Document
32K
X24321
400 KHz 2-Wire Serial E2PROM
4K x 8 Bit
FEATURES
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1.8V to 3.6V, 2.5V to 5.5V and 4.5V to 5.5V Power Supply Operation Low Power CMOS —Active Read Current Less Than 1mA —Active Write Current Less Than 3mA —Standby Current Less Than 1µA 400KHz Fast Mode 2-Wire Serial Interface —Down to 1.8V —Schmitt Trigger Input Noise Suppression —Output Slope Control for Ground Bounce Noise Elimination Internally Organized 4K x 8 Bit 32 Byte Page Write Mode —Minimizes Total Write Time Per Byte Hardware Write Protect Bidirectional Data Transfer Protocol Self-Timed Write Cycle —Typical Write Cycle Time of 5ms High Reliability —Endurance: 1,000,000 Cycles —Data Retention: 100 Years 8-Lead SOIC
DESCRIPTION The X24321 is a CMOS Serial E2PROM Memory, internally organized 4K x 8. The device features a serial interface and software protocol allowing operation on a simple two wire bus. The bus operates at 400KHz all the way down to 1.8V. Three device select inputs (S0–S2) allow up to eight devices to share a common two wire bus. Hardware Write Protection is provided through a Write Protect (WP) input pin on the X24321. When the WP pin is HIGH, the upper quadrant of the Serial E2PROM array is protected against any nonvolatile write attempts. Xicor Serial E2PROM Memories are designed and tested for applications requiring extended endurance. Inherent data retention is greater than 100 years.
FUNCTIONAL DIAGRAM
SERIAL E2PROM DATA AND ADDRESS (SDA)
DATA REGISTER Y DECODE LOGIC COMMAND DECODE AND CONTROL LOGIC
SCL
PAGE DECODE LOGIC
S2 S1 S0 DEVICE SELECT LOGIC WRITE PROTECT LOGIC
E2PROM ARRAY 4K x 8
WP
WRITE VOLTAGE CONTROL
7040 FM 01
©Xicor, 1995, 1996 Patents Pending 7040 3/27/97 T0/C0/D0 SH
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Characteristics subject to change without notice
X24321
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 Pullup resistor selection graph at the end of this data sheet. Device Select (S0, S1, S2) The device select inputs (S0, S1, S2) are used to set the first three bits of the 8-bit slave address. This allows up to eight devices to share a common bus. These inputs can be static or actively driven. If used statically they must be tied to VSS or VCC as appropriate. If actively driven, they must be driven with CMOS levels. Write Protect (WP) The Write Protect input controls the Hardware Write Protect feature. When held LOW, Hardware Write Protection is disabled and the device can be written normally. When this input is held HIGH, Write Protection is enabled, and nonvolatile writes are disabled to the upper quadrant of the E2PROM array. PIN NAMES Symbol
S0, S1, S2 SDA SCL WP VSS VCC
Description
Device Select Inputs Serial Data Serial Clock Write Protect Ground Supply Voltage
7040 FRM T01
PIN CONFIGURATION
8-LEAD SOIC S0 S1 S2 VSS 1 2 3 4 X24321 8 7 6 5 VCC WP SCL SDA
7040 FM 02
2
X24321
DEVICE OPERATION The device 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 device 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. Start Condition All commands are preceded by the start condition, which is a HIGH to LOW transition of SDA when SCL is HIGH. The device continuously monitors the SDA and SCL lines for the start condition and will not respond to any command until this condition has been met.
Figure 1. Data Validity
SCL
SDA DATA STABLE DATA CHANGE
7040 FM 03
Figure 2. Definition of Start and Stop
SCL
SDA START BIT STOP BIT
7040 FM 04
3
X24321
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 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. Acknowledge Acknowledge is a software convention used to indicate successful data transfer. The transmitting device, either master or slave, 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. Figure 3. Acknowledge.