The bq4842Y RTC Module is a non-volatile 1,048,576-bit SRAM organized as 131,072 words by 8 bits with an integral accessible real-time clock and CPU supervisor. The CPU supervisor provides a programmable watchdog timer and a microprocessor reset. Other features include alarm, power-fail, and periodic interrupts, and a battery-low warning. The device combines an internal lithium battery, quartz crystal, clock and power-fail chip, and a full CMOS SRAM in a plastic 32-pin DIP module. The RTC Module directly replaces industry-standard SRAMs and also fits into many EPROM and EEPROM sockets without any requirement for special write timing or limitations on the number of write cycles. Registers for the real-time clock, alarm and other special functions are located in registers 1FFF0h? 1FFFFh of the memory array. The clock and alarm registers are dual-port read/write SRAM locations that are updated once per second by a clock control circuit from the internal clock counters. The dual-port registers allow clock updates to occur without interrupting normal access to the rest of the SRAM array. The bq4842Y also contains a power-fail-detect circuit. The circuit deselects the device whenever VCC falls below tolerance, providing a high degree of data security. The battery is electrically isolated when shipped from the factory to provide maximum battery capacity. The battery remains disconnected until the first application of VCC.