U634H256XS

Obsolete - Not Recommended for New Designs www.DataSheet4U.com U634H256XS PowerStore 32K x 8 nvSRAM Die Description The U634H256XS has two separate modes of operation: SRAM mode and nonvolatile mode. In SRAM mode, the memory operates as an ordinary static RAM. In nonvolatile operation, data is transferred in parallel from SRAM to EEPROM or from EEPROM to SRAM. In this mode SRAM functions are disabled. The U634H256XS is a fast static RAM (25, 35, 45 ns), with a nonvolatile electrically erasable PROM (EEPROM) element incorporated in each static memory cell. The SRAM can be read and written an unlimited number of times, while independent nonvolatile data resides in EEPROM. Data transfers from the SRAM to the EEPROM (the STORE operation) take place automatically upon power down using charge stored in an external 100 μF capacitor. Transfers from the EEPROM to the SRAM (the RECALL operation) take place automatically on power up. The U634H256XS combines the high performance and ease of use of a fast SRAM with nonvolatile data integrity. Pad Description STORE cycles also may be initiated under user control via a software sequence or via a single pad (HSB). Once a STORE cycle is initiated, further input or output are disabled until the cycle is completed. Because a sequence of addresses is used for STORE initiation, it is important that no other read or write accesses intervene in the sequence or the sequence will be aborted. RECALL cycles may also be initiated by a software sequence...