24LC01B/02B Modules
4.0
4.1
BUS CHARACTERISTICS
Slave Address
5.0
5.1
WRITE OPERATION
Byte Write
After generating a START condition, the bus master
transmits the slave address consisting of a 4-bit device
code (1010) for the 24LC01B/02B, 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 24LC01B/02B
The 24LC01B/02B monitors the bus for its correspond-
ing slave address all the time. It generates an acknowl-
edge bit if the slave address was true, and it is not in a
programming mode.
Operation
Read
Write
Control
Code
1010
1010
Chip
Select
XXX
XXX
R/W
1
0
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 transmitted
by the master is the word address and will be written
into the address pointer of the 24LC01B/02B. After
receiving another acknowledge signal from the
24LC01B/02B, the master device will transmit the data
word to be written into the addressed memory location.
The 24LC01B/02B acknowledges again and the master
generates a stop condition. This initiates the internal
write cycle, and during this time the 24LC01B/02B will
not generate acknowledge signals (Figure 5-1).
5.2
Page Write
FIGURE 4-1:
START
CONTROL BYTE
ALLOCATION
READ/WRITE
SLAVE ADDRESS
R/W
A
1
0
1
0
X
X
X
X = Don’t care
The write control byte, word address, and the first data
byte are transmitted to the 24LC01B/02B 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 24LC01B/02B, which are temporarily stored in the
on-chip page buffer and will be written into the memory
after the master has transmitted a stop condition. 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 con-
stant. 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 inter-
nal write cycle will begin (Figure 5-2).
FIGURE 5-1:
BUS ACTIVITY
MASTER
BYTE WRITE
S
T
A
R
T
CONTROL
BYTE
WORD
ADDRESS
DATA
S
T
O
P
SDA LINE
S
A
C
K
A
C
K
A
C
K
P
BUS ACTIVITY
FIGURE 5-2:
PAGE WRITE
S
T
A
R
T
CONTROL
BYTE
WORD
ADDRESS (n)
DATA n
DATAn + 1
DATAn + 7
S
T
O
P
BUS ACTIVITY
MASTER
SDA LINE
S
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
P
BUS ACTIVITY
©
1997 Microchip Technology Inc.
DS21222A-page 5
MICROCHIP [ MICROCHIP TECHNOLOGY ]
