CAT24AA16

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7

READ OPERATIONS

Immediate Read

To read data from memory, the Master creates a START

condition on the bus and then broadcasts a Slave address

with the R/W bit set to ‘1’. The Slave responds with ACK

and starts shifting out data residing at the current address.

After receiving the data, the Master responds with NoACK

and terminates the session by creating a STOP condition on

the bus (Figure 10). The Slave then returns to Standby mode.

Selective Read

To read data residing at a specific address, the selected

address must first be loaded into the internal address register.

This is done by starting a Byte Write sequence, whereby the

Master creates a START condition, then broadcasts a Slave

address with the R/W bit set to ‘0’ and then sends an address

byte to the Slave. Rather than completing the Byte Write

sequence by sending data, the Master then creates a START

condition and broadcasts a Slave address with the R/W bit

set to ‘1’. The Slave responds with ACK after every byte sent

by the Master and then sends out data residing at the selected

address. After receiving the data, the Master responds with

NoACK and then terminates the session by creating a STOP

condition on the bus (Figure 11).

Sequential Read

If, after receiving data sent by the Slave, the Master

responds with ACK, then the Slave will continue

transmitting until the Master responds with NoACK

followed by STOP (Figure 12). During Sequential Read the

internal byte address is automatically incremented up to the

end of memory, where it then wraps around to the beginning

of memory.

SCL

SDA

STOP

NO ACK

DATA OUT

89

SLAVE

ADDRESS

S

A

C

K

DATA

BYTE

N

O

A

C

K

S

T

O

P

P

S

T

A

R

T

BUS ACTIVITY:

MASTER

SLAVE

Figure 10. Immediate Read Sequence and Timing

SLAVE

S

A

C

K

N

O

A

C

K

P

S

T

A

R

T

S

SLAVE

ADDRESS

DATA

BYTE

ADDRESS

BYTE

ADDRESS

BUS ACTIVITY:

MASTER

SLAVE

S

T

A

R

T

S

T

O

P

Figure 11. Selective Read Sequence

A

C

K

A

C

K

A

C

K

A

C

K

A

C

K

S

T

O

P

N

O

A

C

K

A

C

K

P

SLAVE

ADDRESS

DATA

BYTE

n

DATA

BYTE

n+1

DATA

BYTE

n+2

DATA

BYTE

n+x

BUS ACTIVITY:

MASTER

SLAVE

Figure 12. Sequential Read Sequence