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Interfacing Serial EEPROM 89C51, 89C52, 89s52 Microcontrollers

Interfacing 24C01, 24C02, 24C04, 24C08, 24C16, 24C32, 24C64, 24C65, 24C128, 24C256, 24C512 8051 Microcontroller Family Models :
Atmel, NXP, Philips, 8051, 8052, 89C51, 89C52, 89S51, 89s52, 89C1051, 89C1051, 89C2051, AT89C4051, AT89S8252,l AT89C1051, AT89C2051, AT89C4051, P89C51RB+, P89C51RC+, P89C51RD+, P89C51RB2Hxx, P89C51RC2Hxx, P89C51RD2Hxx, P89C660, P89C662, P89C664, P89C668, P89C669, P89C51RA2xx, P89C51RB2xx, P89C51RC2xx, P89C51RD2xx, P89C60X2, P89C61X2,P89LV51RB2, P89LV51RC2, P89LV51RD2, P89V51RB2, P89V51RC2, P89V51RD2, P89V660, P89V662, P89V664.
About Serial EEPROMs Overview And Tutorials
Serial EEPROMs use a synchronous interface - both the EEPROM and the chip that controls it use a common clock, and clock transitions signal when to send and read each bit. For example, a sending device may write each bit on the rising edge of the clock, and the receiving device reads the bit when it detects the clock’s falling edge. Although some other synchronous serial chips require minimum clock frequencies, the clock for serial EEPROMs can be as slow as needed, and the clock signal doesn’t have to be symmetrical.
Various Models of Serial EEPROMs
Serial EEPROMs are available in the following models. These are some basic models and variants used into embedded industries. 24C01, 24C02, 24C04, 24C08, 24C16 I2C Bus EEPROM 24C32, 24C64, 24C65, 24C128, 24C256, 24C512 I2C Bus EEPROM 24XX EEPROM 24C325 and 24C645 I2C Bus EEPROM SDE2516, SDE2526, SDA2546, SDA2586, SDA3546, SDA3586 EEPROM AT17C65, AT17C128, AT17C256, AT17C512, AT17C010 I²C Bus EEPROM Siemens SDE2506 EEPROM 93C06, 93C46, 93C56, 93C57, 93C66, 93C76, 93C86 Microwire EEPROM 93C13, 93C06, 93C14, 93C46 Microwire EEPROM 25010, 25020, 25040 SPI EEPROM 25080, 25160, 25320, 25640, 25128, 25256 Big SPI EEPROM 25642 and 95640 Big SPI EEPROM
 I2C Tutorials Of Serial EEPROM
Serial I2C (Inter-Integrated Circuit Bus) is the final interface type. This one originated with Philips/Signetics, whose 8XC528 (8051 family) is an example of a microcontroller with an I2C interface built-in. The I2C interface requires just two signal lines, plus a common ground. Serial Data/Address (SDA) is a bidirectional line that requires open-collector or open-drain outputs. Serial Clock (SCL) is the clock. Instead of a chip-select line, the master sends a slave address on SDA. Figure 4 shows the timing for I2C transfers.

An I2C bus can have up to about 40 devices, with the limit determined by a maximum bus capicitance of 400 pF. Each device on the bus can have an address of up to 7 bits.
The open-collector/open-drain interface means that any logic-low output will pull SDA low. A device releases the SDA line by writing 1 to its output. Unlike Microwire and SPI, which are edge-sensitive, I2C is level-sensitive. Data and address bits on SDA may change only while SCL is low, and the receiving device reads bits after SCL goes high. There are two occasions when SDA changes state while SCL is high. A Start condition signals the beginning of an operation, and occurs when the master brings SDA low with SCL high. A Stop condition signals the end of an operation, and occurs when SDA goes high with SCL high.
 Interfacing/Connecting Serial EEPROM 8051 Microcontroller
Serial I2C (Inter-Integrated Circuit Bus) is the final interface type. This one originated with Philips.
Many designers today are implementing embedded systems that require low cost non-volatile memory. Microchip has addressed this need with a full line of serial EEPROMs, in a variety of memory configurations, using the industry-standard 2- or 3-wire communication protocols. 
Of the two wire serial EEPROMs from ATMEL, 24C02 is one of them and comes in different packages. No matter what the package type, following are the pins of 24C02 IC.
 Pin Description
A0-A2: Pins 1-3 are the address pins. Since multiple 24C02 and other similar devices can be connected to a system, they require addressing. These devices are hard wire addressed i.e. the address pins are permanently grounded and/or connected to Vcc. It is notable that in other two-wire serial EEPROMs from Atmel, all the address pins may not be used. In this circuit all address pins are grounded, so the device will have an address 000. WP: Pin7 is the Write Protect pin. When it is kept low (ground), normal read and write operations are allowed. When it is given a high, 24C02 is protected from any write operation. In the circuit WP pin has been grounded to allow write operation. Vcc: A 5V DC supply is required to power the AT24C02. This is same as the power supply of the microcontroller. So a separate supply to power 24C02 is not required. 
GND: Pin4 is Ground pin (0V) supply.
SDA: Pin5 is serial data pin. The data and control bits are read and write serially from this bidirectional pin.
SCL: Pin6 is serial clock pin. A clock signal is required every time a bit is transferred to or from the SDA pin. A positive edge clock, i.e., a low to high, transfers data to the EEPROM and a negative edge trigger, i.e., a high to low, carries data from the EEPROM. In the circuit SDA and SCL are connected to bits 0 and 1 of port P1, respectively.