AT24CS04/08 [DATASHEET]
Atmel-8766E-SEEPROM-AT24CS04-08-Datasheet_012015
10
8. Device Addressing
Standard EEPROM Access: The 4-Kbit and 8-Kbit EEPROM device requires an 8-bit device address word
following a Start condition to enable the chip for a read or write operation.
The device address word consists of a mandatory ‘1010’ (Ah) sequence for the first four most significant bits
as shown in Figure 8-1 below. This is common to all Serial EEPROM devices.
The 4K EEPROM only uses the A2 and A1 device address bits with the third bit being a memory page address
bit (P0). The two device address bits must compare to their corresponding hard-wired input pins. Pin 1 is a no
connect. The 8K EEPROM only uses the A2 device address bit with the next two bits being for memory page
addressing (P1, P0). The A2 must compare to its corresponding hard-wired A2 input pin. Pins 1 and 2 are not
connected.
The eighth bit of the device address is the read/write operation select bit. A read operation is initiated 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 zero. If a compare is not made, the chip will
return to a standby state.
Note: For the SOT23 package offering, the 4-Kbit EEPROM software A2 and A1 bits in the device address
word must be set to zero to properly communicate. The 8-Kbit EEPROM software A2 bit in the device
address word must be set to zero to properly communicate in the SOT23 package.
Serial Number Access: The AT24CS04 and AT24CS08 utilizes a separate memory block containing a factory
programmed 128-bit serial number. Access to this memory location is obtained by beginning the device address
word with a ‘1011’ (Bh) sequence.
The behavior of the next three bits remain the same as during a standard EEPROM addressing sequence.
These three bits must compare to their corresponding hard-wired input pins A2 and A1 (4-Kbit only) in order for
the part to acknowledge. The restrictions for these bits with a SOT23 package are the same when accessing the
serial number feature.
The eighth bit of the device address needs be set to a one to read the Serial Number. A zero in this bit position,
other than during a dummy write sequence to set the address pointer, will result in a unknown data read from
the part. Writing or altering the 128-bit serial number is not possible.
Further specific protocol is needed to read the serial number from of the device. See Section 10., “Read
Operations” on page 12 for more details on accessing the special feature.
Table 8-1. Device Address
Density Access Area Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
4-Kbit EEPROM 1 0 1 0 A2A1P0 R/W
Serial Number 1 0 1 1 A2A10 1
8-Kbit EEPROM 1 0 1 0 A2P1 P0 R/W
Serial Number 1 0 1 1 A2001
MSB LSB