ST's parallel real-time clock ICs, also called Timekeepers, combine a SRAM with up to 256 Kbytes of memory and a byte-wide interface along with a quartz-based very-low-power oscillator with a clock/calendar circuit to provide real-time data.
Advanced RTC ICs include additional features such as programmable alarms, watchdog timers, system reset outputs and battery-low warning flags.
Products in through-hole packages (CAPHAT) embed the battery and crystal, while SOIC packages are connected with the battery and crystal using ST’s SNAPHAT® detachable top.
M48T201 devices include a supervisor function that converts external standard low-power SRAM devices into non-volatile memory (NVRAM). They provide control and battery backup to an external low-power SRAM with from 1 to 16 Mbits and with up to 10 years of data retention.