24LC09_04 Datasheet, PDF (7/18 Pages) Microchip Technology – 8K 2.5V ACR SERIAL EEPROM

24LC09
5.0 WRITE OPERATION
5.1 Byte Write
Following the start condition from the master, the
device code (4 bits), the block address (3 bits), and the
R/W bit which is a logic low is placed onto the bus by
the master transmitter. This indicates to the addressed
slave receiver that a byte with a word address will fol-
low after it has generated an acknowledge bit during
the ninth clock cycle. Therefore, the next byte transmit-
ted by the master is the word address and will be writ-
ten into the address pointer of the 24LC09. After
receiving another acknowledge signal from the 24LC09
the master device will transmit the data word to be writ-
ten into the addressed memory location. The 24LC09
acknowledges again and the master generates a stop
condition. This initiates the internal write cycle, and dur-
ing this time the 24LC09 will not generate acknowledge
signals (Figure 5-1).
5.2 Page Write
The write control byte, word address and the first data
byte are transmitted to the 24LC09 in the same way as
in a byte write. But instead of generating a stop condi-
tion the master transmits up to 16 data bytes to the
24LC09 which are temporarily stored in the on-chip
page buffer and will be written into the memory after the
FIGURE 5-1:
BUS ACTIVITY
MASTER
BYTE WRITE
S
T
A
R
CONTROL
BYTE
T
SDA LINE
S
A
BUS ACTIVITY
C
K
master has transmitted a stop condition. After the
receipt of each word, the four lower order address
pointer bits are internally incremented by one. The
higher order seven bits of the word address remains
constant. If the master should transmit more than 16
words prior to generating the stop condition, the
address counter will roll over and the previously
received data will be overwritten. As with the byte write
operation, once the stop condition is received an inter-
nal write cycle will begin (Figure 5-2).
Note:
Page write operations are limited to writing
bytes within a single physical page, regard-
less of the number of bytes actually being
written. Physical page boundaries start at
addresses that are integer multiples of the
page buffer size (or ‘page size’) and end at
addresses that are integer multiples of
[page size - 1]. If a page write command
attempts to write across a physical page
boundary, the result is that the data wraps
around to the beginning of the current page
(overwriting data previously stored there),
instead of being written to the next page as
might be expected. It is therefore neces-
sary for the application software to prevent
page write operations that would attempt to
cross a page boundary.
WORD
ADDRESS
A
C
K
DATA
S
T
O
P
P
A
C
K
FIGURE 5-2:
BUS ACTIVITY
MASTER
SDA LINE
BUS ACTIVITY
PAGE WRITE
S
T
A
R
CONTROL
BYTE
T
S
WORD
ADDRESS (n)
A
A
C
C
K
K
DATA n
DATA n + 1
A
C
K
S
DATA n + 15
T
O
P
P
A
A
C
C
K
K
 2004 Microchip Technology Inc.
DS21675B-page 7