FEATURES 5MHz clock rate IDLock memory --IDLock first or last page, any 1/4 or lower 1/2 of EEPROM array Low power CMOS --<1�A standby current --<3mA active current during write --<400�A active current during read 2.7V-5.5V operation Built-in inadvertent write protection --Power-up/power-down protection circuitry --Write enable latch --Write protect pin SPI modes x 8 bits --16-byte page mode Self-timed write cycle --5ms write cycle time (typical) High reliability --Endurance: 1,000,000 cycles/byte --Data retention: 100 years --ESD: 2000V on all pins 8-lead MSOP package 8-lead TSSOP package 8-lead SOIC package BLOCK DIAGRAM

SI Data Register SO Y Decode Logic 8 16 SCK Command Decode and Control Logic X Decode Logic 64 8K EERPM Array CS WP Write Control Logic High Voltage Control

The is a CMOS 8K-bit serial EEPROM, internally organized x 8. The X25097 features a Serial Peripheral Interface (SPI) and software protocol, allowing operation on a simple four-wire bus. The bus signals are a clock input (SCK) plus separate data in (SI) and data out (SO) lines. Access to the device is controlled through a chip select (CS) input, allowing any number of devices to share the same bus. IDLock is a programmable locking mechanism which allows the user to lock system ID and parametric data in different portions of the EEPROM memory space, ranging from as little as one page to as much 1/2 of the total array. The X25097 also features a WP pin that can be used for hardwire protection of the part, disabling all write attempts, as well as a Write Enable Latch that must be set before a write operation can be initiated. The X25097 utilizes Xicor's proprietary Direct WriteTM cell, providing a minimum endurance of 1,000,000 cycles per byte and a minimum data retention of 100 years.

PIN DESCRIPTIONS Serial Output (SO) is a push/pull serial data output pin. During a read cycle, data is shifted out on this pin. Data is clocked out by the falling edge of the serial clock. Serial Input (SI) is a serial data input pin. All opcodes, byte addresses, and data to be written to the memory are input on this pin. Data is latched by the rising edge of the serial clock. Serial Clock (SCK) The Serial Clock controls the serial bus timing for data input and output. Opcodes, addresses, or data present on the SI pin are latched on the rising edge of the clock input, while data on the SO pin change after the falling edge of the clock input. Chip Select (CS) PIN NAMES Symbol

It should be noted that after power-up, a HIGH to LOW transition CS is required prior to the start of any operation. When CS is HIGH, the X25097 is deselected and the SO output pin is at high impedance, and unless an internal write operation is underway, the X25097 will be in the standby power mode. CS LOW enables the X25097, placing it in the active power mode.

Write Protect (WP) When WP is LOW, nonvolatile writes to the X25097 are disabled, but the part otherwise functions normally. When WP is held HIGH, all functions, including nonvolatile writes operate normally. WP going LOW while CS is still LOW will interrupt a write to the X25097. If the internal write cycle has already been initiated, WP going low will have no affect on this write.

The x 8 EEPROM designed to interface directly with the synchronous Serial Peripheral Interface (SPI) of many popular microcontroller families.

The X25097 contains an 8-bit instruction register. It is accessed via the SI input, with data being clocked in on the rising edge of SCK. CS must be LOW and the WP input must be HIGH during the entire operation. Table 1 contains a list of the instructions and their opcodes. All instructions, addresses and data are transferred MSB first. Data input is sampled on the first rising edge of SCK after CS goes LOW. SCK is static, allowing the user to stop the clock, and then start it again to resume operations where left off. the 16-bit address, of which the last 10 bits are used (bits [15:10] specified to be zeroes). After the READ opcode and address are sent, the data stored in the memory at the selected address is shifted out on the SO line. The data stored in memory at the next address can be read sequentially by continuing to provide clock pulses. The address is automatically incremented to the next higher address after each byte of data is shifted out. When the highest address is reached (03FFh), the address counter rolls over to address 0000h, allowing the read cycle to be continued indefinitely. The read operation is terminated by taking CS HIGH. Refer to the Read Operation Sequence illustrated in Figure 2. Read Status Operation If there is not a nonvolatile write in progress, the Read Status instruction returns the ID Lock byte from the Status Register which contains the ID Lock bits IDL2IDL0 (Figure 1). The ID Lock bits define the ID Lock condition (Figure 1/Table1). The other bits are reserved and will return `0' when read. See Figure If a nonvolatile write is in progress, the Read Status Instruction returns a HIGH on SO. When the nonvolatile write cycle is completed, the status register data is read out. Clocking SCK is valid during a nonvolatile write in progress, but is not necessary. If the SCK line is clocked, the pointer to the status register is also clocked, even though the SO pin shows the status of the nonvolatile write operation (See Figure 3).

Write Enable Latch The X25097 contains a "Write Enable" latch. This latch must be SET before a write operation is initiated. The WREN instruction will set the latch and the WRDI instruction will reset the latch (Figure 4). This latch is automatically reset upon a power-up condition and after the completion of a byte or page write cycle.

IDLock Memory Xicor's IDLock Memory provides a flexible mechanism to store and lock system ID and parametric information. There are seven distinct IDLock Memory areas within the array which vary in size from one page to as much as half of the entire array. These areas and associated address ranges are IDLocked by writing the appropriate two byte IDLock instruction to the device as described in Table 1 and Figure 7. Once an IDLock instruction has been completed, that IDLock setup is held in a nonvolatile Status Register (Figure 1) until the next IDLock instruction is issued. The sections of the memory array that are IDLocked can be read (but not written) until IDLock Protection is removed or changed. Table 1. Status Register/IDLock Protection Byte 7

Read Sequence When reading from the EEPROM memory array, CS is first pulled LOW to select the device. The 8-bit READ instruction is transmitted to the X25097, followed by

Clock and Data Timing Data input on the SI line is latched on the rising edge of SCK. Data is output on the SO line by the falling edge of SCK.

Write Sequence Prior to any attempt to write data into the X25097, the "Write Enable" latch must first be set by issuing the WREN instruction (See Table 1 and Figure CS is first taken LOW. Then the WREN instruction is clocked into the X25097. After all eight bits of the instruction are transmitted, CS must then be taken HIGH. If the user continues the write operation without taking CS HIGH after issuing the WREN instruction, the write operation will be ignored. To write data to the EEPROM memory array, the user then issues the WRITE instruction, followed by the 16 bit address and the data to be written. Only the last 10 bits of the address are used and bits [15:10] are specified to be zeroes. This is minimally a thirty-two clock operation. CS must go LOW and remain LOW for the duration of the operation. The host may continue to write to 16 bytes of data to the X25097. The only