The X25F064/032/016/008 family are 8/16/32/64K-bit CMOS SerialFlash memory, internally organized X 8. They feature a "Univolt" Program and Read voltage, Serial Peripheral Interface (SPI), and software protocol allowing operation on a simple three-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. The X25F064/032/016/008 also features two additional inputs that provide the end user with added flexibility. By asserting the HOLD input, the X25F064/032/016/008 will ignore transitions on its inputs, thus allowing the host to service higher priority interrupts. The PP input can be used as a hardwire input to the X25F064/032/016/008 disabling all program attempts to the status register, thus providing a mechanism for limiting end user capability of altering 0, 1/4, 1/2, or all of the memory. The X25F064/032/016/008 utilizes Xicor's proprietary flash cell, providing a minimum endurance of 100,000 cycles and a minimum data retention of 100 years.