M48T35, M48T35Y are TIMEKEEPER® SRAMs produced by Microchip Technology with 256 Kbit (32Kb x8) capacity, which integrate an ultra-low-power SRAM, real-time clock, power-fail control circuit and battery. It features byte-wide RAM-like clock access, BCD coded year, month, day, date, hours, minutes and seconds, frequency test output for real-time clock, automatic power-fail chip deselect and write protection, write protect voltages of 4.5V ≤ VPFD ≤ 4.75V, 4.2V ≤ VPFD ≤ 4.5V, self-contained battery and crystal in the CAPHAT DIP package, SOIC package provides direct connection to a SNAPHAT housing containing the battery and crystal, SNAPHAT® housing (battery and crystal) is replaceable, and is pin and function compatible with JEDEC standard 32Kb x8 SRAMs.