Preliminary Information
PinX240427 No Connect
4K |
X24042 |
512 x 8 Bit |
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Serial E2PROM |
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TYPICAL FEATURES |
DESCRIPTION |
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•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 μA
•Internally Organized 512 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 and 8 Pin SOIC Packages
The X24042 is a CMOS 4,096 bit serial E2PROM, internally organized 512 x 8. The X24042 features a serial interface and software protocol allowing operation on a simple two wire bus.
The X24042 is fabricated with Xicor’s advanced CMOS Textured Poly Floating Gate Technology.
The X24042 utilizes Xicor’s proprietary Direct WriteTM cell providing a minimum endurance of 100,000 cycles and a minimum data retention of 100 years.
FUNCTIONAL DIAGRAM
(8) |
VCC |
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(4) |
VSS |
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START CYCLE |
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H.V. GENERATION |
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TIMING |
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& CONTROL |
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(5) SDA |
START |
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STOP |
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LOGIC |
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CONTROL |
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LOGIC |
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SLAVE ADDRESS |
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E2PROM |
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REGISTER |
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XDEC |
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(6) SCL |
LOAD |
INC |
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32 X 128 |
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+COMPARATOR |
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(3) A2 |
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WORD |
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(2) A1 |
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ADDRESS |
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COUNTER |
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(1) A0 |
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R/W |
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YDEC |
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8 |
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PIN |
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CK |
DOUT |
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DATA REGISTER |
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DOUT |
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ACK |
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3849 FHD F01
© Xicor, 1991 Patents Pending |
1 |
Characteristics subject to change without notice |
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3849-1 |
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X24042
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 (A0)
A0 is unused by the X24042, however, it must be tied to VSS to insure proper device operation.
Address (A1, A2)
The Address inputs are used to set the appropriate bits of the seven bit slave address. These inputs can be used static or actively driven. If used statically they must be tied to VSS or VCC as appropriate. If driven they must be driven to VSS or to VCC.
PIN CONFIGURATION
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DIP/SOIC |
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A0 |
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1 |
8 |
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VCC |
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A1 |
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2 |
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NC |
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A2 |
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X24042 |
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3 |
6 |
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SCL |
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VSS |
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4 |
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SDA |
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3849 FHD F02 |
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PIN NAMES |
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Symbol |
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Description |
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A0–A2 |
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Address Inputs |
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SDA |
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Serial Data |
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SCL |
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Serial Clock |
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NC |
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No Connect |
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VSS |
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Ground |
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VCC |
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Supply Voltage |
3849 PGM T01
2
X24042
DEVICE OPERATION
The X24042 supports a bidirectional bus oriented protocol. 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 X24042 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 reserved for indicating start and stop conditions. Refer to Figures 1 and 2.
Figure 1. Data Validity
Start Condition
All commands are preceded by the start condition, which is a HIGH to LOW transition of SDA when SCL is HIGH. The X24042 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 condition, which is a LOW to HIGH transition of SDA when SCL is HIGH. The stop condition is also used by the X24042 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.
SCL
SDA
DATA STABLE DATA CHANGE
3849 FHD F06
Figure 2. Definition of Start and Stop
SCL
SDA
START BIT |
STOP BIT |
3849 FHD F07
3
X24042
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 X24042 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 selected, the X24042 will respond with an acknowledge
Figure 3. Acknowledge Response From Receiver
after the receipt of each subsequent eight bit word.
In the read mode the X24042 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 X24042 will continue to transmit data. If an acknowledge is not detected, the X24042 will terminate further data transmissions. The master must then issue a stop condition to return the X24042 to the standby power mode and place the device into a known state.
SCL FROM |
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MASTER |
1 |
8 |
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DATA
OUTPUT
FROM
TRANSMITTER
DATA
OUTPUT
FROM
RECEIVER
START |
ACKNOWLEDGE |
3849 FHD F08
4
X24042
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 X24042 this is fixed as 1010[B].
Figure 4. Slave Address
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HIGH |
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ORDER |
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DEVICE TYPE |
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WORD |
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IDENTIFIER |
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ADDRESS |
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1 |
0 |
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0 |
A2 |
A1 |
A0 |
R/W |
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DEVICE |
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ADDRESS |
3849 FHD F09 |
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The next two significant bits addresses a particular device. A system could have up to four X24042 devices on the bus (see Figure 10). The four addresses are defined by the state of the A1 and A2 input.
The next bit of the slave address is an extension of the array’s address and is concatenated with the eight bits of address in the word address field, providing direct access to the whole 512 x 8 array.
Figure 5. Byte Write
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 X24042 monitors the SDA bus comparing the slave address being transmitted with its slave address (device type and state of the A2 and A1 inputs). Upon a correct compare the X24042 outputs an acknowledge on the SDA line. Depending on the state of the R/W bit, the X24042 will execute a read or write operation.
WRITE OPERATIONS
Byte Write
For a write operation, the X24042 requires a second address field. This address field is the word address, comprised of eight bits, providing access to any one of the 512 words in the selected page of memory. Upon receipt of the word address the X24042 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 X24042 begins the internal write cycle to the nonvolatile memory. While the internal write cycle is in progress the X24042 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.
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SLAVE |
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WORD |
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S |
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BUS ACTIVITY: A |
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ADDRESS |
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ADDRESS |
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DATA |
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MASTER |
R |
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P |
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SDA LINE |
S |
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BUS ACTIVITY: |
A |
A |
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C |
C |
C |
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X24042 |
K |
K |
K |
3849 FHD F10
5