2024-11-05 02:15:07 +01:00
65 lines
2.3 KiB
C
65 lines
2.3 KiB
C
|
/* this defines the type of EEPROM inside the game cartridge as Backup RAM
|
||
|
|
* Here are some notes from 8BitWizard (http://www.spritesmind.net/_GenDev/forum):
|
||
|
|
*
|
||
|
|
* Mode 1 (7-bit) - the chip takes a single byte with a 7-bit memory address and a R/W bit (24C01)
|
||
|
|
* Mode 2 (8-bit) - the chip takes a 7-bit device address and R/W bit followed by an 8-bit memory address;
|
||
|
|
* the device address may contain up to three more memory address bits (24C01 - 24C16).
|
||
|
|
* You can also string eight 24C01, four 24C02, two 24C08, or various combinations, set their address config lines correctly,
|
||
|
|
* and the result appears exactly the same as a 24C16
|
||
|
|
* Mode 3 (16-bit) - the chip takes a 7-bit device address and R/W bit followed by a 16-bit memory address (24C32 and larger)
|
||
|
|
*
|
||
|
|
* Also, while most 24Cxx are addressed at 200000-2FFFFF, I have found two different ways of mapping the control lines.
|
||
|
|
* EA uses SDA on D7 (read/write) and SCL on D6 (write only), and I have found boards using different mapping (I think Accolade)
|
||
|
|
* which uses D1-read=SDA, D0-write=SDA, D1-write=SCL. Accolade also has a custom-chip mapper which may even use a third method.
|
||
|
|
*/
|
||
|
|
|
||
|
|
typedef struct
|
||
|
|
{
|
||
|
|
uint8 address_bits; /* number of bits needed to address the array: 7, 8 or 16 */
|
||
|
|
uint16 size_mask; /* size of the array (in bytes) - 1 */
|
||
|
|
uint16 pagewrite_mask; /* maximal number of bytes that can be written in a single write cycle - 1*/
|
||
|
|
uint32 sda_in_adr; /* 68k address used by SDA_IN signal */
|
||
|
|
uint32 sda_out_adr; /* 68k address used by SDA_OUT signal */
|
||
|
|
uint32 scl_adr; /* address used by SCL signal */
|
||
|
|
uint8 sda_in_bit; /* position of the SDA_IN bit */
|
||
|
|
uint8 sda_out_bit; /* position of the SDA_OUT bit */
|
||
|
|
uint8 scl_bit; /* position of the SCL bit */
|
||
|
|
|
||
|
|
} T_EEPROM_TYPE;
|
||
|
|
|
||
|
|
typedef enum
|
||
|
|
{
|
||
|
|
STAND_BY = 0,
|
||
|
|
WAIT_STOP,
|
||
|
|
GET_SLAVE_ADR,
|
||
|
|
GET_WORD_ADR_7BITS,
|
||
|
|
GET_WORD_ADR_HIGH,
|
||
|
|
GET_WORD_ADR_LOW,
|
||
|
|
WRITE_DATA,
|
||
|
|
READ_DATA,
|
||
|
|
|
||
|
|
} T_EEPROM_STATE;
|
||
|
|
|
||
|
|
typedef struct
|
||
|
|
{
|
||
|
|
uint8 sda;
|
||
|
|
uint8 scl;
|
||
|
|
uint8 old_sda;
|
||
|
|
uint8 old_scl;
|
||
|
|
uint8 cycles;
|
||
|
|
uint8 rw;
|
||
|
|
uint16 slave_mask;
|
||
|
|
uint16 word_address;
|
||
|
|
T_EEPROM_STATE state;
|
||
|
|
T_EEPROM_TYPE type;
|
||
|
|
} T_EEPROM;
|
||
|
|
|
||
|
|
/* global variables */
|
||
|
|
extern T_EEPROM eeprom;
|
||
|
|
|
||
|
|
/* Function prototypes */
|
||
|
|
extern void EEPROM_Init();
|
||
|
|
extern void EEPROM_Write(unsigned int address, unsigned int value);
|
||
|
|
extern unsigned int EEPROM_Read(unsigned int address);
|
||
|
|
|