CMOS 2-WIRED SERIAL EEPROM

S-24C01A/02A/04A

12

Seiko Instruments Inc.

7.2 Random Read

Random read is a mode used when the data is read from arbitrary memory addresses.

To load a memory address into the address counter inside the EEPROM, first perform a dummy write

according to the following procedures:

When the EEPROM receives a 7-bit length device address and a 1-bit read/write instruction code "0,"

following the start condition signal, it outputs the acknowledgment signal.

Next, the EEPROM receives an 8-bit length word address and outputs the acknowledgment signal. Last,

the memory address is loaded into the address counter of the EEPROM.

the EEPROM receives the write data during byte or page writing. However, data reception is not

performed during dummy write.

The memory address is loaded into the memory address counter inside the EEPROM during dummy write.

After that, the master device can read the data starting from the arbitrary memory address by transmitting

a new start condition signal and performing the same operation as that in the "Current Read."

That is, when the EEPROM receives a 7-bit length device address and a 1-bit read/write instruction code

"1," following the start condition signal, it outputs the acknowledgment signal.

Next, 8-bit length data is output from the EEPROM, in synchronization with the SCL clock. The master

device does not output an acknowledgment signal and transmits the stop condition signal to finish reading.

S

T

A

R

T

1

0 1 0

W

R

I

T

E

S

T

O

P

DEVICE

ADDRESS

WORD ADDRESS (n)

R

/

W

M

S

B

SDA LINE

A2 A1 A0

W7W6W5W4W3W2W1W0

A

C

K

L

S

B

A

C

K

A

C

K

0

1

0 1 0 A2 A1 A0 1

D7 D6 D5 D4 D3 D2 D1 D0

DATA (n)

DUMMY WRITE

DEVICE

ADDRESS

R

E

A

D

NO ACK from

Master Device

ADR INC

S

T

A

R

T

W7 is optional in the S-24C01A.

A0 is P0 in the S-24C04A.

Figure 13 Random Read