24LC00 MicrochipTechnology, 24LC00 Datasheet - Page 7

• Manufacturer Part Number: 24LC00
• Description: 128BitI2CBusSerialEEPROM
• Manufacturer: MicrochipTechnology

8.0
Read operations are initiated in the same way as write
operations with the exception that the R/W bit of the
slave address is set to one. There are three basic types
of read operations: current address read, random read,
and sequential read.
8.1
The 24xx00 contains an address counter that maintains
the address of the last word accessed, internally incre-
mented by one. Therefore, if the previous read access
was to address n, the next current address read opera-
tion would access data from address n + 1. Upon
receipt of the slave address with the R/W bit set to one,
the device issues an acknowledge and transmits the
eight bit data word. The master will not acknowledge
the transfer but does generate a stop condition and the
device discontinues transmission (Figure 8-1).
8.2
Random read operations allow the master to access
any memory location in a random manner. To perform
this type of read operation, first the word address must
be set. This is done by sending the word address to the
FIGURE 8-1:
FIGURE 8-2:
FIGURE 8-3:
1996 Microchip Technology Inc.
BUS ACTIVITY
MASTER
SDA LINE
BUS ACTIVITY
READ OPERATIONS
Current Address Read
Random Read
X = Don’t Care Bit
BUS ACTIVITY
MASTER
SDA LINE
BUS ACTIVITY
CURRENT ADDRESS READ
RANDOM READ
SEQUENTIAL READ
CONTROL
BYTE
S
T
A
R
T
S 1
A
C
K
0
CONTROL
BUS ACTIVITY
MASTER
SDA LINE
BUS ACTIVITY
1
X = Don’t Care Bit
BYTE
0 X X X 0
DATA n
A
C
K
X X X X
A
C
K
ADDRESS (n)
Preliminary
S
T
A
R
T
S
WORD
DATA n + 1
1
0
CONTROL
1
BYTE
0 X X X 1
device as part of a write operation. After the word
address is sent, the master generates a start condition
following the acknowledge. This terminates the write
operation, but not before the internal address pointer is
set. Then the master issues the control byte again but
with the R/W bit set to a one. The 24xx00 will then issue
an acknowledge and transmits the eight bit data word.
The master will not acknowledge the transfer but does
generate a stop condition and the device discontinues
transmission (Figure 8-2). After this command, the
internal address counter will point to the address loca-
tion following the one that was just read.
8.3
Sequential reads are initiated in the same way as a ran-
dom read except that after the device transmits the first
data byte, the master issues an acknowledge as
opposed to a stop condition in a random read. This
directs the device to transmit the next sequentially
addressed 8-bit word (Figure 8-3).
To provide sequential reads the 24xx00 contains an
internal address pointer which is incremented by one at
the completion of each read operation. This address
pointer allows the entire memory contents to be serially
read during one operation.
A
C
K
S
T
A
R
T
S 1
A
C
K
A
C
K
0
CONTROL
DATA n + 2
1
Sequential Read
BYTE
0 X X X 1
DATA
A
C
K
A
C
K
N
O
A
C
K
S
T
O
P
P
DATA (n)
DATA n + X
24xx00
N
O
C
A
K
DS21178A-page 7
S
T
O
P
P
N
O
A
C
K
S
T
O
P
P