The iButton is a high-performance, rugged, and rewritable non-volatile data storage device. It features 4096 bits of read/write non-volatile memory, 256-bit scratchpad, real-time clock/calendar, interval timer, programmable cycle counter, programmable alarms, write protect, programmable expiration date, a clock accuracy of ±2 minutes/month at 25°C, an operating temperature range of -40°C to +70°C, and over 10 years of data retention.