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X24C08
1
Xicor, 1991 Patents Pending
Characteristics subject to change without notice
Serial E
2
PROM
Preliminary Information
TYPICAL FEATURES
2.7V to 5.5V Power Supply
Low Power CMOS
--Active Read Current Less Than 1 mA
--Active Write Current Less Than 3 mA
--Standby Current Less Than 50
A
Internally Organized 1024 x 8
2 Wire Serial Interface
--Bidirectional Data Transfer Protocol
Sixteen Byte Page Write Mode
--Minimizes Total Write Time Per Byte
Self Timed Write Cycle
--Typical Write Cycle Time of 5 ms
High Reliability
--Endurance: 100,000 Cycles
--Data Retention: 100 Years
8 Pin Mini-DlP, 8 Pin SOIC and 14 Pin
SOIC Packages
DESCRIPTION
The X24C08 is a CMOS 8,192 bit serial E
2
PROM,
internally organized 1024 x 8. The X24C08 features a
serial interface and software protocol allowing operation
on a simple two wire bus.
The X24C08 is fabricated with Xicor's advanced CMOS
Textured Poly Floating Gate Technology.
The X24C08 utilizes Xicor's proprietary Direct WriteTM
cell providing a minimum endurance of 100,000 cycles
and a minimum data retention of 100 years.
8K
X24C08
1024 x 8 Bit
FUNCTIONAL DIAGRAM
3842 FHD F01
START
STOP
LOGIC
CONTROL
LOGIC
SLAVE ADDRESS
REGISTER
+COMPARATOR
H.V. GENERATION
TIMING
& CONTROL
WORD
ADDRESS
COUNTER
XDEC
YDEC
DOUT
ACK
E
2
PROM
64 X 128
DATA REGISTER
START CYCLE
(8) VCC
R/W
PIN
(4) VSS
(5) SDA
(6) SCL
(3) A2
(2) A1
(1) A0
DOUT
LOAD
INC
CK
8
(7) TEST
3842-1
X24C08
2
PIN DESCRIPTIONS
Serial Clock (SCL)
The SCL input is used to clock all data into and out of the
device.
Serial Data (SDA)
SDA is a bidirectional pin used to transfer data into and
out of the device. It is an open drain output and may be
wire-ORed with any number of open drain or open
collector outputs.
An open drain output requires the use of a pull-up
resistor. For selecting typical values, refer to the Pull-Up
Resistor selection graph at the end of this data sheet.
Address (A
0
, A
1
)
A
0
and A
1
are unused by the X24C08; however, they
must be tied to V
SS
to insure proper device operation.
Address (A
2
)
The A
2
input is used to set the appropriate bit of the
seven bit slave address. This input can be used static or
actively driven. If used statically, it must be tied to V
SS
or
V
CC
as appropriate. If actively driven, it must be driven
to V
SS
or to V
CC
.
PIN CONFIGURATION
SOIC
DIP/SOIC
3842 FHD F03
PIN NAMES
Symbol
Description
A
0
A
2
Address Inputs
SDA
Serial Data
SCL
Serial Clock
TEST
Hold at V
SS
V
SS
Ground
V
CC
Supply Voltage
NC
No Connect
3842 PGM T01
NC
A0
A1
NC
A2
VSS
NC
1
2
3
4
5
6
7
14
13
12
11
10
9
8
NC
VCC
TEST
NC
SCL
SDA
NC
X24C08
VCC
TEST
SCL
SDA
A0
A1
A2
VSS
1
2
3
4
8
7
6
5
X24C08
3842 FHD F02
X24C08
3
DEVICE OPERATION
The X24C08 supports a bidirectional bus oriented pro-
tocol. The protocol defines any device that sends data
onto the bus as a transmitter, and the receiving device
as the receiver. The device controlling the transfer is a
master and the device being controlled is the slave. The
master will always initiate data transfers, and provide
the clock for both transmit and receive operations.
Therefore, the X24C08 will be considered a slave in all
applications.
Clock and Data Conventions
Data states on the SDA line can change only during SCL
LOW. SDA state changes during SCL HIGH are re-
served for indicating start and stop conditions. Refer to
Figures 1 and 2.
