24C32
4.0
4.1
WRITE OPERATION
Split Endurance
4.3
Page Write
The 24C32 is organized as a continuous 32K block of
memory. However, the first 4K, starting at address 000,
is rated at 10,000,000 E/W cycles guaranteed. The
remainder of the array, 28K bits, is rated at 100K E/W
cycles guaranteed. This feature is helpful in applica-
tions in which some data change frequently, while a
majority of the data change infrequently. One example
would be a cellular telephone in which last-number
redial and microcontroller scratch pad require a high-
endurance block, while speed dials and lookup tables
change infrequently and so require only a standard
endurance rating.
4.2
Byte Write
Following the start condition from the master, the con-
trol code (four bits), the device select (three bits), and
the R/W bit which is a logic low are clocked 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 acknowl-
edge bit during the ninth clock cycle. Therefore the next
byte transmitted by the master is the high-order byte of
the word address and will be written into the address
pointer of the 24C32. The next byte is the least signifi-
cant address byte. After receiving another acknowl-
edge signal from the 24C32 the master device will
transmit the data word to be written into the addressed
memory location. The 24C32 acknowledges again and
the master generates a stop condition. This initiates the
internal write cycle, and during this time the 24C32 will
not generate acknowledge signals (Figure 4-1).
The write control byte, word address and the first data
byte are transmitted to the 24C32 in the same way as
in a byte write. But instead of generating a stop condi-
tion, the master transmits up to eight pages of eight
data bytes each (64 bytes total) which are temporarily
stored in the on-chip page cache of the 24C32. They
will be written from cache into the EEPROM array after
the master has transmitted a stop condition. After the
receipt of each word, the six lower order address
pointer bits are internally incremented by one. The
higher order seven bits of the word address remain con-
stant. If the master should transmit more than eight
bytes prior to generating the stop condition (writing
across a page boundary), the address counter (lower
three bits) will roll over and the pointer will be incre-
mented to point to the next line in the cache. This can
continue to occur up to eight times or until the cache is
full, at which time a stop condition should be generated
by the master. If a stop condition is not received, the
cache pointer will roll over to the first line (byte 0) of the
cache, and any further data received will overwrite pre-
viously captured data. The stop condition can be sent
at any time during the transfer. As with the byte write
operation, once a stop condition is received, an internal
write cycle will begin. The 64-byte cache will continue
to capture data until a stop condition occurs or the oper-
ation is aborted (Figure 4-2).
FIGURE 4-1:
BYTE WRITE
S
t
o
p
S
t
Bus Activity: a
Master
r
t
SDA Line
Bus Activity
Control
Byte
Word
Address (1)
0000
A
C
K
A
C
K
Word
Address (0)
Data
A
C
K
A
C
K
FIGURE 4-2:
BUS
ACTIVITY
MASTER
SDA LINE
S
T
A
R
T
PAGE WRITE (FOR CACHE WRITE, SEE FIGURE 6-3)
CONTROL
BYTE
WORD
ADDRESS (1)
WORD
ADDRESS (0)
S
T
O
P
DATA n
DATA n + 7
0 0 0 0
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
BUS
ACTIVITY
DS21061F-page 6
©
1996 Microchip Technology Inc.
MICROCHIP [ MICROCHIP TECHNOLOGY ]
