24C01SC/02SC
4.0
BUS CHARACTERISTICS
5.0
WRITE OPERATION
4.1
Slave Address
5.1
Byte Write
After generating a START condition, the bus master
transmits the slave address consisting of a 4-bit device
code (1010) for the 24C01SC/02SC, followed by three
don't care bits.
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 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 5-1).
The eighth bit of slave address determines if the master
device wants to read or write to the 24C01SC/02SC
(Figure 4-1).
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.
Control
Code
Chip
Select
Operation
R/W
Read
Write
1010
1010
XXX
XXX
1
0
5.2
Page Write
FIGURE 4-1: CONTROL BYTE
ALLOCATION
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 inter-
nal write cycle will begin (Figure 5-2).
START
READ/WRITE
R/W
X
A
SLAVE ADDRESS
1
0
1
0
X
X
X = Don’t care
FIGURE 5-1: BYTE WRITE
S
BUS ACTIVITY
MASTER
T
A
R
T
S
T
O
P
CONTROL
BYTE
WORD
ADDRESS
DATA
SDA LINE
S
P
A
C
K
A
C
K
A
C
K
BUS ACTIVITY
FIGURE 5-2: PAGE WRITE
S
BUS ACTIVITY
MASTER
T
S
T
O
P
CONTROL
BYTE
WORD
ADDRESS (n)
A
R
T
DATA n
DATAn + 1
DATAn + 7
SDA LINE
S
P
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
BUS ACTIVITY
1996 Microchip Technology Inc.
Preliminary
DS21170A-page 5
MICROCHIP [ MICROCHIP ]