Start Condition
All commands are preceded by the start condition,
which is a HIGH to LOW transition of SDA when SCL is
HIGH. The X24C08 continuously monitors the SDA and
SCL lines for the start condition and will not respond to
any command until this condition has been met.
Stop Condition
All communications must be terminated by a stop con-
dition, which is a LOW to HIGH transition of SDA when
SCL is HIGH. The stop condition is also used by the
X24C08 to place the device into the standby power
mode after a read sequence. A stop condition can only
be issued after the transmitting device has released the
bus.
Figure 1. Data Validity
SCL
SDA
DATA STABLE
DATA
CHANGE
3842 FHD F06
Figure 2. Definition of Start and Stop
SCL
SDA
START BIT
STOP BIT
3842 FHD F07
X24C08
4
Acknowledge
Acknowledge is a software convention used to indicate
successful data transfers. The transmitting device will
release the bus after transmitting eight bits. During the
ninth clock cycle the receiver will pull the SDA line LOW
to acknowledge that it received the eight bits of data.
Refer to Figure 3.
The X24C08 will respond with an acknowledge after
recognition of a start condition and its slave address. If
both the device and a write operation have been se-
lected, the X24C08 will respond with an acknowledge
after the receipt of each subsequent eight bit word.
In the read mode the X24C08 will transmit eight bits of
data, release the SDA line and monitor the line for an
acknowledge. If an acknowledge is detected and no
stop condition is generated by the master, the X24C08
will continue to transmit data. If an acknowledge is not
detected, the X24C08 will terminate further data trans-
missions. The master must then issue a stop condition
to return the X24C08 to the standby power mode and
place the device into a known state.
Figure 3. Acknowledge Response From Receiver
SCL FROM
MASTER
DATA
OUTPUT
FROM
TRANSMITTER
1
8
9
DATA
OUTPUT
FROM
RECEIVER
START
ACKNOWLEDGE
3842 FHD F08
X24C08
5
The next bit addresses a particular device. A system
could have up to two X24C08 devices on the bus (see
Figure 10). The two addresses are defined by the state
of the A2 input.
The next two bits of the slave address field are an
extension of the array's address and are concatenated
with the eight bits of address in the word address field,
providing direct access to the whole 1024 x 8 array.
DEVICE ADDRESSING
Following a start condition the master must output the
address of the slave it is accessing. The most significant
four bits of the slave address are the device type
identifier (see Figure 4). For the X24C08 this is fixed as
1010[B].
Figure 4. Slave Address
The last bit of the slave address defines the operation to
be performed. When set to one a read operation is
selected, when set to zero a write operation is selected.
Following the start condition, the X24C08 monitors the
SDA bus comparing the slave address being transmit-
ted with its slave address (device type and state of A
2
input.) Upon a correct compare the X24C08 outputs an
acknowledge on the SDA line. Depending on the state
of the R/W bit, the X24C08 will execute a read or write
operation.
WRITE OPERATIONS
Byte Write
For a write operation, the X24C08 requires a second
address field. This address field is the word address,
comprised of eight bits, providing access to any one of
1024 words in the array. Upon receipt of the word
address the X24C08 responds with an acknowledge,
and awaits the next eight bits of data, again responding
with an acknowledge. The master then terminates the
transfer by generating a stop condition, at which time the
X24C08 begins the internal write cycle to the nonvolatile
memory. While the internal write cycle is in progress the
X24C08 inputs are disabled, and the device will not
respond to any requests from the master. Refer to
Figure 5 for the address, acknowledge and data transfer
sequence.
3842 FHD F09
Figure 5. Byte Write
BUS ACTIVITY:
MASTER
SDA LINE
BUS ACTIVITY:
X24C08
S
T
A
R
T
SLAVE
ADDRESS
S
S
T
O
P
P
A
C
K
A
C
K
A
C
K
WORD
ADDRESS
DATA
3842 FHD F10
1
0
A2
A1
A0
R/W
DEVICE TYPE
IDENTIFIER
DEVICE
ADDRESS
1
0
HIGH
ORDER
WORD
ADDRESS