93LCS56/93LCS66 pdf datasheet

The Microchip Technology Inc. 93LCS56/66 are low voltage
Serial Electrically Erasable PROMs with memory
capacities of 2K bits/4K bits respectively. A write protect
register is included in order to provide a user defined
region of write protected memory. All memory locations
greater than or equal to the address placed in the write
protect register will be protected from any attempted write
or erase operation. It is also possible to protect the
address in the write protect register permanently by using
a one time only instruction (PRDS). Any attempt to alter
data in a register whose address is equal to or greater
than the address stored in the protect register will be
aborted. Advanced CMOS technology makes this device
ideal for low power non-volatile memory applications.