24C01SC_04 Datasheet, PDF (5/16 Pages) Microchip Technology – 1K/2K 5.0V I2C Serial EEPROMs for Smart Cards

3.6 Slave Address
After generating a Start condition, the bus master trans-
mits the slave address consisting of a 4-bit device code
(1010) for the 24C01SC/02SC, followed by three “don't
care” bits.
The eighth bit of slave address determines if the master
device wants to read or write to the 24C01SC/02SC
(Figure 3-2).
The 24C01SC/02SC monitors the bus for its corre-
sponding slave address all the time. It generates an
Acknowledge bit if the slave address was true, and it is
not in a programming mode.
Operation
Control
Code
Chip
Select
R/W
Read
1010
xxx
1
Write
1010
xxx
0
FIGURE 3-2:
Start
CONTROL BYTE
ALLOCATION
Read/Write
SLAVE ADDRESS
R/W A
1
0
10x
x
x
X = don’t care
24C01SC/24C02SC
4.0 WRITE OPERATION
4.1 Byte Write
Following the Start signal from the master, the device
code (4 bits), the “don't care” bits (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
follow 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
written into the address pointer of the 24C01SC/02SC.
After receiving another Acknowledge signal from the
24C01SC/02SC, the master device will transmit the
data word to be written into the addressed memory
location. The 24C01SC/02SC acknowledges again
and the master generates a Stop condition. This
initiates the internal write cycle, and during this time the
24C01SC/02SC will not generate Acknowledge signals
(Figure 4-1).
4.2 Page Write
The write control byte, word address, and the first data
byte are transmitted to the 24C01SC/02SC in the same
way as in a byte write. But instead of generating a Stop
condition, the master transmits up to eight data bytes to
the 24C01SC/02SC, which are temporarily stored in
the on-chip page buffer and will be written into the
memory after the master has transmitted a Stop condi-
tion. After the receipt of each word, the three lower
order address pointer bits are internally incremented by
one. The higher order five bits of the word address
remains constant. If the master should transmit more
than eight 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
internal write cycle will begin (Figure 4-2).
Note:
Page write operations are limited to writing
bytes within a single physical page,
regardless of the number of bytes actually
being written. Physical page boundaries
start at addresses that are integer multi-
ples 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 necessary for the
application software to prevent page write
operations that would attempt to cross a
page boundary.
 2004 Microchip Technology Inc.
DS21170E-page 5