U631H256 Datasheet | Simtek

Features ‡ High-performance CMOS nonvolatile static RAM 32768 x 8 bits ‡ 25 ns Access Times ‡ 10 ns Output Enable Access Times ‡ Software STORE Initiation ‡ Automatic STORE Timing ‡ 106 STORE cycles to EEPROM ‡ 100 years data retention in EEPROM ‡ Automatic RECALL on Power Up ‡ Software RECALL Initiation ‡ Unlimited RECALL cycles from EEPROM ‡ Unlimited Read and Write to SRAM ‡ Single 5 V ± 10 % Operation ‡ Operating temperature ranges: 0 to 70 °C -40 to 85 °C ‡ QS 9000 Quality Standard ‡ ESD protection > 2000 V (MIL STD 883C M3015.7-HBM) ‡ Ro HS pliance and Pb- free Package: SOP28 (330 mil) Description The U631H256 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 U631H256 is a fast static RAM (25 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), or from the EEPROM to the SRAM (the RECALL operation) are initiated through software sequences. The U631H256 bines the high performance and ease of use of a fast SRAM with nonvolatile data integrity. 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. 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. The U631H256...