U635H16 Datasheet | Simtek

Features Description The U635H16 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 U635H16 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 system capacitance. Transfers from the EEPROM to the SRAM (the RECALL operation) take place automatically on power up. The U635H16 bines the high performance and ease of use of a fast SRAM with nonvolatile data integrity. STORE cycles also may be initiated under user control via a software sequence. Once a STORE cycle is initiated, further input or output are disabled until the cycle is pleted. 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. Internally, RECALL is a two step procedure. First, the SRAM data is cleared and second, the nonvolatile information is transferred into the SRAM cells. The RECALL operation in no way alters the data in the EEPROM cells. The nonvolatile data can be recalled an unlimited number of times. - - - - - - - - - - - - - - - - - - High-performance CMOS nonvolatile static RAM 2048 x 8 bits 25, 35 and 45 ns Access Times 12, 20 and 25 ns Output Enable Access Times ICC = 15 m A at 200 ns Cycle Time Automatic STORE to EEPROM on Power Down using system capacitance Software initiated STORE (STORE Cycle Time < 10 ms) Automatic STORE Timing 106 STORE cycles to EEPROM...