DESCRIPTION
The X24640 is a CMOS Serial E2PROM, internally organized 8K x 8. The device features a serial interface and software protocol allowing operation on a simple two wire bus. The bus operates at 400 KHz 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. A Write Protect Register at the highest address location, FFFFh, provides three write protection features: Software Write Protect, Block Lock Protect, and Programmable Hardware Write Protect. The Software Write Protect feature prevents any nonvolatile writes to the device until the WEL bit in the Write Protect Register is set. The Block Lock Protection feature gives the user four array block protect options, set by programming two bits in the Write Protect Register. The Programmable Hardware Write Protect feature allows the user to install the device with WP tied to VCC, program and Block Lock the desired portions of the memory array in circuit, and then enable the In Circuit Programmable ROM Mode by programming the WPEN bit in the Write Protect Register. After this, the Block Locked portions of the array, including the Write Protect Register itself, are permanently protected from being erased.

FEATURES
• Save Critical Data with Programmable Block Lock Protection
   —Block Lock (0, 1/4, 1/2, or all of E2PROM Array)
   —Software Program Protection
   —Programmable Hardware Write Protect
• In Circuit Programmable ROM Mode
• 400KHz 2-Wire Serial Interfac
   —Schmitt Trigger Input Noise Suppression
   —Output Slope Control for Ground Bounce Noise Elimination
• Longer Battery Life With Lower Power
   —Active Read Current Less Than 1mA
   —Active Program Current Less Than 3mA
   —Standby Current Less Than 1µA
• 1.8V to 3.6V, 2.5V to 5.5V and 4.5V to 5.5V Power Supply Versions
• 32 Word Page Write Mode
   —Minimizes Total Write Time Per Word
• Internally Organized 8K x 8
• Bidirectional Data Transfer Protocol
• Self-Timed Write Cycle
   —Typical Write Cycle Time of 5ms
• High Reliability
   —Endurance: 100,000 Cycles
   —Data Retention: 100 Years
• 8-Lead SOIC
• 20-Lead TSSOP
• 8-Lead PDIP