Datasheet

Atmel AT30TSE002B [DATASHEET]

8711G–SEEPR–5/12

13. EEPROM Read Operations

Read operations are initiated the same way as write operations with the exception that the read/write select bit in the

device address word is set to one. There are three read operations: current address read, random address read, and

sequential read.

Current Address Read: The internal data word address counter maintains the last address accessed during the last

read or write operation, incremented by one. This address stays valid between operations as long as the chip power is

maintained. The address “roll over” during read is from the last byte of the last memory page to the first byte of the first

page.

Once the device address with the read/write select bit set to one is clocked in and acknowledged by the EEPROM, the

current address data word is serially clocked out. To end the command, the microcontroller does not respond with an

input zero but does generate a following stop condition (see Figure 13-4).

Random Read: A random read requires a dummy byte write sequence to load in the data word address. Once the

device address word and data word address are clocked in and acknowledged by the EEPROM, the microcontroller must

generate another start condition. The microcontroller now initiates a current address read by sending a device address

with the read/write select bit high. The EEPROM acknowledges the device address and serially clocks out the data word.

To end the command, the microcontroller does not respond with a zero but does generate a following stop condition (see

Figure 13-5).

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 ACK. As long as the EEPROM receives an ACK, 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 13-6).

Permanent Write Protect Register (PSWP) Status: To find out if the register has been programmed, the same

procedure is used as to program the register except that the R/W bit is set to one. If the device sends an acknowledge,

then the permanent write protect register has not been programmed; otherwise, it has been programmed and the device

is permanently write protected at the first half of the array.

Table 13-1. PSWP Status

Reversible Write Protect Register (RSWP) Status: To find out if the register has been programmed, the same

procedure is used as to program the register except that the R/W bit is set to one. If the device sends an acknowledge,

then the reversible write protect register has not been programmed; otherwise, it has been programmed and the device is

write protected (reversible) at the first half of the array.

Figure 13-1. EEPROM Device Address

Command

Pin Preamble R/W

A2 A1 A0 B7 B6 B5 B4 B3 B2 B1 B0

Read PSWP A2 A1 A0 0 1 1 0 A2 A1 A0 1

MSB LSB

1 0 1 0 A2 A1 A0 R/W