CAT24C01 datasheet(9/23 Pages) ONSEMI

9 / 23 page

CAT24C01, CAT24C02, CAT24C04, CAT24C08, CAT24C16

www.onsemi.com

READ OPERATIONS

Immediate Read

Upon receiving a Slave address with the R/W bit set to ‘1’,

the CAT24Cxx will interpret this as a request for data

residing at the current byte address in memory. The

CAT24Cxx will acknowledge the Slave address, will

immediately shift out the data residing at the current address,

and will then wait for the Master to respond. If the Master

does not acknowledge the data (NoACK) and then follows

up with a STOP condition (Figure 10), the CAT24Cxx

returns to Standby mode.

Selective Read

Selective Read operations allow the Master device to

select at random any memory location for a read operation.

The Master device first performs a ‘dummy’ write operation

by sending the START condition, slave address and byte

address of the location it wishes to read. After the

CAT24Cxx acknowledges the byte address, the Master

device resends the START condition and the slave address,

this time with the R/W bit set to one. The CAT24Cxx then

responds with its acknowledge and sends the requested data

byte. The Master device does not acknowledge the data

(NoACK) but will generate a STOP condition (Figure 11).

Sequential Read

If during a Read session, the Master acknowledges the 1st

data byte, then the CAT24Cxx will continue transmitting

data residing at subsequent locations until the Master

responds with a NoACK, followed by a STOP (Figure 12).

In contrast to Page Write, during Sequential Read the

address count will automatically increment to and then

wrap−around at end of memory (rather than end of page). In

the CAT24C01, the internal address count will not wrap

around at the end of the 128 byte memory space.

SCL

SDA

8th Bit

STOP

NO ACK

DATA OUT

SLAVE

ADDRESS

D ATA

BYTE

BUS ACTIVITY:

MASTER

SLAVE

Figure 10. Immediate Read Sequence and Timing

SLAVE

ADDRESS

D ATA

BYTE

ADDRESS

BYTE

ADDRESS

BUS ACTIVITY:

MASTER

SLAVE

Figure 11. Selective Read Sequence

SLAVE

ADDRESS

D ATA

BYTE

D ATA

BYTE

n+1

D ATA

BYTE

n+2

D ATA

BYTE

n+x

BUS ACTIVITY:

MASTER

SLAVE

Figure 12. Sequential Read Sequence

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