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AT24CS64 [DATASHEET]

Atmel-8870B-SEEPROM-AT24CS64-Datasheet_082014

Sequential Read: Sequential reads are initiated by either a current address read or a random address read.

After the microcontroller receives a data word, it responds with an acknowledge. As long as the EEPROM

receives an acknowledge, it will continue to increment the data word address and serially clock out sequential

data words. When the memory address limit is reached, the data word address will roll-over and the Sequential

Read will continue. The Sequential Read operation is terminated when the microcontroller does not respond

with a zero but does generate a following Stop condition.

Figure 10-3.

Sequential Read

Serial Number Read: Reading the serial number is similar to the sequential read sequence but requires use of

the device address seen in Table 8-1 on page 10, a dummy write, and the use of a specific word address.

Note: The entire 128-bit value must be read from the starting address of the serial number block to guarantee

a unique number.

Since the address pointer of the device is shared between the regular EEPROM array and the serial number

block, a dummy write sequence, as part of a Random Read or Sequential Read protocol, should be performed

to ensure the address pointer is set to zero. A Current Address Read of the serial number block is supported but

if the previous operation was to the EEPROM array, the address pointer will retain the last location accessed,

incremented by one. Reading the serial number from a location other than the first address of the block will not

result in a unique serial number.

Additionally, the word address contains a ‘10’ sequence in bit A11 and A10 of the word address, regardless of

the intended address as depicted in Table 8-2 on page 10. If a word address other than ‘10’ is used, then the

device will output undefined data.

Example:

If the application desires to read the first byte of the serial number, the word address input would

need to be 0800h.

When the end of the 128-bit serial number is reached (16 bytes of data), continued reading of the extended

memory region will result in an additional 16 bytes of 00h data. Upon reaching the end of the 32-byte extended

memory region, the data word address will roll-over back to the beginning of the 128-bit serial number. The

Serial Number Read operation is terminated when the microcontroller does not respond with a zero (ACK) and

instead issues a Stop condition (see Figure 10-4 on page 14).

R

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W

A

C

K

A

C

K

A

C

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A

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N

O

A

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SDA LINE

R

E

A

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Device

Address

Data (n + x)

Data (n + 2)

Data (n + 1)

Data (n)