1,24C02 Profile
2Kbit 24C02 is a serial EEPROM memory chip, it can store 256 bytes of data. Operating voltage range of 1.8V to 6.0V, a low-power CMOS technology, since the timing of erase cycles, 1,000,000 program / erase cycles, the data can be stored for 100 years. 24C02 has a 16-byte page write buffer and a write protection. Chip communication through the I2C bus to read and write data, the clock frequency up communication 400KHz.
Model may be calculated by the storage capacity of memory IC chip is much like the back 02 24C02 are indicated 2Kbit may store data, converted to a byte storage is 2 * 1024/8 = 256byte; 24C04 behind there, such as 04 indicates that the data may be stored 4Kbit, converted to a byte storage capacity is 2 * 1024/8 = 512byte; this analogy to other types of storage space.
FIG 24C02 pin follows:
VCC and VSS is the chip power and ground, of the working voltage range: + 1.8V ~ + 6.0V.
A0, A1, A2 is the address selection pin IC.
WP is write-protected enable pin.
SCL is the I2C communication clock pin.
SDA is I2C communications data pins.
2,24C02 device address and write protection
When the host 24C02 I2C communication, a device needs to send address addressing, on the I2C bus, each unique address of the slave device is.
24C02 device address consists of two parts, the first part is fixed bit7 ~ bit4 is "1010", the second portion of bit3 ~ bit1 bits A2, A1, A0 composition. When the host to communicate with 24C02, in addition to the transmitting device you need to send the address to read and write data direction bit R / W, 24C02 the device address and R / W bits of a byte of data. As shown below:
The figure shows the device address byte with the R / W bit consisting of several memory IC. Can be seen from the figure, bit7 ~ bit4 bit fixed address memory IC is "1010"; bit3 ~ bit1 is determined by bits A2, A1, A0 pin level state, if the power supply is connected to Ax (high) , then Ax = 1, if Ax is a ground contact, then Ax = 0, i.e., the A2, A1, A0 may be combined into 8 device address, i.e. on the same I2C bus 8 can mount chips while 24C02 . Generally if the I2C bus is only a 24C02 chip, then, A2, A1, A0 pin to ground.
24C02 Since only 256 bytes of storage space, so only 8 bit (1 th byte) address bits can be addressed 24C02 complete storage, but can not completely address a larger memory capacity of the IC, such as the 24C04 memory capacity is 512 bytes, requires nine-bit address bits to complete addressing. Can be seen from the figure, the device address is not 24C04 parameters A0, was replaced a8, a8 is the address of the bit 9-bit 24C04, i.e. the A0 pin 24C04 was ineffective, it also resulted in the I2C bus can simultaneously mount four 24C04 chip. Other memory as 24C08,24C16 could be so on.
24C02 WP pin is write protection pin WP when the pin high, 24C02 read only operation, a write operation can not be performed. Only when the WP pin is left floating or tied low, 24C02 to write.