The SST31LF021/021E devices are a 256K x8 CMOS flash memory bank combined with a 128K x8 or 32K x8 CMOS SRAM memory bank manufactured with SST's proprietary, high performance SuperFlash technology. Two pinout standards are available for these devices. The SST31LF021 conform to JEDEC standard flash pinouts and the SST31LF021E conforms to standard EPROM pinouts. The SST31LF021/021E devices write (SRAM or flash) with a 3.0-3.6V power supply. The monolithic SST31LF021/021E devices conform to Software Data Protect (SDP) commands for x8 EEPROMs. Featuring high performance Byte-Program, the flash memory bank provides a maximum Byte-Program time of 20 sec. The entire flash memory bank can be erased and programmed byte-by-byte in typically 4 seconds, when using interface features such as Toggle Bit or Data# Polling to indicate the completion of Program operation. To protect against inadvertent flash write, the SST31LF021/ 021E devices have on-chip hardware and Software Data Protection schemes. Designed, manufactured, and tested for a wide spectrum of applications, the SST31LF021/ 021E devices are offered with a guaranteed endurance of 10,000 cycles. Data retention is rated at greater than 100 years.