memory products - Al Kossow's Bitsavers

MKI48Z02112(B)-15/20/25DATA RETENTION MODEWith Vee applied, the MKI48Z02I12 operates as aconventional BYTEWIDE static ram. However, Veeis being constantly monitored. Should the supplyvoltage decay, the RAM will automatically powerfaildeselect, write protecting itself when Vee fallswithin the VPFD (max), VPFD (min) window. TheMK148Z02 has a VPFD (max) to VPFD (min) windowof 4.75 volts to 4.5 volts, providing very high datasecurity, particularly when all of the other systemcomponents are specified to 5.0 volts plus and minus10%. The MKI48Z12 has a VPFD (max) to VPFD(min) window of 4.5 volts to 4.2 volts, allowing usersconstrained to a 10% power supply speCificationto use the device.FIGURE 5. CHECKING THE BOK FLAG STATUSREAD DATAAT ANYADDRESSNote: A mid-write cycle power failure may corruptdata at the current address location, but does notjeopardize the rest of the RAM's content. N. voltagesbelow VPFD (min), the user can be assured thememory will be in a write protected state, providedtheycc_ ~all time does not exceed tF. TheMKI48Z02/12 may respond to transient noise spikesthat reach into the deselect window if they shouldoccur during the time the device Is sampling Vex;.Therefore decoupling of power supply lines ISrecommended.The power switching circuit connects external Veeto the RAM and disconnects the battery when Veerises above Vso' As Vee rises the battery voltageis checked. If the voltage is too low, an internal BatteryNot OK (Brn