24AA04 MicrochipTechnology, 24AA04 Datasheet - Page 6

• Manufacturer Part Number: 24AA04
• Description: 4K/8K1.8VI2CSerialEEPROMs
• Manufacturer: MicrochipTechnology

24AA04/08
5.0
Since the device will not acknowledge during a write
cycle, this can be used to determine when the cycle is
complete (this feature can be used to maximize bus
throughput). Once the stop condition for a write com-
mand has been issued from the master, the device ini-
tiates the internally timed write cycle. ACK polling can
be initiated immediately. This involves the master send-
ing a start condition followed by the control byte for a
write command (R/W = 0). If the device is still busy with
the write cycle, then no ACK will be returned. If the
cycle is complete, then the device will return the ACK
and the master can then proceed with the next read or
write command. See Figure 5-1 for flow diagram.
FIGURE 5-1:
6.0
The 24AA04/08 can be used as a serial ROM when the
WP pin is connected to V
ited and the entire memory will be write-protected.
DS21053E-page 6
ACKNOWLEDGE POLLING
WRITE PROTECTION
Initiate Write Cycle
Send Control Byte
Write Command
with R/W = 0
Acknowledge
Condition to
Send Stop
(ACK = 0)?
Did Device
Send Start
Operation
ACKNOWLEDGE POLLING
FLOW
Send
Next
CC
YES
. Programming will be inhib-
NO
7.0
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.
7.1
The 24AA04/08 contains an address counter that main-
tains the address of the last word accessed, internally
incremented by one. 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 one, the 24AA04/08 issues an
acknowledge and transmits the 8-bit data word. The
master will not acknowledge the transfer but does gen-
erate a stop condition and the 24AA04/08 discontinues
transmission (Figure 7-1).
7.2
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
24AA04/08 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 24AA04/08 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 24AA04/08 dis-
continues transmission (Figure 7-2).
7.3
Sequential reads are initiated in the same way as a ran-
dom read except that after the 24AA04/08 transmits the
first data byte, the master issues an acknowledge as
opposed to a stop condition in a random read. This
directs the 24AA04/08 to transmit the next sequentially
addressed 8-bit word (Figure 7-3).
To provide sequential reads the 24AA04/08 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.
7.4
The 24AA04/08 employs a V
cuit which disables the internal erase/write logic if the
V
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.
CC
is below 1.5 volts at nominal conditions.
READ OPERATION
Current Address Read
Random Read
Sequential Read
Noise Protection
1996 Microchip Technology Inc.
CC
threshold detector cir-