Figure 6-6.
Output Acknowledge
SCL
1
8
9
DATA IN
DATA OUT
START
ACKNOWLEDGE
7. Device Addressing
The 128K EEPROM requires an 8-bit device address word following a start condition to enable
the chip for a read or write operation (see Figure 7-1 ). The device address word consists of a
mandatory “1”, “0” sequence for the first four most significant bits as shown. This is common to
all two-wire EEPROM devices.
Figure 7-1.
Device Address
1
0
1
0
A2
A1
A0
R/W
MSB
LSB
The next three bits are the A2, A1, A0 device address bits to allow as many as eight devices on
the same bus. These bits must compare to their corresponding hardwired input pins. The A2,
A1, and A0 pins use an internal proprietary circuit that biases them to a logic low condition if the
pins are allowed to float.
The eighth bit of the device address is the read/write operation select bit. A read operation is ini-
tiated if this bit is high, and a write operation is initiated if this bit is low.
Upon a compare of the device address, the EEPROM will output a “0”. If a compare is not made,
the device will return to a standby state.
DATA SECURITY: The AT24C128B has a hardware data protection scheme that allows the user
to write protect the whole memory when the WP pin is at V CC .
8
AT24C128B
5296A–SEEPR–1/08
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AT24C128C-CUM-T 制造商:Atmel Corporation 功能描述:
AT24C128C-MAHM-T 功能描述:电可擦除可编程只读存储器 SERIAL 电可擦除可编程只读存储器 128K (16K x 8) 2WIRE 1.7V RoHS:否 制造商:Atmel 存储容量:2 Kbit 组织:256 B x 8 数据保留:100 yr 最大时钟频率:1000 KHz 最大工作电流:6 uA 工作电源电压:1.7 V to 5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8