6

X24C04

Page Write

The X24C04 is capable of a sixteen byte page write

operation. It is initiated in the same manner as the byte

write operation, but instead of terminating the write cycle after

the first data word is transferred, the master can

transmit up to fifteen more words. After the receipt of each

word, the X24C04 will respond with an acknowledge.

After the receipt of each word, the four low order address bits

are internally incremented by one. The high order five

bits of the address remain constant. If the master should

transmit more than sixteen words prior to generating the

stop condition, the address counter will “roll over” and the

previously written data will be overwritten. As with the byte

write operation, all inputs are disabled until completion of the

internal write cycle. Refer to Figure 6 for the address,

acknowledge and data transfer sequence.

Acknowledge Polling

The disabling of the inputs can be used to take advan- tage

of the typical 5 ms write cycle time. Once the stop

condition is issued to indicate the end of the host’s write

operation the X24C04 initiates the internal write cycle.

ACK polling can be initiated immediately. This involves

issuing the start condition followed by the slave address

for a write operation. If the X24C04 is still busy with the write

operation no ACK will be returned. If the X24C04

has completed the write operation an ACK will be

returned and the host can then proceed with the next

read or write operation. Refer to Flow 1.

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 is set to a one. There are three basic read

operations: current address read, random read and

sequential read.

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

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

operation, 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.

Figure 6. Page Write

BUS ACTIVITY:

MASTER

SDA LINE

BUS ACTIVITY:

X24C04

S

T

A

R

T

SLAVE

ADDRESS

S

S

T

O

P

P

A

C

K

A

C

K

A

C

K

A

C

K

A

C

K

WORD

ADDRESS (n)

DATA n

DATA n+1

DATA n+15

NOTE: In this example n = xxxx 000 (B); x = 1 or 0

3839 FHD F11

Flow 1. ACK Polling Sequence

WRITE OPERATION

COMPLETED

ENTER ACK POLLING

ISSUE

START

ISSUE SLAVE

ADDRESS AND R/W = 0

ACK

RETURNED?

NEXT

OPERATION

A WRITE?

ISSUE BYTE

ADDRESS

PROCEED

ISSUE STOP

NO

YES

YES

PROCEED

ISSUE STOP

NO

3839 FHD F12