X9521

FN8207 Rev 2.00

Page 10 of 24

September 21, 2010

EEPROM Array Read Operations

Read operations are initiated in the same manner as write

operations with the exception that the R/W bit of the Slave

Address Byte is set to one. There are three basic read

operations: Current EEPROM Address Read, Random

EEPROM Read, and Sequential EEPROM Read.

Current EEPROM Address Read

Internally the device contains an address counter that

maintains the address of the last word read incremented by

one. Therefore, if the last read was to address n, the next

read operation would access data from address n+1. On

power-up, the address of the address counter is undefined,

requiring a read or write operation for initialization.

Upon receipt of the Slave Address Byte with the R/W bit set

to one, the device issues an ACKNOWLEDGE and then

transmits the eight bits of the Data Byte. The master termi-

nates the read operation when it does not respond with an

ACKNOWLEDGE during the ninth clock and then issues a

STOP condition (See Figure 14 for the address,

ACKNOWLEDGE, and data transfer sequence).

It should be noted that the ninth clock cycle of the read

operation is not a “don’t care.” To terminate a read opera-

tion, the master must either issue a STOP condition during

the ninth cycle or hold SDA HIGH during the ninth clock

cycle and then issue a STOP condition.

Another important point to note regarding the “Current

EEPROM Address Read” , is that this operation is not

available if the last executed operation was an access to a

DCP or the CONSTAT Register (i.e.: an operation using

the Device Type Identifier 1010111 or 1010010). Immedi-

ately after an operation to a DCP or CONSTAT Register is

performed, only a “Random EEPROM Read” is available.

Immediately following a “Random EEPROM Read” , a

“Current EEPROM Address Read” or “Sequential

EEPROM Read” is once again available (assuming that no

access to a DCP or CONSTAT Register occur in the

interim).

address

address

11

5 bytes

15

7 bytes

address

= 6

address pointer

ends here

Addr = 7

Figure 13. Example: Writing 12 bytes to a 16-byte page starting at location 11.

5 bytes

10

10

10

10

S

t

a

r

t

S

t

o

p

Slave

Address

Data

A

C

K

SDA Bus

Signals from

the Slave

Signals from

the Master

1

Figure 14. Current EEPROM Address Read Sequence

1 01 0 0 0 0