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AT24CS32 [DATASHEET]

Atmel-8869B-SEEPROM-AT24CS32-Datasheet_012014

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 (see Figure 10-3).

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

/

W

A

C

K

A

C

K

A

C

K

A

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K

N

O

A

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K

SDA LINE

R

E

A

D

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T

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P

Device

Address

Data (n + x)

Data (n + 2)

Data (n + 1)

Data (n)