24AA01H Datasheet, PDF (10/30 Pages) Microchip Technology – 1K I2C™ Serial EEPROM with Half-Array Write-Protect

24AA01H/24LC01BH
8.0 READ OPERATION
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 ‘1’. There are three basic types
of read operations: current address read, random read
and sequential read.
8.1 Current Address Read
The 24XX01H contains an address counter that
maintains the address of the last word accessed,
internally incremented by ‘1’. Therefore, if the previous
access (either a read or write operation) was to
address n, the next current address read operation
would access data from address n + 1. Upon receipt of
the slave address with R/W bit set to ‘1’, the 24XX01H
issues an acknowledge and transmits the 8-bit data
word. The master will not acknowledge the transfer, but
does generate a Stop condition and the 24XX01H
discontinues transmission (Figure 8-1).
8.2 Random Read
Random read operations allow the master to access
any memory location in a random manner. To perform
this type of read operation, the word address must first
be set. This is accomplished by sending the word
address to the 24XX01H as part of a write operation.
Once the word address is sent, the master generates
a Start condition following the acknowledge. This
terminates the write operation, but not before the inter-
nal Address Pointer is set. The master then issues the
control byte again, but with the R/W bit set to a ‘1’. The
24XX01H will then issue an acknowledge and
transmits the 8-bit data word. The master will not
acknowledge the transfer, but does generate a Stop
condition and the 24XX01H discontinues transmission
(Figure 8-2).
8.3 Sequential Read
Sequential reads are initiated in the same way as a
random read, except that once the 24XX01H transmits
the first data byte, the master issues an acknowledge
(as opposed to a Stop condition in a random read). This
directs the 24XX01H to transmit the next sequentially
addressed 8-bit word (Figure 8-3).
To provide sequential reads the 24XX01H contains an
internal Address Pointer which is incremented by one
at the completion of each operation. This Address
Pointer allows the entire memory contents to be serially
read during one operation.
8.4 Noise Protection
The 24XX01H employs a VCC threshold detector circuit
which disables the internal erase/write logic if the VCC
is below 1.5V at nominal conditions.
The SCL and SDA inputs have Schmitt Trigger and
filter circuits which suppress noise spikes to assure
proper device operation even on a noisy bus.
FIGURE 8-1:
CURRENT ADDRESS READ
S
Bus Activity
T
Master
A
R
T
Control
Byte
S
Data (n)
T
O
P
SDA Line
Bus Activity
x = “don’t care”
S1 0 10xxx1
A
Block
C
K
Select
Bits
P
N
o
A
C
K
DS22104A-page 10
© 2008 Microchip Technology Inc.